Ac shuts off after seconds.

So I have searched threads and found several with this exact same issue but no answers to the problem. My ac was running fine then it just stopped working. If I hit the switch it lights up and compressor engages for 3 to 4 seconds then it stops. Hooked up gauges to low and high sides and hit the button and it wouldn't move them much. Called a guy who is a toyota tech for advice and he said it was most likely the clutch which is on back order, so I ordered an aftermarket compressor and clutch for half the price. Installed it yesterday and recharged it and it's still doing the same thing except now the gauges were moving and I can feel it getting cold air if I keep pressing the ac button. Don't know what to check next. Can I bypass the pressure switch to test that or what should be my next move?

 

Sounds like a relay might have gone bad.

 

When the A/C light turns off after a few seconds it's because the A/C Amplifier isn't getting the correct RPM signal from the Lock Sensor on the compressor.

Since it sounds like the clutch failed on the old compressor it's a good possibility the Lock Sensor on the replacement compressor is no good. We have seen issues with Lock Sensors not working properly on aftermarket compressors.

 

I swapped horn and clutch relay with no change.

 

How can I test it?

 

You need an oscilloscope to see what the sensor signal looks like.
Did you save the old compressor and sensor?

 

I assume from your posts that it’s best when installing a new clutch to use OEM and then also either get a new OEM lock sensor or move over your old one (if that’s possible)?

 

Probably time to just get it to a tech.

 

Yes I did save the old one.

 

I haven't personally had it happen but I don't get to work on many Toyota's but I've talked to some of the techs that lurk on here and they have had some issues with lock sensors on aftermarket compressors, even from name brands like Delphi.

 

The oem ones are on a national backorder. Looks like they have a known problem just won't admit it.

 

Clutch failure seems to be more common on 3rd gens than the lock sensor failing.

I haven't even seen where Toyota services the 3rd gen lock sensor separate from the compressor, the part number they show on the diagram is for a 2nd gen compressor.

The sucky part about the 3rd gen is you have to recover the refrigerant to change the sensor where the 2nd gen was just bolted to the bottom of the compressor.

 

Yep and recovery is the only tool I don't have access to

 

Oh and by the way when I was just driving it if I was at like 2000 to 3000 rps the ac would stay on at least twice as long

 

Sounds like you've got the original compressor w/ original lock sensor.. but the lock sensor doesn't like the signal from the aftermarket clutch coil

Its possible the reason it stays on longer when running higher rpms is because the signal frequency (amplitude?) Is higher so the lock sensor can see it better?

Sounds like a abs wheel speed sensor when the tone ring gets chipped or cracked. At high speed the sensor doesn't notice the crappy spot in the sine wave signal. But at lower speeds, like in a parking lot, it will see the anomaly in the signal and cause erratic abs activation

Sucks that oem is on backorder.. maybe look closely at the wiring for something chafed or damaged?

 

Can I swap this?

 

Wait I got confused, I thought you replced the clutch only with a aftermarket. I reread and you installed a whole compressor..

Yes I'd try to get the old lock sensor installed into the new compressor. That may fix it

 

Hard to say without scoping the signal, 2nd gens have a digital hall effect sensor. I haven't really studied 3rd gens much.

You can but not while the system is under pressure.

 

Yeah swapped the whole thing

 

Always, always, always keep the lock sensor from the old compressor. The one that comes with the aftermarket unit will never be as good as oem. They totally go cheap with that stuff on purpose. To keep the costs down

I learned the hard way a few years back, Dm mentions it now and then