Hi guys,

I have a 04 TL and it's been great for the past 3 years. Few days ago my AC started acting a bit strange where the compressor seems to disengage when I'm sitting at a traffic light and the air coming out would get gradually hotter. Once I get moving again everything would be back to normal.
The situation is however getting worse where the compressor would seemingly stop running even as I'm driving highway speeds. I don't think it's a coolant issue since when the compressor does decide to engage, it does cool well. Also this seems to be related to car temp as when the car is cool in the morning things seems to work.

Any ideas? I've searched but most results are about the AC not being cool and a coolant issue.

 

Can anyone help?

 

Thanks LoveMyTL-S!

Just a bit more info everyone - from Sunday and Monday, the A/C seems to only run when the engine is starting from a cold start. In fact it works pretty well during that period and performance seems to deteriorate with increase in engine temp and finally loss of all cooling when engine reaches equilibrium (temperature gauge just below half way). I've also checked the refrigerant delivery pipe and it does get cold during the initial cooling, but not freezing as I've read about. One engine heats up this pipe returns to normal temp and of course I have no cool air.
I worked on it with my dad last night and we have 2 theories:
1) The drive belt is aged and increased heat is causing it to expand more and the compressor pulley is slipping when hot. The issue with this theory is that there's no squeaking or squealing typical of old/slipping belts.
2) The R134a refrigerant is low - this could be when the car is cold all refrigerant is collected back in the reservoir so the compressor has something to work with then engine starts, once the system is hot the refrigerant is dispersed all over the system and thus the compressor shuts down due to not enough R134a in the reservoir for it to work with.

Any thoughts?

 

First check the heater control valve to make certain no hot water is flowing through the heater core. If the valve is faulty and allowing the water to flow, the heater core would naturally get hotter as the engine comes up to temp and overcome the incoming cold air.
If working correctly, put gauges on the unit to check pressures.

 

If you get some pressure gauges, then hook them up and let them run. Hook up both the low and high side. You need to watch the readings as the system is running and then not running (cycling). If they pressure dips low enough, the low pressure switch will turn the compressor off to keep from damaging it. If you see the pressure dip, then you could need more refrigerant. If they pressure does not dip, then you could have a bad low pressure switch.

Post up the high and low side readings both at rest and with the compressor. Also, post up whether the pressure moves up/down or stays stable.

You will get more advice from there.

 

You would hear squeaking if the belt was slipping on the compressor.

If the heater valve was still open leading to hot air, the AC lines would still be ice cold and sweating. The fact that the lines get warm again lead me to believe that you are either low on coolant or have a bad low-pressure switch.

 

what if neither my fan or a/c come on for a few minutes after starting the car, then suddenly comes on and blows ice cold and fan works as usual?