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Old 07-25-2019, 01:37 PM   #1
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Model: Quantum
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THOR #11726
Unhappy AC not keeping up

We have a quantum LF31 with 14,000 miles on it. The AC doesn't seem to be keeping up. Here's the back story. DH replaced the analog thermostat with a digital one. All seems ok with that. We have been on a trip starting from our home in Georgia, staying a week in Indiana. The AC seemed fine there. We have moved on to St. Louis, Colorado Springs, Utah national parks, Arizona (temps there were 105) and now in New Mexico. The unit only cools about 5-7 degrees from the outdoor temp. The filters are clean. We we had a"tech" come to our campsite, and he basically told us about clean filters and how to insulate the coach. What a waste of $$. So, any ideas what is the problem with our unit? My husband believes it's ok because it's blowing cold air. Am I just imagining things, or should it at least be keeping it 10-15 degrees cooler than outside? Any help is appreciated!
We have already moved the thermistor, and it is dangling. No help so far.
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Old 07-25-2019, 01:56 PM   #2
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THOR #1150
You may want to read this lengthy thread:
Try this first before you buy 2nd AC unit or bring your unit in for AC service.

As mentioned in that thread there are a few quick and easy checks you can do to improve the A/C's performance (and even some more involved ones to really get it going).
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Old 07-25-2019, 02:01 PM   #3
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THOR #11726
Quote:
Originally Posted by JamieGeek View Post
You may want to read this lengthy thread:
Try this first before you buy 2nd AC unit or bring your unit in for AC service.

As mentioned in that thread there are a few quick and easy checks you can do to improve the A/C's performance (and even some more involved ones to really get it going).
Thanks for the info. We have sealed any leaky ductwork, and moved the theristor. The only thing we haven't done is insulate the rooftop unit. Can't understand why it worked before and not now.
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Old 07-25-2019, 02:14 PM   #4
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Quote:
Originally Posted by Ladybug View Post
Thanks for the info. We have sealed any leaky ductwork, and moved the theristor. The only thing we haven't done is insulate the rooftop unit. Can't understand why it worked before and not now.
Its probably working as good as it can in the 105 degree heat.

We just returned from a trip to NJ and back. On that trip we camped on asphalt (Liberty Harbor RV park). During the heat of the day (was in the 90s and sunny) our A/C could barely keep up--if the temps in the coach didn't already start relatively cool it wouldn't even start cooling down until 7 or 8 pm at night when the sun stopped being so direct. (We couldn't even extend the awning a little to get some shade: There was an Airstream next to us that was reflecting the sun back on the side of the coach--I'd have to extend the awning over them to reduce that!).

Its pretty much just the heat load: If its super hot outside and you're getting direct sunlight on your coach that A/C unit is going to be working really hard.
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Old 07-25-2019, 02:19 PM   #5
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THOR #13932
Walk over to the rv parked next to you in the rv park tonight.
Ask them if they are having a similar issue.
If that rv is having a similar issue, it's weather related.
Easy.
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Old 07-25-2019, 02:54 PM   #6
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THOR #11130
One A/C unit on a 31 foot anything is borderline in temps nearing mid 90's. During those hottest parts of the day, close off the "unused" end of the coach and open the "dump valves" directly into the area you are using, closing off the ceiling vents in the other area. This all assuming, you only have one A/C.
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Old 07-25-2019, 04:38 PM   #7
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THOR #6903
We have to operate all three AC units when temps get near 100 in order to maintain set point inside around 74 degrees. Any kind of outside shade helps if that is possible and if you get a choice of which direction you park it will help as well.

With 2 inch or so walls none of us have enough insulation for 100 degree temps.
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Old 07-25-2019, 05:07 PM   #8
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THOR #12231
Also use the Refective bubbles in ALL your windows. Its make it dark inside but it will help your RV cool much better.

Or at least use it on the sides with the sun coming in.

It was 95 last weekend and I had the AC set to 72 and it never went off. ONly got down to like 75 - 76 in the RV.

My RV was in full SUN the entire day.

But I didnt put the bubble in all my windows... so on SUNDAY morning I put the bubble in (Before the RV gets hot) and it worked wonders. It was 72 deg pretty quick in the mornig and it held the them all day long and even turned off a few times.
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Old 07-25-2019, 05:23 PM   #9
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THOR #12231
These temps were at the thermostat,

The Cockpit was much warmer until I put the reflective bubbles in place. I have them precut for each window in the RV. When its hot outside and im in full sun I will leave in all the windows (except the Cockpit area when driving).
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Old 07-25-2019, 09:31 PM   #10
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In the thread:

Try this first before you buy 2nd AC unit or bring your unit in for AC service.

You will see about placing a vent on the bottom face of your AC unit blowing into your cab...

This one 8.00 modification has made a world of difference in my VEGAS. On 90+ days now the coach is showing 74-78 degrees where before it was in the upper 80's.. Please don't dismiss this little modification (especially since it only takes a vent and a dremel)..
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Old 07-25-2019, 10:56 PM   #11
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Quote:
Originally Posted by The Gritz Carlton View Post
One A/C unit on a 31 foot anything is borderline in temps nearing mid 90's. During those hottest parts of the day, close off the "unused" end of the coach and open the "dump valves" directly into the area you are using, closing off the ceiling vents in the other area. This all assuming, you only have one A/C.
I totally agree with Gritz ....Thor dropped the ball on units over 31' and full slides ...they should have two ac units ...one unit will not keep up with the amount of square footage once it all opened up...
I ran into the same issue years ago and added the addition unit to my unit.. this was after even doing the bubble wrap in the windows and reconfiguring the air flow on the front unit.....now I have no issues..
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Old 07-25-2019, 11:36 PM   #12
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THOR #1929
I had the same issue. I had my RV tech who I trust and he measured the intake air to the vent air and they should be 20 degrees apart. Mine was 10. I was able to get it replaced by my extended warranty. I up graded from a 13500 btu to a 15000 btu. Last weekend in Florida in full sun I set the temp to 72. Outside air was 95. It kept it cool at 72. I have a 28 foot Class C. Hopefully it will continue. Knock on wood.
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Old 07-27-2019, 03:26 AM   #13
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THOR #14761
Hey ladybug - I have 35 footer sorry not being funny, but I removed the interior roof panels on the Colman AC , 4 screws and found that the AC sensors should be push into the condenser fins . They were both hanging several inches below. Sorry there I go again ,It’s seem to drop about 5 degs colder
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Old 07-27-2019, 01:43 PM   #14
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THOR #12484
As Mo-Mike said, after removing the cover feel the air coming directly out of the blower and compare to what you feel out of the roof vents and that will tell you how well insulated your ducts are. Remember to multiply that difference by the number of vents you have because that is where all that cooler air is going. A vent below the blower was the fix for me, but my unit is only 24 feet. That and turning it into an igloo as LWR describes with the bubbles on the windows keeps me cool.
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Old 07-31-2019, 04:17 AM   #15
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THOR #4243
I have done some of the mods mentioned on my 31L which have helped. Putting a small efficient fan on the floor pointing up a little bit has really helped a lot. Keeps air circulating inside the coach. We usually keep it towards the front of the coach pointing towards the back, helps in keeping the bed room cool.
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Old 07-31-2019, 10:22 AM   #16
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I did all the mods except the round vent but have one on the way. The mods really made a night and day difference but we were in MI and caught a 98* day with high humidity and it took forever to cool it down and then had trouble keeping up. My wife can't take the heat so I am installing a second unit as we speak. I have the wiring mostly done and am installing the unit tomorrow when I will have some help.
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Old 07-31-2019, 03:46 PM   #17
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THOR #2121
Quote:
Originally Posted by Ladybug View Post

......cut.....

Am I just imagining things, or should it at least be keeping it 10-15 degrees cooler than outside? Any help is appreciated!

.....cut......

How cold RV gets relative to outside temperature is a poor indicator of how well your A/C is working (relative to its capacity). I would not go by that because it may just be undersized, yet working perfectly.

A better test is to take temperatures going in and out of A/C inside the motorhome. As discussed in other threads, that will indicate much more information regarding whether youíre getting the full 15,000 BTU/hr of cooling that itís designed to put out.

My technical guess is that one 15,000 BTU/hr A/C is insufficient on a hot day to cool a motorhome that is 32í-7Ē long and has a full wall slide. Thatís roughly twice as large a living area as my previous Class C and it didnít cool great on hot sunny days with one A/C.

Notice in specs that Thor now offers two 11,000 BTU/hr air conditioners for floorplans KW29 and larger. That is almost 50% more cooling than a 15,000 A/C and much more than suggested ďupgradesĒ can provide. Some upgrades that fix problems like leaks are definitely of value, but others that supposedly increase the A/Cís cooling capacity are more questionable as to their magnitude.

Depending on your tolerance to heat and humidity, youíll probably end up needing a second A/C on hot days.
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Old 07-31-2019, 03:52 PM   #18
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THOR #13932
"... Some upgrades that fix problems like leaks are definitely of value, but others that supposedly increase the A/Cís cooling capacity are more questionable as to their magnitude...."

Please specifically name the less than valuable modifications and tell me why they aren't cumulative so I don't do the modifications you question.
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Old 07-31-2019, 05:24 PM   #19
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Please specifically name the less than valuable modifications and tell me why they aren't cumulative so I don't do the modifications you question.
Itís become too personal for some people, so Iím staying out of it. Just use your common sense. As a hypothetical example, if a 15,000 BTU/hr A/C could be easily modified to put out 18,000, why wouldnít the A/C manufacturer do it and sell it as a larger unit? Some of the incremental stuff may help a tiny amount in theory, but I wouldnít waste my time on them. In my experience with refrigeration systems, if its capacity is so inadequate that itís deemed a problem, adding a few percent capacity isnít going to correct the underlying deficiencies.

Just saying that to make a significant improvement, we have to make a significant change. Fixing things that are not working right is one thing (like leaks), but to get more capacity out of given compressor and heat exchangers is a different matter. Some times itís best to accept a large motorhome needs two A/Cs.
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Old 07-31-2019, 07:58 PM   #20
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THOR #16016
its a common problem at AC issue. i'm facing lots for problem at my Toyota car. it can give me satisfaction if i get a complete solution.
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