A/C Mystery... help

[wethepplebmxer]

ok... I'll start with the basics...

97 GTP... single zone climate control.

A/C isn't working... Blows hot air on driver and passenger sides.

Had the A/C charged at the shop earlier this summer... this resulted in "cool" not cold air blowing in from mostly the passenger side. Air was never up to par with where it should be. within a couple weeks the cool air was gone.

Things I've checked:

A/C unit is turning on... also the A/C clutch is functioning.

The system does have freon (sp?) in it...


What am I missing here...?

[Airjer_]

Sounds like it is low on charge because of a leak? What are your pressures at? did the shop put dy in the system?

[CrazyHorst]

Easy thing to do is to check and make sure the AC condensor is not plugged with junk. This would prevent heat transfer to outside air. Also check to make sure the general condition is good. High speed driving in salt/snow/gravel environments can fold over the lower fins and hint at other potential "wear" problems. I would hesitate to use any water-pressure washing device but I would use compressed air regulated to 60 psi or so if you are prudent with the application.

Next, you could be plugged internally if there was a high level of (usually aluminum debris) present at assembly. That would probably mean orifice tube to me, and I'd strongly consider a compressor change if you are running the original after 6 figures of accumulated mileage.

[doctorhrdware]

Even at 60psi the posibility to bend the fins is great. I would use a tooth brush to remove the surface crud from the condenser fins. Then use like a strip of plastic to get the crud that is in the middle of the condenser.

[wethepplebmxer]

is the condenser easy to get to? and how hard would it be to swap out?

[Airjer_]

The condenser is in front of the radiator.

[BNaylor]

What were the low side and high refrigerant pressure readings? Running A/C manifold pressure gauges can tell alot and which direction to go or most likely what components without speculating or wasting money on parts that may be OK.

Make sure you have at least 2.25 lbs or 36 ounces of R134a refrigerant. GM upped the figures so the old data on the labels is probably incorrect.

[bmwdriver2009]

#1 make sure auxillary fan is working,electric fans in front ,behind radiator,should work with ac on,both fans
#2 heater control valve or hot water valve bad,stuck in the open position allowing water ,aka hot coolant into evaporator area making cool air hot
#3 ac low on charge or over charged ,ac will blow out warm air if overcharged
i have a 2001 grandprix gtp special edition 2 door coupe and i am a bmw tech as well

[BNaylor]

Originally Posted by bmwdriver2009

#2 heater control valve or hot water valve bad,stuck in the open position allowing water ,aka hot coolant into evaporator area making cool air hot

Good overall advice bimmerdriver however the heater core has constant flow in and out as far as coolant pressure and return as long as the engine is running and the water pump is pumping and thermostat is open. There is no separate heater control valve for the heater core. The temperature actuators control the blend doors and mix between hot and cold in the lower HVAC assembly via the climate control unit.

[richtazz]

Another question, did the shop draw the system down before recharging or just add refrigerant? Drawing the system down pulls all the old refrigerant and mositure out, creates a negative pressure which helps the system accept the new regrigerant better and also will show any leaks (as the system will not hold vacuum if a leak is present). If the shop that recharged it didn't do the job correctly, we could guess all day as to what the current problem is. As Bob stated, as set of proper guages capable of reading both high and low system pressure is a necessity for accurate diagnosis.