Dash AC Question

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ELeland

Well-known member
Joined
Dec 21, 2017
Posts
211
Location
Jupiter, FL
I recently had the dash AC recharged and had a question.  When I first start the motorhome, the AC blows really cold (44 deg. with IR gun with outside temp in mid 80's).  After about 30 minutes on the road it eventually stops blowing cold and is more like room temp.  Is it over charged and freezing up?  That cold air up front sure is nice on hot Florida days even with the rooftop AC's on.

Any help or suggestions are appreciated.

Thanks

Ed
 
This happens every time you drive, or was it just once after the recharge?  Is it the same whether the system control is set to Max (Recirculate) vs normal a/c?

If every time, I would suspect some component in the a/c system, or maybe the surrounding heat just builds up enough after 30 minutes to overwhelm the a/c system. Somebody with more a/c smarts than I can maybe tell you how to determine whether the a/c itself is not chilling vs the chilled air getting mixed with too much hot exterior air.
 
    The worst money I spent on the MH was repairing and charging the dash air.  With the engine in the rear, the A/C condenser up front, it never did seem to operate properly, plus it is overwhelmed by trying to cool the whole coach.  Also, in the humid air of Florida there likely is a fair amount of icing on the condenser.
    On hot days while travelling we ran the generator and the roof air.

Ed
 
It possibly could be a blend actuator door that electronically opens and lets fresh air or heat in.  Do you ever hear mysterious clicking sounds under the dash?  After it seems to get warm, try changing positions on dash . defrost etc.  Also try changing temperature gauge.  Also as you suggested, it could be slightly overcharged, but that rig, I'd let the guy that recharged the AC evaluate it with good gauges.
 
This could be a number of things, over charged, bad expansion valve, clogged condenser, ... It really is hard to tell without gauge readings.
 
When it stops working you could pull over and see if the compressor clutch is engaged. If it is then find the A/C lines, the bigger one should be cool/cold to the touch and the smaller one should be warm. If so then the compressor is probably working adequately unless the belt is slipping at higher speed.

If all appears good then move on to the blender door and make sure it is set so that no air from the heater side goes into the cold air. This door can be electric or vacuum operated

While stopped place the heater control to full heat and leave it there for a while with the heat blowing out full blast. does a lot of water start running out of the coach (some is normal)near the cooling coil? If so the coil may be  freezing and A safety may be shutting off the A/C.
 
I've used it several times since the repair and had the same result whether on recirc (max AC), just AC or defrost.  All kinds of noises in a MH but couldn't differentiate if they were related to the AC.  Shutting down the AC or changing settings didn't change the noises.

I think SpencerPJ nailed it - take it back to the tech that repaired it. 

I'll let you know what he finds.

Ed
 
There are multiple causes of that (As the engine heats the A/C "Stopps" workign

1: AC condenser fan relay not working fans not kicking in and cooling condenser/Radiator
2: Engine heat being radiated into condenser
3: If you have a flow-control heater the water valve is not closing properly so the heater is kicking in.. If it is an air-flow type. the flapper door is stuck.

Take your pick. 3 is most common and my pick.
 
Since you say it starts off cooling good, then later quits, makes me wonder if it being shut off with a freeze or temperature switch (takes the place of low pressure switch) on or near the evaporator coil. In a case like this it probably won't start cooling again until this switch warms up enough to restart the compressor.

Could possibly be any other component failing after running a while. High pressure switch tripping or bad. Condenser fans not working properly. Dirty condenser coil. ETC
 
Neal said:
Since you say it starts off cooling good, then later quits, makes me wonder if it being shut off with a freeze or temperature switch (takes the place of low pressure switch) on or near the evaporator coil. In a case like this it probably won't start cooling again until this switch warms up enough to restart the compressor.

Could possibly be any other component failing after running a while. High pressure switch tripping or bad. Condenser fans not working properly. Dirty condenser coil. ETC

It took 2 years to find it but the evaporator temp switch failed.  The behavior was similar to the OP's question.  It interrupts the clutch on the A/C compressor when it gets too cold.  Of course replacing it is a ton of work so I plugged in a fuze to short it out or keep it off electrically.  Now the A/C works great as long as the humidity does not get too high.  If the coils ice-up just turn off the A/C for a few minutes and the ice will melt and then you go back to cool.  Worth a try to see if that's the issue... You know the compressor is working since it cools initially so something is turning the compressor off.
 

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