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07-21-2022, 08:49 PM
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#1
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3401
State: Texas
Posts: 122
THOR #25110
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AC doesn't cool at freeway speeds
The shop that works on my cars agreed to look at the dash AC on my 3401 today. I had put too much freon in it so he got the charge right. Parked and running at fast idle it was about 40 degrees discharge temperature at the center duct. I test drove it about 10 miles on the freeway and the outlet temperature slowly went up to 60 degrees. When I slowed down and stayed on the frontage roads going back the temp started going back down. Again parked with the engine on fast idle it dropped to the low 40's.
Any idea what could cause this. He ran it at 1500 RPM when I got which is about the engine speed on the freeway and it cooled OK. (I'd live 35-38 degrees like my car but I can live with 40-42).
Thanks
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07-21-2022, 11:58 PM
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#2
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Senior Member
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 1,410
THOR #2631
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Just a WAG here. I think vacuum decreases with engine loading so perhaps when you are loading the engine actually driving on the freeway (especially going up a hill) vs sitting in your driveway, the engine vacuum drops and that may be enough to affect the vacuum operated blend door in your dash A/C unit (or a vacuum motor, etc.). Maybe a deteriorating or leaking vacuum hose connection somewhere or leaking vacuum check valve. If the hill is a long one you might experience a temp shift in the coach depending on outside air temp etc. I would also expect coasting down hill (throttle body closed) would raise engine vacuum and cooling would return to "normal" if there were no leaks. Not sure if there is a vacuum reservoir on these coaches.
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07-22-2022, 12:14 AM
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#3
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3401
State: Texas
Posts: 122
THOR #25110
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I’m not sure what operates the doors on this AC because the engine is diesel so there’s no engine vacuum. The fresh air doors are right on the front of the evaporator and I have thought about taping them closed.
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07-22-2022, 12:28 AM
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#4
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Senior Member
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 1,410
THOR #2631
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Guess I should have looked a little closer at your coach info. A vacuum pump on the diesel maybe? Sorry not familiar with your dash A/C controls either so I will bow out for those that would know your coach details better than this gasser does.
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07-22-2022, 12:42 AM
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#5
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Site Team
Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,129
THOR #7035
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Was this on recirculate? I would imagine a fresh air mix at 90+ degrees at highway speeds could dilute that cooled air.
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Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad - Selling
2020 Chevy Colorado Z71 Trail Runner Toad
2024 Chevrolet Trax 2RS - Soon 2B TOAD
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07-22-2022, 01:30 AM
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#6
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3401
State: Texas
Posts: 122
THOR #25110
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Yes. I keep it on recirculating
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07-22-2022, 01:55 AM
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#7
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Senior Member
Brand: Thor Motor Coach
Model: 2020 Magnitude SV34
State: Florida
Posts: 4,147
THOR #12751
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It almost sounds like the compressor is turning off when the engine is under load. I can remember some A/C’s doing this to conserve fuel back in the day.
I seriously doubt that is what’s happening but there may be a relay that is only intermittently working and causing the compressor to turn off randomly at times.
I have a 2002 Lexus that started doing this a couple years ago. After doing some online reading and troubleshooting it turned out to be a bad relay. I picked one up at the auto parts store for $20 and replaced it. It has been working fine ever since.
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07-22-2022, 03:33 AM
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#8
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3901
State: Idaho
Posts: 695
THOR #9660
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I have noticed the same thing at speed in our 3901. But I have found that it works fine when the fan is on the fastest 2 speeds. Ours also works at all speeds on recirc. I think it is air pressure in the generator compartment closing the intake door when not on recirculate, but not absolutely positive.
Mike
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Vicki and Mike, Aria 3901- The Wined Up Bus, towing 16 Jeep JKUR.
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07-22-2022, 10:40 AM
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#9
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Quote:
Originally Posted by ChiefBob
I’m not sure what operates the doors on this AC because the engine is diesel so there’s no engine vacuum. The fresh air doors are right on the front of the evaporator and I have thought about taping them closed.
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My Coach uses a vacuum pump for the controls
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07-22-2022, 04:09 PM
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#10
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Junior Member
Brand: Thor Motor Coach
Model: Challenger 37LX
State: Virginia
Posts: 29
THOR #26801
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My first thought was at highway speeds the pressure might be getting too high which would cause the compressor to shut off unit the pressure is reduced which could be 5-10 seconds later and then the compressor is back on, then back off..... I'm no HVAC mechanic but my understanding of the AC system thinks this is possible.
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Rob
Virginia Beach, Va
2015 THOR Challenger LX
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07-22-2022, 08:56 PM
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#11
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Senior Member
Brand: Thor Motor Coach
Model: Challenger
State: Maryland
Posts: 108
THOR #25281
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Quote:
Originally Posted by ChiefBob
The shop that works on my cars agreed to look at the dash AC on my 3401 today. I had put too much freon in it so he got the charge right. Parked and running at fast idle it was about 40 degrees discharge temperature at the center duct. I test drove it about 10 miles on the freeway and the outlet temperature slowly went up to 60 degrees. When I slowed down and stayed on the frontage roads going back the temp started going back down. Again parked with the engine on fast idle it dropped to the low 40's.
Any idea what could cause this. He ran it at 1500 RPM when I got which is about the engine speed on the freeway and it cooled OK. (I'd live 35-38 degrees like my car but I can live with 40-42).
Thanks
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Hello sir and sorry for your troubles. If the a/c is operating properly at idle I would look at the fan clutch as there could be a problem with the clutch controlling the fan. Not really familar with your set up but if it's running good at idle and your driving down the road and it warms up and your mechanic is sure they have the charge right then I would look at the fan control that sucks air thru the condensor. It is either electrically controlled or hydraulic, and should be 2 speed control for just this purpose. Car a/c and diesel pushers are two totally different things. Especially when talking about a/c. Also keep in mind that if the freon charge is off there are sensors installed in the system that will shut the compressor off if it exceeds or drops below minimum pressures. Obviosly there is a leak in the system as with most diesel pushers because there are a lot of lines that could potentially leak and the fact that you had stated you over filled the system. Take it to a proffesional who deals with diesel pushers and I'm sure they will find the issue. I always measure the amount of freon I add by using scales to prevent over charging. Good luck and hope this may help some
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07-22-2022, 09:49 PM
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#12
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3401
State: Texas
Posts: 122
THOR #25110
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Thanks. I wish I could find a place that is good with diesel pusher AC. I would gladly pay to have it work right.
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07-23-2022, 03:29 PM
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#13
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany
State: Texas
Posts: 480
THOR #1808
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i run my dash air at the MAX setting to prevent the circulation vent form opening. that alone will keep temps cooler at the center
i would also look at the electric fan on the condenser up front on one side of the generator and see if it cycles on and off as needed when you are running at fast idle to test system
i would add ...my tuscany dash air has been a pita since new
new everything, and it will charge and be freezing cold air and then 2 weeks later losses enough freon to stop working. i have vac and pressure checked for 24 hrs at a time and it is leak free. but then it looses charge.
our chassis take a lot of freon to work. its nearly 80 feet of hose .
you can also under the front hood tape over the fresh air damper and it will not allow any outside air in. dont know why they build them that way, its a big hole for dirt and stuff.
its all basic stuff under there, any good ac shop should be able to look at it.
the compressor on the engine is a bit tricky to remove but its easy to find for replacement.
your engine should not be cutting off compressor at highway speeds, if it is..it most likely low on charge and not cuttign off, but not having enough refrigerant to pump up
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retired Navy driving the short bus 2008 Tuscany 4056
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07-23-2022, 04:01 PM
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#14
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Quote:
Originally Posted by powerboatr
i run my dash air at the MAX setting to prevent the circulation vent form opening. that alone will keep temps cooler at the center
i would also look at the electric fan on the condenser up front on one side of the generator and see if it cycles on and off as needed when you are running at fast idle to test system
i would add ...my tuscany dash air has been a pita since new
new everything, and it will charge and be freezing cold air and then 2 weeks later losses enough freon to stop working. i have vac and pressure checked for 24 hrs at a time and it is leak free. but then it looses charge.
our chassis take a lot of freon to work. its nearly 80 feet of hose .
you can also under the front hood tape over the fresh air damper and it will not allow any outside air in. dont know why they build them that way, its a big hole for dirt and stuff.
its all basic stuff under there, any good ac shop should be able to look at it.
the compressor on the engine is a bit tricky to remove but its easy to find for replacement.
your engine should not be cutting off compressor at highway speeds, if it is..it most likely low on charge and not cuttign off, but not having enough refrigerant to pump up
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Luckily, I have never had to add freon nor have had any issues at all, and it produces very cold air. I always push the recirculation button, so it is lit up and that keeps the outside air vent from opening. Then we tend to run on the third speed to keep the fan noise down a bit.
Keeping the outside air vent is important and checking to be sure no hot water is leaking through the closed heat valve is important as well. That could be an issue with higher speed warming or failing to cool.
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07-23-2022, 06:41 PM
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#15
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Senior Member
Brand: Thor Motor Coach
Model: Aria 3401
State: Texas
Posts: 122
THOR #25110
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Thanks all. I had my very good AC man get the charge right but his expertise is cars so admits he is at a loss on this scenario. He wonders if the condenser in the front is not getting good air flow when driving at higher speeds. I thought about fabricating some sort of air scoop on the bottom to direct air up there.
I don't know how to determine is the compressor is cycling off at high speeds. When parked and the RPMs set around 1500 is still seems to cool OK, although I would really like lower than 40 degrees.
The AC components are made by Comfort Aire so I plan to call them next week and see what they say. My questions to Thor were answered with "call Comfort Aire.
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07-23-2022, 09:30 PM
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#16
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany
State: Texas
Posts: 480
THOR #1808
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Quote:
Originally Posted by ChiefBob
Thanks all. I had my very good AC man get the charge right but his expertise is cars so admits he is at a loss on this scenario. He wonders if the condenser in the front is not getting good air flow when driving at higher speeds. I thought about fabricating some sort of air scoop on the bottom to direct air up there.
I don't know how to determine is the compressor is cycling off at high speeds. When parked and the RPMs set around 1500 is still seems to cool OK, although I would really like lower than 40 degrees.
The AC components are made by Comfort Aire so I plan to call them next week and see what they say. My questions to Thor were answered with "call Comfort Aire.
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your condenser should have a BIG electric fan on it, road speed is not dependent on proper working order
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retired Navy driving the short bus 2008 Tuscany 4056
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07-23-2022, 11:33 PM
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#17
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Mine is like that
Maybe a relay or power issue but exactly, should run if on
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07-24-2022, 12:04 AM
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#18
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Senior Member
Brand: Thor Motor Coach
Model: Thor Ace 33.1
State: Illinois
Posts: 1,266
THOR #20274
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When a person is driving at highway speeds the fan isn't necessary
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07-24-2022, 12:04 PM
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#19
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Senior Member
Brand: Thor Motor Coach
Model: Tuscany 42GX
State: Missouri
Posts: 1,158
THOR #9178
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Quote:
Originally Posted by Bill Johnson
When a person is driving at highway speeds the fan isn't necessary
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So, is there a pressure or temperature sensor?
Will look at mine closer
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07-24-2022, 12:15 PM
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#20
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Senior Member
Brand: Thor Motor Coach
Model: Thor Ace 33.1
State: Illinois
Posts: 1,266
THOR #20274
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Quote:
Originally Posted by lwmcguir
So, is there a pressure or temperature sensor?
Will look at mine closer
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Most vehicles ac fans turn on when the ac is turned on, only the engine fans an cars usually turn on by temperature. I was just saying the amount of air going through the condenser at highway speeds should be adequate
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