A/C woes: compressor working, system full, so why no cold air?

[feddomw]

Anyone have any thoughts? As described, the mag-clutch engages, the compressor kicks in, no error code or blinking A/C light on the climate control screen (I have the facelift 100 with satnav), no bubbles in the sight glass so I will assume the system is still correctly filled, my center console fridge is cold (this last thing will have many US people puzzled I bet), but the a/c will not blow cold air. The air is marginally cooler than the outside temp, but as cold as it should be.

The reason I mention the fridge is that the service specs for filling the system differentiate the total fill weight for with/without fridge, so the fridge must be cooled by the a/c system. Thus, if the fridge is cold, why won't the other vents blow cold air?

 

[AMGAndrew]

Put a set of ac gauges on it or take it to a garage and have them do it. I'm guessing it's low on freon but has just enough for the compressor to engage and cool the fridge but not enough to cool the cabin hvca. Or the compressor is getting weak and can't pressurize the freon enough. Either way, gotta get gauges on it to know for sure.

 

[Julian Stead]

Possible temp control flap issue inside the heater box, does it work in manual or auto at all..

 

[BrandonAz]

The sight glass isn't very accurate for determining the amount of freon. You really need to check it with gauges. I'd start there but I'm guessing the issue isn't freon related. It's probably in the controls or a blend door issue.

 

[feddomw]

Thanks for the input thusfar.

I guess I am looking for that "magic bullet" test I can do to single out the fault or broken part, that we often see here in 'Mud. I will go to a specialist, but I like to have some sort of "google diagnosis" beforehand. It's my process, don't knock it....

My gut feeling was freon too, but because the fridge works, I did some more investigating.

Possible temp control flap issue inside the heater box, does it work in manual or auto at all..

I don't really understand the question. I only have an auto setting: you set the temp and the system cools to that temp. Lowering the temp so the system blows cooler for example, does not lower the output temp. When turning off auto I essentially override all setting for the system, which vents, fan speed, etc. Changing the temp or vents does not change output temp right now.

The sight glass isn't very accurate for determining the amount of freon. You really need to check it with gauges. I'd start there but I'm guessing the issue isn't freon related. It's probably in the controls or a blend door issue.

Blend door is some valve on the output side of the hvac that adds ambient temp air to whatever is coming out of the hvac to create a requested temp airflow? Chekc with guages is not DIY. When they check it with guages, are they checking temps or actual pressure in the AC system? This varies widely during the cooling progress no?

 

[Ninja Cruiser100]

Why so combative? Get a set of HF gauges and learn how to use them...it is really quite easy.

 

[LBridges]

...
Blend door is some valve on the output side of the hvac that adds ambient temp air to whatever is coming out of the hvac to create a requested temp airflow? Chekc with guages is not DIY. When they check it with guages, are they checking temps or actual pressure in the AC system? This varies widely during the cooling progress no?

The system sends hot water through the heater core all the time - the blend door blends the hot air moving through the heater core with with the cold air moving through the evaporator. If the door is stuck it could be sending too much heat through - so there could be nothing "wrong" with the A/C side of the problem.

Gauges at Harbor Freight are about $60 and they check high/low (liquid/vapor) side pressures. The pressure readings you would get from a set you bought yourself are the same things an A/C tech would get - and a pressure check is likely to be the first check performed at a shop.

Didn't say if you have rear A/C, but after the compressor each system is separate - so it could be things like a bad expansion valve in the unit in the dash, etc. Gauges help significantly in narrowing down the problem. The FSM (at least for my 2000 LX) has pages devoted to the readings.

 

[Jimthom]

If you decrease the Set Temp, in Auto mode, to the minimum, it will say Min ( or something like that, LC not with me today). In this setting it blows cold air all the time, no matter what the inside temperature is. There is no hot air mix. This would still not be able to distinguish between weak cooling or a stuck blend door, IMHO. But it might help in your diagnosis.

 

[BrandonAz]

It's also not so much about just being able to check the high and low side pressures with some gauges but understanding where they need to be and what it might mean if they aren't correct.

 

[ibrahim83]

my bet is on the blend door. especially with a cold fridge. Had the issue with my bmw, the valve was stuck and i was getting warmer than normal temps.

 

[vipergrhd]

Just get some gauges hooked up and go from there, it's always easy to replace when you know what is broken or inop. Your expansion valve could be stuck close too. Just my 2 pennies.

 

[TheForger]

I would definitely check with gauges first. I did have the servo motor that operates the blender door crap out on me about a year ago. Got it diagnosed and replaced at a local shop. I believe the pn is 87106-60120 but please double check that.

 

[re_guderian]

Can you add refrigerant yourself in Europe? If so, it's easy to over fill, which is equally bad. There is no substitute for hooking up a set of gauges to both the high and low side and getting a reading at high rpm's and known ambient temps. The process is detailed in the FSM as well as the acceptable ranges, and possible root causes for out of range readings.

 

[PADDO]

Until you can get some gauges thrown on and your suction/discharge pressures read under test loading you might try putting the AC into self test mode and see if any DTCs are thrown - I'd be looking for a 31, 32, 37, 41, 42 code related to the front air mix damper servo circuit.
If you've an 05 with nav then:
Hold AUTO and REC buttons in and turn IG on and the system will do its indicator check followed by a DTC Sensor check. Any codes displayed where the time is normally shown? Now push the REC button to enter the Actuator check mode and see if something is displayed. If your damper mixer (blend door) cct is faulty you might get a DTC or two.