Dash air in 90 Deg heat.

[BigLar368]

I did A/C work for 12 years as part of a time in my life as a heavy equipment mechanic. Never formally trained but taught myself enough to know right from wrong. Our RV dash A/C blows fairly cool but not cold. If we just use the dash A/C on max for a few miles it does blow pretty cool but never cold if it's hot outside. I know when we stop the RV water/condensation pours off the suction lines which are ice cold. The problem is the return air coming from the RV can not be cooled enough to over come the heat load which is constantly getting into the RV through the HUGE windshield and other places that are not sealed up. The A/C will never cool the air enough to comfortably drop the temp of the RV. The A/C compressor on our RV is no bigger than one you would find on a passenger car.

Now some of you may have a dash A/C that blows super cold.....Maybe your RV is sealed up a bit better. For our dash air to blow cold we have to start the living room A/C (On genny power) and after about 15 mins or so the front dash A/C is blowing so cold it's uncomfortable. This is due to the return air being cooled with the help of the roof A/C. Cooling off a passenger car with the same sized compressor as an RV is much different than trying to cool off and RV with the same size compressor as a passenger car. Just my opinion.

[hotdog2]

Yes thank you REACHER he did say it was contaminated refrigerant. I took that as dirty gas. Sorry for the grammatical miscommunication.

[Reacher]

Originally Posted by BigLar368

I did A/C work for 12 years as part of a time in my life as a heavy equipment mechanic. Never formally trained but taught myself enough to know right from wrong. Our RV dash A/C blows fairly cool but not cold. If we just use the dash A/C on max for a few miles it does blow pretty cool but never cold if it's hot outside. I know when we stop the RV water/condensation pours off the suction lines which are ice cold. The problem is the return air coming from the RV can not be cooled enough to over come the heat load which is constantly getting into the RV through the HUGE windshield and other places that are not sealed up. The A/C will never cool the air enough to comfortably drop the temp of the RV. The A/C compressor on our RV is no bigger than one you would find on a passenger car.

Now some of you may have a dash A/C that blows super cold.....Maybe your RV is sealed up a bit better. For our dash air to blow cold we have to start the living room A/C (On genny power) and after about 15 mins or so the front dash A/C is blowing so cold it's uncomfortable. This is due to the return air being cooled with the help of the roof A/C. Cooling off a passenger car with the same sized compressor as an RV is much different than trying to cool off and RV with the same size compressor as a passenger car. Just my opinion.

Very true BigLar. As an alternative when it's really hot out we rig a couple of clear shower curtains with velcro and seal up the cockpit. The dash a/c works great then!

[leadman]

One big problem with RV dash air conditioners is the fact that most could be getting heat from the engine thru the heater valve in the blend air box.
This is not too hard to check. Locate the 2 heater hoses that are at the blend air box. With the engine warmed up and the a/c on these should be ambient temperature. If not the control valve that is in the heater hose is either bad or if cable operated out of adjustment.
If no in line valve then it is possible the door in the blend air box is not closing.
If your a/c control is the Ford type with the vacuum lines coming out of it make sure it functioning correctly. The lines can leak or be pulled loose or the control itself may be leaking vacuum. If the GM style that has a cable to the in line water valve make sure it moves enough to shut off the flow of hot water.
I put a couple of in line valves in our old MH, a 1987 Itasca. The current owner, my neighbor put a manual shut off in the line because the in line valve is bad again.
On our current '99 Winnie with Ford chassis I had to use a hand held vacuum pump and check the vacuum lines in the dash, firewall, on the engine, and by the right front tire for leaks. I found many and also had to replace the dash control valve.
On some units you can put a temperature gauge in the evaporator and disconnect the blower to see if the evaporator is getting cold with no air flow over it. Should get down to 35 degrees to 50 degrees, depending on the thermostat. Colder than 35 is not good as this will cause the evap to ice up.
Warmer than 50 and it will not cool good with the fan on.
Air intrusion thru the firewall, etc. can be plugged up and does help a lot in how well the a/c cools.