Hi -

I just bought a used 98 SC300. The A/C is nice and cold every time I start up the car when the car is cold, but then like clockwork, after about ten minutes, it's just as though I turned the A/C off, and will remain so until I park the car for a while. If I turn off my car and then on again this doesn't make it cold again, apparently the car has to sit until it gets cold again.

The a/c was completely redone just before I bought the car, the seller gave me the receipt. (Unfortunately that repair shop is far away from me and never answers their phone or returns my calls.)

Any ideas what could cause something like this? One person suggested it could be my heater valve.

 

sounds like you just need a recharge. I would rule out a leak as it gets cool then looses it.

 

But isn't it strange that the a/c is cold every time the car is cold, but stops being cold every time the car warms up? As I said, it's like clockwork, happens every time exactly the same. I would think if it needed a recharge it would never be cold.

Could it be the heater valve as suggested to me?

 

What does "completely redone" mean? Was it evac'd and rechargd? Was the compressor replaced? Was this work done because the previous owner had the same issue as you and this was to fix it? If so what was determined to be the problem then? Didnt you test drive it before you bought it Im sure you drove it for more than a few mins and it didnt do it?

 

The compressor and expansion valve was replaced (along with other parts), and it was evacuated & recharged, they paid $1150.

I test drove it for about ten minutes I suppose. It was cold the entire time. Just several miles down the freeway on my way home it got warm, I was depressed to say the least.

Interestingly, I just started it and have left it idling for about 45 minutes now and it's been cold the entire time. Apparently I have to be driving around for it to get warm, if that is any kind of indicator.

 

OK so after about 45 minutes of being parked idling it stopped being cold. So it happens while parked idling but stays cold much longer than if I'm driving.

Also I should add that I ran the a/c diagnostic check (before and after it got warm) and it came up as 00 (no errors).

 

 

Here's a new thing I discovered last night: if I leave the A/C off while I'm driving for a long period of time then suddenly turn on the A/C, it is cold. So it has nothing to do with the car being warm.

Please help... I really can't afford to take it to a Lexus dealer... I spent all my money on this car

 

Hmmm...if they did all that and evac'd and refilled I am not sure. Is there an independent mechanic you can bring it to at least for a diagnosis or to test the system? Sounds like when its under load it fails...is there such a thing as airpockets if it was not evac'd and recharged correctly?

So it shows what was replaced does it say why they did the work? Does the previous owner know? I know this sounds crazy but just throwing parts to fix a problem sometimes doesnt fix the problem. If the mechanic did a diagnosis and the previous owners complaint is what you have then they might not have resolved the problem

 

hmmm maybe the a/c relay is failing under heat? or expansion vale stuck i really couldn't say unless i was testing the car myself

 

Sounds like the expansion valve gets stuck closed. Sometimes it will work perfectly, and sometimes it will be cold then get hot.

I replaced mine on my previous car and things worked perfectly. You may have a faulty valve.