williamb82

93 GS300, just over 397k miles.


I have been fighting this gremlin for awhile now. Everything I could find indicated the clutch was slipping, or the compressor was locking up.

I changed the AC compressor relay. Same issue.

I replaced the compressor, expansion valve, drier, all schrader valves and o rings, added the correct amount of oil, vacuumed it, charged it etc... and it still does this.

Sometimes, I can hit the ac button to turn it off and back on a few times and it will stay on and work great. others, I can do it the entire time I am driving and it will not stay on. I cannot find anything wrong, at all. If I use a jumper wire in place of the relay, the AC works fine, though the idle rpm is too low as it is not the ECU turning it on.

I thought maybe somehow it was the high side pressure going too high. I hooked my gauges back up. It is cutting off at about 145psi on the high side, so unless the switch is bad, I don't believe it to be a pressure issue. The only other thing I can think of would be the sensor on the bottom of the compressor, as I had to swap it from my old one to the new one, but if this were bad, I would expect to have the issue all of the time, and not just randomly. Sometimes I turn the AC on and never have a single issue.

Has anyone else run into this issue, or have suggestions on what could be the cause? It is really pissing me off. Right now its nice and cool out, so I would like to get it fixed before it gets to be near 100deg every day again here in FL. Thanks.

williamb82

Anyone? I have also replaced the serpentine belt tensioner in case it was allowing the belt to slip on the compressor, though it has never squealed. Same issue.

williamb82

I was able to get a TSRM. I followed the procedure to check the AC codes on the AC control unit. It shows codes 20, 21, 22, 23, 24, 25, 26, 27, 28, and 29.Most of these codes arnt even listed in the TSRM so seem to be bogus codes. Of the codes listed, they all have 2 common possible causes, bad ground, or bad AC control box. Since I know the grounds are all good as literally everything else works fine, and I upgraded my engine grounds long ago to 4awg, plus added extras, It seems the AC control box is in need of replacement.

TRACKMKIII

When I first bought my 94 GS I had the same problem and the problem turned out to be the ECU itself. One of the capacitors inside of the ECU was leaking which ia a pretty common issues for old Toyota models. I had the ECU rapairs and boom everything was great!!

williamb82

The engine ECU is fine. I have already replaced all capacitors in it. Or are you saying there is an ECU for the AC system? if so, where is it located?

The codes I listed are codes from the actual ac unit itself, not the Engine codes from the engine light flashing.

williamb82

Replacement AC control unit arrived yesterday. I installed it. Fingers crossed. I let it run for 10min with the ac on and it didnt flash or disengage the compressor. Also, does anyone know where I can get a replacement LCD for the ac controls? I know I got one and replaced it for my old LS400, but I havent been able to find one for my GS300.

williamb82

Still having the same issue. I am gonna try swapping the ECU out with one of my spares. IDK why that would have an effect on it but worth a shot I guess.