I have not been able to find what is causing this yet. I can tell you what I suspect and my next step is. I will be replacing the pressure sensor as it controls the load on the compressor, I had it back in the ac shop and my pressures are fine and when I had the codes ran it came back with a press or sensor code stating pressures were too high. This is just my theory. I will report back when it is replaced.

What r your symptoms?

 

It was not really cooling so I refill the gas, and it was fine, just around 2 weeks, I notice below:

1. If I stop the car, just a few minutes the AC will blow warm air
2. Sometime, it just simply blow warm air, until I run the car after few minutes AC will start blowing cold air

Now it's totally blowing hot (not even warm) air

 

I would have a shop check the pressure first before anything else. It could be just a leak and needs a recharge.

I still haven't found my problem yet, hoping someone had some advise.

 

Totally random (and I might start a new thread for this) but for those of you who have been messing with this A/C system maybe this will help or you can shed some light on it.

I was driving home yesterday - very hot day out, and I immediately get slammed in stop-go traffic for about 45 minutes. Typically for the first 10 min my A/C will cycle on and off a few times. When it shuts off it's BRUTAL (these things are giant greenhouses!)

BUT yesterday, my ambient air temp read 78 degrees. Except it was 92 out. I guess I Wasn't going fast enough for it to update. It would seem that not only the visual air temp number won't update, but I believe the vehicle computers will use the last known air temperature as well till the vehicle speed is fast enough to update!

Anyways the entire time I was stuck in traffic and it read 78 degrees, the A/C compressor NEVER cycled off, not even once. By the time it updated I was moving fast and it still didn't cycle.

Mine typically cycles when it's been sitting all day at work, it's very hot out, and vehicle speed is fairly slow or there's stop-go driving. I know you're talking about some different issues, but maybe this helps some also.

edit: in any event my point was that it appears the ambient air temp impacts how the A/C engages and disengages. I'd assume it would have a typical pressure switch, but in typical LR fashion it appears to be more complicated than that.

 

Update: replace pressure sensor with LR new one. Worked for about 20 minutes. Blowing cold 48 degrees when it works and 80 plus when it doesn't. The pressure equalizes when it blows warm and then when compressor kicks on it goes back to normal pressures on each side, meaning the av compressor is turning off when it blows warm? Anyone ever replace ATCM?

 

I tried a know good ATCM swap and had no change still not working. So today I checked to make sure I had power to the AC compressor which I do. I am now wondering if this Denso Compressor's internal control valve is bad. Amazon will be refunding my money as soon as I return the compressor. I am beginning to think that these control valves are the problem with our compressors and am thinking of purchasing the valve and swapping it into my original compressor just to see what happens. Anyone have any experience with replacing the control valves. I already have the original one out as it is easy to remove just looking to see if anyone had any success with this?

 

when you say the pressure are normal what are they? the 450 psi you mentioned earlier is not a normal head pressure and your pressures change with temperature.

 

I'm starting to think you have something freezing and causing a blockage. Two things to confirm:

1. The system was completely evacuated before being recharged. Moisture left in the lines could freeze in the evaporator.
2. Do you need to replace your expansion valve?

Some dated but interesting reading here that sounds similar to the symptoms your described: Denlors Auto Blog » Blog Archive » Car A/C Stops Cooling or Working After a Few Minutes

 

It's always a good idea to replace the condenser and the evaporator; two main components of the system. You mentioned in your first post that you changed the condenser/drier but maybe you meant receiver/drier which is a totally different thing. You used to be able to flush evaporators and condensers but the way they are made now it's not really possible. You might have a blocked or partially blocked evaporator which would explain the higher than normal pressures. The flow is being restricted by the evaporator coming from the compressor therefore the pressures increase. When a compressor fails, assume contamination and change everything (compressor, receiver/drier, expansion valve, evaporator, condenser, o-rings). I'm surprised a shop wouldn't have done this - air conditioning 101...

 

Thanks for the advise. I will keep you all posted. I suspect control valve as the compressor will not even cycle on. From what I am finding these go out in the compressor 80 to 90% of the time when the compressor fails. Most places just put in a new compressor instead of swapping the control valve. Tomorrow I will be wrenching and Monday taking to AC shop to have it filled back up. Wish me luck.