A little A/C help needed

quicksilvr · Post by **quicksilvr** » Sat Apr 23, 2011 11:45 pm

The A/C in my new 2001 R/T is blowing warm. Normally I'd just take it to a shop, but the more I read and learn about A/C systems, the more I want to make sure I'm taking it to someone who is competent and precise when troubleshooting and fixing A/C issues.

Any one on here know the common causes for an A/C system to get warm on 2nd gen Neons?

Post by **occasional demons** » Sun Apr 24, 2011 12:00 am

Does the compressor run/cycle? If it does, does the cold side get cold, at least enough to get condensation on the lines? If so, the air blend door may not be closing, allowing hot air from the heater core to flow to the vents. If the compressor isn't cycling, or the low pressure tubing isn't getting that cold, it is prolly low on freon. It will need evacuated, recharged, and leak checked, then any leaks repaired to be properly repaired. If it initially begins to get cold, then goes warm, check the condenser/radiator for blockage. Clean any debris if needed. I would think the engine would be overheating if this was the case, but worth looking at if you haven't already.

LilSparkPlug · Post by **LilSparkPlug** » Sun Apr 24, 2011 9:35 am

This may be silly, but is it warm enough outside for the A/C to run? If the car senses a low ambient temperature the A/C will not function. I want to say it's below 50 or 60 degrees but I could be wrong.

Post by **occasional demons** » Sun Apr 24, 2011 7:38 pm

The A/C compressor will still cycle briefly, just as it does with defrost. As long as the temperature/duration of compressor run time is not enough to potentially ice up the evaporator, it will run.

I think it is warm enough there for normal operation. Mine will freeze you out in 40ºF weather if you so desire. It just doesn't need to cycle the compressor as much.

The A/C low pressure switch is electrically connected
in series with the A/C-heater control mode
switch and the A/C high pressure switch, between
ground and the powertrain control module (PCM).
The A/C low pressure switch contact opens or closes
the path the ground, signaling the PCM to turn the
A/C compressor clutch on and off. This regulates the
refrigerant system pressure and controls evaporator
coil temperature. Controlling the evaporator temperature
prevents condensate water on the evaporator
fins from freezing and obstructing air conditioning
system air flow.
On 2.0L LHD models, the A/C low pressure switch
contacts are open when the suction pressure is
approximately 152 kPa (22 psi) or lower. The switch
contacts will close when the suction pressure rises to
approximately 234 to 262 kPa (34 to 38 psi) or above.
Lower ambient temperatures, below approximately
-1° C (30° F), will also cause the A/C low pressure
switch contacts to open. This is due to the pressure/
temperature relationship of the refrigerant in the
system.

Also check the small vacuum line that attaches at the brake booster. It has a check valve in line with it. If that is unplugged, the HVAC controls may not work properly. I think it only operates the recirculate door via vacuum tho. The air blend is moved by a cable attached to the temp knob.

quicksilvr · Post by **quicksilvr** » Mon Apr 25, 2011 12:30 am

Thanks guys. The car is still in Phoenix, but I'm getting it next week. Fixing the A/C is pretty high on the list of stuff to do right away.

I'll use this info to troubleshoot it myself a little, so I'm educated as to what is going on before I take it somewhere.