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Old 07-15-2018, 02:10 PM   #21
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A few more, Hard to read teh temp probe in some pics.
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Old 07-15-2018, 02:14 PM   #22
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In case you cant tell from the pics the "Green" range on my temp gauge (Which mean the "Ideal vent temp for "Car AC units") is from 40 to 45 deg. Mine just makes the 45 deg range. But my car is at like 37 deg when tested!
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Old 07-15-2018, 02:58 PM   #23
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Originally Posted by Long & Winding road View Post
Here is a few pics of the insulation on the roof and temp gauge inside vent.
What kind of insulation is that and do I see aluminum tape too? Thanks.
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Old 07-16-2018, 02:06 AM   #24
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What kind of insulation is that and do I see aluminum tape too? Thanks.
Yes, Aluminum tape and Frost King Duct insulation (which is self adhesive). But under all that I used some left over Fat Mat (the thiner kind like Dynomat) on the top and the front sloped side only - not sure If I would do the entire box with Fat Mat for the cost to benifit ratio.

Plus I used zip ties on the pipe insulation since over time I was afraid the small self adhesive strip will let go and I dont want it to get caught up in the fan blades.
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Old 07-16-2018, 05:12 PM   #25
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I'm glad this thread came back around. I've been thinking about having a look at sealing &/or insulating my plenum a bit better...and also painting my outer cowl white instead of the black it is now.

But re-reading this thread, maybe I just missed it, but I see lots of mention of various discharge air temperatures... but I'm thinking that probably really isn't the whole picture. The difference between the temperature at the air return vs the discharge is what you want to look at. Generally a delta of approx 15-20 degrees F (as I recall) is what you'll see if properly operating.

I'm curious if these mods being discussed increased the delta at all?
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Old 07-16-2018, 07:58 PM   #26
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I'm glad this thread came back around. I've been thinking about having a look at sealing &/or insulating my plenum a bit better...and also painting my outer cowl white instead of the black it is now.

But re-reading this thread, maybe I just missed it, but I see lots of mention of various discharge air temperatures... but I'm thinking that probably really isn't the whole picture. The difference between the temperature at the air return vs the discharge is what you want to look at. Generally a delta of approx 15-20 degrees F (as I recall) is what you'll see if properly operating.

I'm curious if these mods being discussed increased the delta at all?
Yes, I know they say "20 deg temp diff and your AC is working fine". But I disagree with that after I did my mods. (But I might have been just lucky with my results).

I thew all that out the window and concentrated on making the outgoing temp as cold as possible + rejecting as much heat as possible so the AC can do its job.

I say try to get as much as you can out of any AC unit as long as it dont frost up. Why limit yourself (or accept) 20 deg? Plus I ask myself why does my 15 year old car AC put out 37 to 40 deg and the RV is only 65 deg?

Yesterday I cranked up the AC (RV was out in full sun) and my thermostat showed 96 deg in the bedroom so put my temp probe in the vent under the direct cold air flow and 10 min later and it showed 45 deg! I dont know exact inlet temp but it had to be close to 96 deg. Thats 51 deg differences!! Even if around the AC it was cooler like 90 that still 45 deg. And I really dont care what the inlet is as long as the output is 45 deg! LOL.

So I set my timer and at 30 minutes it dropped 5 deg (91) then 30 more mintues it was at 85 deg. I we loaded up for a picnic with my 84 year old mother and with the cab AC and roof AC running full blast 30 minutes later we were at 74 deg in the middle of the RV and 76 in the bedroom. Im happy with my results. We stopped and I pulled the curtains to block the two front cockpit windows (left the front windsheild open) and the temp dropped to 72 deg in the kitchen area and 73 in the back (but that was about an hour later).

Full sun the entire time, 93 deg outside temp with high humidity.

Last year I suffered along because mine was only doing about 65 deg out temp but it would never cool the RV below 82 degrees with ALL of the windows blacked out with reflective bubbles (in full sun). I dont even use the bubble now (Pain in the rear) unless im parked in one spot for half a day or more - Even then I like to have a view so I will remove if no direct sun comming in.

But like they say results may vary and the cockpit area is warmer by the front window but not bad.

I need to put by temp gage on the coffee table between the camptains chairs for my next test.

And then the final test I will use all my bubbles and black out all windows and see if I can get into the 60's! Burr. Might use entire the RV for a frig when we have company over. LOL
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Old 07-16-2018, 08:28 PM   #27
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This is awesome info. I have (2) rooftop A/C's in my Windsport 34J (35.7') and I had both on prepping to leave for a weekend trip. Both on for 4 hrs and the coach was in direct sunlight in 98-100F California heat. IT still was above 80 when we left in the coach. I have no Bubbles just shades drawn. RV Facing East. Going to use my front A/C as my test case. I could win (2) ways. More Comfortable RV and a happier Wife!! BONUS!
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Old 07-16-2018, 08:35 PM   #28
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Yep, win win. LOL.

I would get some bubbles for the windows or have them all tinted (factory tint does nothing to reject heat). See my Cermic window tint thred.

Let us know your outcome.
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Old 07-17-2018, 05:16 AM   #29
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Just ran a test on my front A/C. Now mine are 13.5k BTU units so I would expect a little lower performance. IT was 105F in my coach. No sun on RV did it at dusk. The sensor was about halfway up on the far left side (looking up through air intake) of my core.
Pulled and tied to hang in the air intake path. Could only reach 65F on discharge through the slide vent on rear of A/C. A Delta T of about 21-22F. After about 40mins. Going to move the sensor to the middle about 4-5" from the bottom and insulate the roof top air box hopefully that will get me a discharge below 60 Deg. F. I really want to get to at least 55 Deg. F.
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Old 07-17-2018, 05:49 AM   #30
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Originally Posted by Kake95 View Post
Just ran a test on my front A/C. Now mine are 13.5k BTU units so I would expect a little lower performance. IT was 105F in my coach. No sun on RV did it at dusk. The sensor was about halfway up on the far left side (looking up through air intake) of my core.
Pulled and tied to hang in the air intake path. Could only reach 65F on discharge through the slide vent on rear of A/C. A Delta T of about 21-22F. After about 40mins. Going to move the sensor to the middle about 4-5" from the bottom and insulate the roof top air box hopefully that will get me a discharge below 60 Deg. F. I really want to get to at least 55 Deg. F.
Great. Let us know your outcome. Hopefully you can get to 45 to 50 deg output temp. If not try leaving your probe loose like another member suggested.

Dont forget to seal or tape the insulation wall that separates the hot from the cold side. Its right in the middle of the AC unit looking straight up. Mine had a few small leaks along the "walls" and could move very easy - so all of the mods add up over time. Others had said it was leaning sideways and leaking major cold air into the warm side so the unit thinks it colder than what it actully is inside the RV.
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Old 07-18-2018, 01:40 AM   #31
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Originally Posted by Long & Winding road View Post
I been wanting to share this for 4 weeks so I finally joined the forum today so I can share some of my success stories. This is my most satisfying (and cheapest) so far.

This might be a bit long winded for my first post but I wanted to tell the entire problem and my solution so please read along. I have read about this same exact problem 20 times + on this forum so I hope it helps others. It might save you $800 - $1000 over installing a 2nd AC unit so might be worth a try - you decide.

I will "try" and keep my other posts about my other mods more brief. (I said "try" LOL). And before you ask I will try and post some pictures later.

When I purchased my 2017 Axis brand new the 15000 BTU AC was not cold enough and was driving me crazy. The best it would do was around 85 - 87 deg inside temp after being on all day in the hot sun (95 deg + outside) while driving or parked at the “trail head” (Mtn biker here). At first I thought it was not the AC's fault and I fitted all of my windows with bubble wrap like I read on this forum (thanks to Jerry' Hurricane Mods and many others), added the extra AC cold air vent on cover, then inserted roof vent foam inserts to block all the heat that I could. That helped some (Maybe 82 deg at best) but not enough and took forever to get down to this temp once the RV heated up.

So right before I had a few things done on my punch list this spring (but after I fixed 20 + items myself first) one of the Camping World employees at service desk gave me a useful tip (imagine that- LOL) that I have NOT read on ANY forum or in any of my many searches on this subject.

He said to move the temp probe ("Thermistor probe") up a little to see if that would help but not too much so the unit don’t frost up. So after researching on that topic for a few weeks I thought I would try a few things myself before I have CW tear into it.

At first I decided insulated the AC box (on roof) really well with left over Dynomat and Frost King duct insulation (I did the entire aluminum ductwork under the plastic cover on roof). Then I used the foam rubber pipe insulation on the exposed AC copper pipes to prevent frosting up. Left it like this for a week or so - This helped some but I was really doing this to help with the 2nd mod I was planning. So I took out my automotive AC thermometer and stuck it directly in the cold air path inside RV at AC cover - it was reading about 65 deg. Small improvement (but im not sure by how much since I didn’t take a before temp – sorry).

For 2nd part of this job I removed the inside cover and used aluminum duct tape to seal up leaky ductwork and added some half inch soft foam to insulate between cover to the duct work (many small leaks - im sure this helped a lot - check yours now!).

3rd part of AC mod - I moved temp probe up about two inches or so. Make sure it contacts the coil inside fins by slide it in and then down slowly until it stops at coil. You can see this probe on the cold air return side (this is inside the RV looking up for a single white wire with metal probe stuck in the aluminum fins about one inch from the bottom - which by the way is the location the manufacture recommends - I checked. So this might void your warrantee (move it back before AC service?)).

Now tested the cold air duct again and it was down to 55 deg! I tried it out for a day and I was able to get the inside of the RV down to like 76 deg or so. Big improvement. But the next day I thought "we can do better" and "My car AC show 35 deg at the vents why only 55 deg on the rv?" so I moved the probe up another 1.5 inches (about 4 inches total – which was about the max you should go according to my research – make sure you do your own research.) and then I checked with my temp probe - It was 45 DEG NOW!! Wow. I thought that was great and I better leave it alone - don’t want to frost up the coils or screw something else up.

Final results = 75 temp in inside of RV now on 90 - 95 deg days sitting in full sun!!!! And that’s WITHOUT BUBBLE WRAP on windows!! (70 -72 in shade).

And 70 – 73 degrees in full sun with my new “ceramic window tint” (that will be a later post – highly recommend).

Success!!

I been testing it for a few weeks now before I posted this so I knew it worked well and has NOT frosted up on me. I even went on the roof to check coils/pipes after two hours full blast and not one sign of frosting up, then I check again at 4 hours - looks normal. I also removed inside cover and looked around - no frost – even on hot humid days.

We did several day trips (and one weekend) with AC unit on for 2 - 5 hours at a time and it worked perfectly. And on the 4th of July it was on for 10 hours straight and worked perfectly the entire time.

So now when turn on the AC and the RV is hot inside (90 - 100 deg!) in 45 minutes its down to 82 - 84 deg next to kitchen sink (were I keep a digtal gauge) and 72 - 74 deg in 1.5 - 2 hours! The thermostate is in the bedroom and it will show about 2 - 3 degrees warmer temp then the kitchen. Eventally it will equalize temp with all roof ducts open. It has not problem maintaining 73 - 75 deg at any given time with door opening up some and windows not covered or shade pulled down (after my window tint) or driving down the road on a sunny days. Its been realativly cool this year (90 -92) so if its 100 outside Im sure my readings will differ some.

My 4th AC mod was installing he Coleman Mach digital thermostat (I highly recommend). Really make the system work well.

I hope this helps a few of you guys either suffering with inadequate AC units or thinking of adding a 2nd AC unit.

I hope I didn’t bore you on my first post - I thought I should explain it fully so you can decide if you want to modify yours. Im not telling you how to do it – just telling you how I did mine and you take full responsibility if something goes Wrong.

Happy trails
first off... I am willing to throw everything I know, or think I know out the window to learn something new....the probe deal...seems to me that it is a temp sensor that senses 32 degrees and shuts the compressor down..... sound about right???? and the AC is a cold / heat exchanger.... right... meaning the Freon comes in to the evap cold, the warm air inside blows across the evap and cools and blows out the service duct... the hot Freon goes then to the condenser...where it is cooled... then back to get re compressed, making it cold again... sound about right???? so the probe does nothing till the evap gets to 32 degrees.... right???so would you mind giving more imput that I obviously don't have....how would moving the probe up or down do any thing, unless you were freezing up the coils???next,... the very most efficient...is a 22 degree split.... your say'n that you are getting a 27 degree split... but @ 90 degree ambient temp, 72 is only a 18 degree temp drop...
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Old 07-18-2018, 02:09 AM   #32
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Originally Posted by Long & Winding road View Post
Yes, I know they say "20 deg temp diff and your AC is working fine". But I disagree with that after I did my mods. (But I might have been just lucky with my re

I say try to get as much as you can out of any AC unit as long as it dont frost up. Why limit yourself (or accept) 20 deg? Plus I ask myself why does my 15 year old car AC put out 37 to 40 deg and the RV is only 65 deg?

Yesterday I cranked up the AC (RV was out in full sun) and my thermostat showed 96 deg in the bedroom so put my temp probe in the vent under the direct cold air flow and 10 min later and it showed 45 deg! I dont know exact inlet temp but it had to be close to 96 deg. Thats 51 deg differences!! Even if around the AC it was cooler like 90 that still 45 deg. And I really dont care what the inlet is as long as the output is 45 deg! LOL.

So I set my timer and at 30 minutes it dropped 5 deg (91) then 30 more mintues it was at 85 deg. I we loaded up for a picnic with my 84 year old mother and with the cab AC and roof AC running full blast 30 minutes later we were at 74 deg in the middle of the RV and 76 in the bedroom. Im happy with my results. We stopped and I pulled the curtains to block the two front cockpit windows (left the front windsheild open) and the temp dropped to 72 deg in the kitchen area and 73 in the back (but that was about an hour later).

Full sun the entire time, 93 deg outside temp with high humidity.

Last year I suffered along because mine was only doing about 65 deg out temp but it would never cool the RV below 82 degrees with ALL of the windows blacked out with reflective bubbles (in full sun). I dont even use the bubble now (Pain in the rear) unless im parked in one spot for half a day or more - Even then I like to have a view so I will remove if no direct sun comming in.

But like they say results may vary and the cockpit area is warmer by the front window but not bad.

I need to put by temp gage on the coffee table between the camptains chairs for my next test.

And then the final test I will use all my bubbles and black out all windows and see if I can get into the 60's! Burr. Might use entire the RV for a frig when we have company over. LOL
Quote:
Originally Posted by Long & Winding road View Post
I say try to get as much as you can out of any AC unit as long as it dont frost up. Why limit yourself (or accept) 20 deg? Plus I ask myself why does my 15 year old car AC put out 37 to 40 deg and the RV is only 65 deg?

so I will answer you question.... the reason the car works as it does, the condenser and the fan, that and air flow over bigger condenser.. the roof ac has poor at best condenser cooling so the Freon stays hotter...then compresses at a higher temp...that and multiple more air space..
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Old 07-18-2018, 03:25 AM   #33
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Originally Posted by vegasruv24.1 View Post
so I will answer you question.... the reason the car works as it does, the condenser and the fan, that and air flow over bigger condenser.. the roof ac has poor at best condenser cooling so the Freon stays hotter...then compresses at a higher temp...that and multiple more air space..
Ok great. Makes sense to me.

Why dosent Colman make a roof ac better? Perhaps longer or wider (Hate to go taller) to allow two condensers and two fans? Even it it cost $100 or $200 more but can put out 18000 BTU it would be worth it IMO.

Good point.
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Old 07-18-2018, 03:57 AM   #34
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Ok great. Makes sense to me.

Why dosent Colman make a roof ac better? Perhaps longer or wider (Hate to go taller) to allow two condensers and two fans? Even it it cost $100 or $200 more but can put out 18000 BTU it would be worth it IMO.

Good point.
here's the wall that they are up against....30 amp power for the whole rig...to make the unit put out more, more power consumption...the biggest problem with rv 's is the R value of the coach...with the square foot of exterior exposed to direct sunlight, the available cooling just doesn't get it done... they need to build RV's in havasu and vegas to figure out that one ac won't cool 30 foot coaches,,, most struggle with two..when I lived in central California, temp was with in 20 degrees of 70 year round...we didn't even have an AC...and it would cool down at night... in havasu it's over 100 degrees at night at 1am...
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Old 07-18-2018, 04:13 AM   #35
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Originally Posted by vegasruv24.1 View Post
first off... I am willing to throw everything I know, or think I know out the window to learn something new....the probe deal...seems to me that it is a temp sensor that senses 32 degrees and shuts the compressor down..... sound about right???? and the AC is a cold / heat exchanger.... right... meaning the Freon comes in to the evap cold, the warm air inside blows across the evap and cools and blows out the service duct... the hot Freon goes then to the condenser...where it is cooled... then back to get re compressed, making it cold again... sound about right???? so the probe does nothing till the evap gets to 32 degrees.... right???so would you mind giving more imput that I obviously don't have....how would moving the probe up or down do any thing, unless you were freezing up the coils???next,... the very most efficient...is a 22 degree split.... your say'n that you are getting a 27 degree split... but @ 90 degree ambient temp, 72 is only a 18 degree temp drop...

I thought you were throwing away the rules with me. LOL.

I didnt look at any "splits" or "Deltas" or even "Flux Capacitors". LOL . Im not trying to explain why mine works better Im just telling you what I did to mine and the results I had in hopes it can help others.

All im saying is im getting 18 - 22 degree drop in temperature (from my: uncertified wall thermosat, digtal thermometer in kitchen area and my Auto Zone AC temp probe) consistently.

I don’t know all the fundamentals or have any expertise in HVAC. I don’t have all the answers (I sure wish I did).

All I know is I insulated the cold air return box on the roof, used pipe insulation on the copper tubing on roof and moved my Thermistor probe up about 4 inches and my cold air OUTPUT temp when from 65 deg (at best) last year to 45 degrees (consistanly) this year (with all 3 mods).

It may not work for you but it don’t cost anything to move the probe and its totally reversible so why not try it?

Beside you might find you had a small leak from the cold side over to the warm intake side.

Perhaps with just me fixing my small cold air leak I would have been at 55 degrees last year (which might be normal??) and I only realized a 10 degree again this year.

Why dont we all test our output temps and post hear. (before and after mods) That way we know what the Average norm should be, what the average gain is with diff mods. Just make reference which brand AC you have and BTU output your unit(S) have so we can compare apples to apples.

I think the answer to your 32 degree temp is this two fold:

A: Perhaps the AC stops at "32 deg"... perhaps it stops when it gets to "45" degees? Now See B.

B: Perhaps mine is doing so much better because the ends of the condenser cool quicker (45 deg?) so my unit was sensing it was "cold enough" (it was one inch from the bottom orginally) but now that I moved it up about 4 inches and its in a warmer spot (but unit wants max cool because air is still warm) and now more of the condenser is cooler (Now 32 deg over more coils) so the warm air is getting even colder and it helping drop the output temp?

Maybe? But another post a couple of days ago suggested this was wrong so im just grasping since your looking for answers.

I dont know the answers, I dont even question them anymore.... Im just ejoying the results I have on my unit.

Thow out the "Rules" and just Try it and let us know your outcome.

Im sure in not alone in this. I would love to hear about all the temps and the tricks that we all have for the AC system.

Enjoy the cool breeze and think of of the poor soles without RVs to tinker with.
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Old 07-18-2018, 04:15 AM   #36
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Originally Posted by vegasruv24.1 View Post
here's the wall that they are up against....30 amp power for the whole rig...to make the unit put out more, more power consumption...the biggest problem with rv 's is the R value of the coach...with the square foot of exterior exposed to direct sunlight, the available cooling just doesn't get it done... they need to build RV's in havasu and vegas to figure out that one ac won't cool 30 foot coaches,,, most struggle with two..when I lived in central California, temp was with in 20 degrees of 70 year round...we didn't even have an AC...and it would cool down at night... in havasu it's over 100 degrees at night at 1am...
I new sombody would have the answer! Im going with this. But I bet they could fudge 16000 BTU for me on my next unit. LOL.
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Old 07-18-2018, 04:26 AM   #37
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Where in Cental Ca did you live? I wish it was only 90 in the summer in Cental CA.
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Old 07-18-2018, 04:29 AM   #38
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I thought about this the other day when I saw a Hurricane at CW. The Axis and Vegas have to be the WORST class A RV to cool (at least in the Thor lineup).

That front window is not only huge it curves up to the sky allowing more sun and heat in at more hours per a day than the realatively flat windshield of the Hurricane.

PLUS we have TWICE the size SIDE window length in the cockpit since we have to sit further back with the design of our RV and seat placement. In the Hurricane you sit further up (about a foot or 2? Somebody get a tape measure out - lol) so it has a foot (or two) less side window lenght in cockpit than mine.

But that gives the Hurricane a foot or two more living space instead of the massive front dash of the Axis or Vegas. (But the Hurricane has a larger dog house since the engine intrudes more in living space).

Just something to think about.

Single pane glass has a terrable R value and we have more of it in a Axis / Vegas.

Just something to think about

So all of you guys with Hurricane / Windsport / Challenger etc with your fancy "Two units" need to do these modes and post your temps with your single digits results. LOL.
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Old 07-18-2018, 05:37 AM   #39
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first off... I am willing to throw everything I know, or think I know out the window to learn something new....the probe deal...seems to me that it is a temp sensor that senses 32 degrees and shuts the compressor down..... sound about right???? and the AC is a cold / heat exchanger.... right... meaning the Freon comes in to the evap cold, the warm air inside blows across the evap and cools and blows out the service duct... the hot Freon goes then to the condenser...where it is cooled... then back to get re compressed, making it cold again... sound about right???? so the probe does nothing till the evap gets to 32 degrees.... right???so would you mind giving more imput that I obviously don't have....how would moving the probe up or down do any thing, unless you were freezing up the coils???next,... the very most efficient...is a 22 degree split.... your say'n that you are getting a 27 degree split... but @ 90 degree ambient temp, 72 is only a 18 degree temp drop...
Vegasruv24.1- I got your PM but was preoccupied today.

I like what you first said here, being willing to throw out something you thought you knew to learn something else is the sign of a smart person. I know I've had a whole pile of things I THOUGHT were one way, only to learn they were another. It pays to have an open mind, that's for sure.

So the biggest thing I can say is I THINK the thermistor isn't letting it get anywhere near 32 degrees. That's the key here. This is what I mentioned earlier here...
Quote:
It seems to me that Coleman is pretty conservative on their evaporator icing prevention strategies. I think they're cycling the compressor at temps that are way too high.
What if they were cycling back the compressor at temps that are way higher than 32 degrees? H#ll, I don't even know if these compressors are variable displacement, expansion valve or orifice tube systems. I never got that far into bothering to find out more about the compressors themselves. Anyway they do it, they clearly have evaporator icing feedback because they have a thermistor. So they can be as aggressive or as conservative as they want with those strategies. What I did by removing the thermistor from the evap core was basically being as aggressive as you can be on the compromise between low output temps and chance of icing.

I do know this... Coleman has to be SUPER conservative on their units because the same design/calibrations have to work "OK" on hundreds of different applications. It's very similar to what I said in the 5 Star tuning thread, the way Ford has to be VERY conservative on how they calibrate the engine operation on an engine that has to be used in hundreds of different situations and conditions.

This is important because it means there's the strong possibility of major improvements in efficiency in your (ours, or anyone else's) particular situation. If Coleman makes an RV roof air that they absolutely don't want to ice up because it would result in bad customer experiences, they have to make sure it won't ice up in the worst possible situations. I personally want the compromise to be maximum cooling and would simply avoid the "worst possible situations". Like closing all the vents or leaving the AC run all night, or running it non-stop when it's not that hot out.

BTW where did you come up with a "22 degree split" being the "very most efficient"? Just curious. I've had aftermarket dash AC's in cars and motorhomes that would turn the evap core into a giant ice cube in 100+ degree weather. Easily putting out 30 or even 40 degree temp drops from inlet to outlet.

If I get bored, I'll get you guys some actual real data. I can monitor the AC amp draw in my Vegas. All I have to do is put the thermistor in a glass of water and see at what temp the compressor cycles or changes displacement. I'd start with ice water, moving up the temp to find out EXACTLY how cold they let the evaporator core get. Or you guys can just be crazy and try what I suggested. Just pull the thermistor out of the evap core and see what happens. Sometimes you just have to throw theory and debate out and experiment blindly.
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Old 07-18-2018, 12:01 PM   #40
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Brand: Thor Motor Coach
Model: Axis 24.1
State: Michigan
Posts: 9,025
THOR #1150
I have a couple of points/observations/etc.:
1. Speaking of that large window on the Axis/Vegas units (or any large window on any class A): Just cover it from the outside (A Sunguard or Magneshade cover). They keep a lot of the heat out, and look pretty good. (I have a Sunguard--you can immediately feel the difference inside when I put it on.) Granted they don't work while driving but while camping they are great (as a bonus people can't see into the fishbowl in the daytime).

2. The temperature sensor: Why not just run the A/C for a while and then use one of those laser thermometer's to find the warmest spot on the coils then just put the sensor there.
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