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Old 10-20-2014, 10:23 AM   #1
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What else impacts dash A/C besides heater core?

Like most people in areas like Florida & South Texas, we usually run our house A/C while traveling during summer months to keep the coach cool. However, recently I noticed that he dash A/C had started to blow hot air when in use.

Took it into Freightliner in Houston and they did a refrigerant recovery and then refilled to the 2.5 lbs that is indicated on the sticker. The tech let it sit at fast idle for an hour and confirmed that it was cooling to around 60 in 85 weather. As soon as I got on the freeway driving home, it was blowing hot again. But as soon as I got to a stop light, it cooled right down.

I have reviewed all the posts started by RedBaron73 and the Evans valve is definitely installed on the wrong hose and is failing. Nemar has offered a discount on the part but will not replace it even though it was their mistake, it is out of warranty and I am not the original owner. I will replace it, however, that is not the real problem.

Understanding that the valve issue exists, I crimped off both sides of the engine coolant lines to the heater core. And then ran some tests that confirmed it isn't cooling correctly at higher RPMs but then discovered that it may not be A/C related. When on vent only, the same issue occurs and the heater core can't be the issue. Attached is a chart of what the tests looked like. These were taken while sitting still and the incoming temp remained constant at the fresh air inlet on the Evans unit.

So my question is, what else could be causing an increase in temperature as the engine rpm's increase. The engine temp doesn't change. The only thing that came to mind is could the water recirculation from the Oasis system to the house heating vent in the dash be causing this? You guys are way smarter than I am, any thoughts?

Thanks.
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Old 10-20-2014, 04:33 PM   #2
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Not sure you have read through this PDF by Evans, why you have the heat build up with heater hoses clamped to block heated water from heating the AC/Heater core is a good question do not see how with this PDF information.
Other Evans info in QT's 1 & 2.
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Old 10-20-2014, 05:50 PM   #3
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some ac units have a door that swings to block off the heater core some of these are move by vacuum others by electric motor( it is what is hooked to the lever you move or dial that changes setting) you will have either a electric pump or it will come off your engine if it is a gasser. even if it just move a little it mixes the cool air with warm /hot air causing the temp diff you feel
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Old 10-20-2014, 09:23 PM   #4
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The Evans control valve is what shuts off the heater hot line into the AC/Heater coil unit.
Some Evans controls were installed incorrectly and because of this the water flow went into it and reverse causing the control to break down thus becoming defective.
The OP is aware of this and says he has another problem with hot water coming from another source.
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Old 10-20-2014, 09:36 PM   #5
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You may have a blockage in the suction line from evap to compressor. Run ac when engine is at fast idle and outlet temps start to rise. Follow line and look for frost buildup on line. Rubber hoses may take some time to frost up. You also may have an over service issue and I would have another ac tech check pressures and temps. Also check condenser fan if your condenser is mounted under front of mh.
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Old 10-21-2014, 10:12 AM   #6
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Thanks for the responses so far. "007" I had read a part of .pdf you referenced but the link you provided supplied more info than the one I had looked at previously.

Stink, I won't have the MH at the house until Thurs. will check it out.

Still struggling with fact that the temp rises on vent setting at higher RPMs. Can an issue with the AC system actually heat up the evaporator?
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Old 10-21-2014, 12:16 PM   #7
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Dave above mentioned a possibility, but your condenser is back at engine location though, I supplied the link for you to see the hosing for hot water and AC Freon connections in case some thing is wrong with them, I drought it though.
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Old 10-22-2014, 08:15 AM   #8
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Check the vacuum hose as your engine rpms go up vacuum drops this will mix air inside plemun and cause the temp rise when under power when the vacuum returns the door closes and the temps drop. it does this on vent or a/c .
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Old 10-23-2014, 06:16 PM   #9
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dash air

I have a problem with the dash air on my 2012 ventana. I took it to a service center that sells Newmar motorcoaches. They told me that there was nothing wrong with the a/c. I knew better, having worked in the automotive industry all of my life. The service tech told me to take the coach to Freightliner because the fault had to be Freightliners and not that of Newmar. The coach was still under warranty so I did as they requested. The Freightliner dealer gave me an appointment and that it would not take long to check it out. After several days (8) they called and said that the coach was ready. Upon arriving at the service department they informed me that I owed them $445.00. I was shocked, I said that this was supposed to be covered by my warranty. I refused to pay, (I have bought many propane trucks from this dealership. They allowed me to sign the invoice in protest and leave with the coach. This was at 9:45 pm and I live almost two away from the dealership. I was so mad I forgot to check the operation of the a/c. Turned it on and you cussed it , nothing had changed at all. Then the a/c is set to the coldest setting there was no problem only when you went to raise the temperature a degree (1) the system went into heater mode. As you have guessed I now have spent a lot of time and money and nothing has changed. Ice cold air or heat nothing in between. I called freightliner in Greenville SC, they told me that the a/c unit was not a Freightliner installed part and that it was installed by Newmar Corp. Back to the service center (the one closest to my home, 30 miles away) I had them to call Freightliner and hear from them that the problem was the a/c unit and not that of Freightliner. The Evans water control is defective but because the service has decided that he can not be wrong, I get along detailed print out of a lot of nonsense. After all this I still have an a/c unit that does not work as it should. I will have to order the new and improved Evans water control valve with wiring harness and fix it myself. The sad part is after all this, I am going to have to fix it myself, so much for a warranty. I suggest that maybe you should try a new water control valve also.
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Old 10-23-2014, 10:15 PM   #10
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Quote:
Originally Posted by johnnysfun View Post
Thanks for the responses so far. "007" I had read a part of .pdf you referenced but the link you provided supplied more info than the one I had looked at previously.

Stink, I won't have the MH at the house until Thurs. will check it out.

Still struggling with fact that the temp rises on vent setting at higher RPMs. Can an issue with the AC system actually heat up the evaporator?
If there is a restriction in the suction line you get two "expansion valves". One at the evap and one at the restriction. An expansion valve is no more than a restriction that causes a lowering of pressure thereby lowering the boiling point of the freon. As the engine rpm goes up the compressor speeds up and pumps more freon. This extra freon settles in the lower part of the condenser and the dryer. With a restriction in the suction line the extra is now stored in the evap. The heat you feel is leftover heat from the condenser and the heat of compression from the compressor. Feel the cylinder head of a running air compressor and it will be hot from the heat of compression. As I said, run engine at fast idle and look for frost and feel for a temp drop in the suction line. If the liquid (small) line to the evap is plugged you would not get any cooling at all. Hope this helps.
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Old 10-24-2014, 02:38 PM   #11
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jdougles welcome to the forum and irv2.
If you read this link you may find out why your Evans AC/Heater is not cooling correctly, the control valve maybe installed wrong, this has been a problem since I have owned a coach and its happening on SOB's.
In my signature below are links to many others that apply to your coach.
Enjoy the forum and safe travels.
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Old 10-27-2014, 05:42 PM   #12
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Thanks for all the suggestions. Stink, I checked for condensation on all the hoses and really didn't find any "hot" spots or in this case, cold spots.. I think at this point, I will go ahead and replace the valve since I know that needs to be done anyway. Then when the weather warms up again, I will get back to troubleshooting any other issues.

Thanks again for all the suggestions.
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Old 11-12-2014, 02:27 PM   #13
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Seems to be working correctly now

Good news on the Evans valve replacement. But first the embarrassing part, when I went to remove the outlet hose from the inlet port on the valve, coolant started spraying out even though I had it clamped like I did during testing. Even though the hose was flattened (and I thought tight) water was still able to get past the crimp. So that left the possibility that hot water was still getting to the heater core as engine rpm's increased.

So after installing the new valve and re-plumbing the hoses so that the inlet hose actually went to the inlet valve, everything seems to work as it should. Engine rpm's don't affect cooling temps and we are once again getting consistently cool air when on AC. Of course, it was in the 70's when I tested it but I was getting almost a 30 degree drop in AC air temp vs outside air. Guess we will see when we get back to those 90 temps next summer.

Thanks to everyone for the great suggestions.
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Old 11-12-2014, 07:45 PM   #14
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Good to hear all is well, might have opened the radiator cap to release pressure you just need to add coolant.
As long as the valve is installed in correct input to core your all set.
This problem has been around for a long time and people would install new valve same location only to have it fail again, not realizing its in the wrong inlet.
Stay cool we maybe sending some cooler weather this week, in that case be warm.
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