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Need help! Car A/C not working. Shop can't figure it out

So I have a scion tc 2012 and the A/C no longer works properly. The AC blows lukewarm air (seems to just blow whatever air is outside) when I press the AC button, it doesn’t kick on the compressor. The heat works fine. I took it to a shop and they tested the pressure and said it was good. They can plug in a scan tool and make my car blow cold air but it won’t work without the scantool, the scantool can kick on the compressor. They checked all fuses and relays. They tried replacing A/C amplifier and they tried replacing (A/C switch?). Now they want to charge my $350 to fix drier and evaporater. If that’s not it they want to replace the compressor.

This is getting expensive fast, and they haven’t even actually diagnosed the problem!

Any ideas what this could be?!
Thank you

EDIT: Also the radiator fans don’t seem to power on either.

You need a new a/c button. A new compressor will stay off just like ur current compressor. Your techs are not bright. Go see new techs.

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Without a wiring schematic I can’t begin to tell you where to look, but will say that the drier/evaporator/compressor is not likely the problem.

I’ll take a look on the internet and see if a wiring diagram can be found. One big unknown to me is whether or not the low pressure cut-out switch has power to it and if so whether or not the power is going through the switch.

I believe they said something along the lines of their is 12v power going in but not coming out. I’m not sure what part they were referring to.

I just find it strange that It can be powered on and off with a scantool. It makes me believe all the components are working, ans something electrical is not working properly

Joshtalks, I agree, seems to be an electrical problem. I’d just turn on the AC switch, and use a voltmeter or test light to trace where the 12 volts from the switch goes away. But you will need the wiring diagram.

And the mechanic should be able to do this in his sleep.

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If they can get the AC to work with a scan tool, the heater/AC control assembly requires replacement.


I’ll give that a try!

Was the light in the A/C button blinking?

Sometimes the A/C amplifier can’t read the lock sensor in the compressor, this doesn’t show on the scan tool so this can be challenging. If there is continuity in the lock sensor circuit the problem is in the amplifier but not always. Since the A/C amplifier has been replaced the problem may be with the compressor however you mentioned an evaporator repair so I wonder if they found a problem with the evaporator temperature sensor.

The light was never blinking. The light on the AC button still lights up but the shop isn’t positive on what it is. I’ve taken it to the shop four times now and it seems it’s just trial and error and I can’t afford to keep buying parts I don’t need. There next ‘step’ was the evaporater and drier, If not, then the compressor. So I am going to take it to a different shop and get a second opinion.

They return the car to you 4 times unrepaired? You have been too patient.


Take it somewhere else.

Compressor, evaporator, drier?

They got it to work with the scan tool?

So those components must be working!


Yeah haha they were just doing trial and error. They weren’t charging me after the first two trips then they wanted $350 for another ‘maybe’. So anyways, I took a look at it myself and it’s strange. My AC compressor clutch is engaged, spinning, whether or not my AC is on or off. I tried spinning it myself when the car was off, no budge because it’s stuck engaged. So it’s engaged at all times, and it’s not blowing cold air. I’m beyond confused and more so I don’t understand how it works with the scantool anymore. Sigh.

This AC shop will be closed very shortly. I already see cobwebs in the corner.

Ambient temp sensor bad? Check Mechanic Files link above for a new shop in your area.

One offbeat idea, perhaps the AC is working ok but for some reason the vent doors inside the passenger compartment aren’t routing the cold air into the car. Do you notice any weird clicking noises under the dash OP?

You need a better shop. Clearly the one you’re taking it to isn’t capable of doing the diagnosis necessary. Clearly they’re limited to whatever the computer tells them.

Sorry, but the solution lies elsewhere.

Agree! A/C work is not rocket science, but it takes a specialty shop to quickly diagnose what’s wrong; this shop seems to be guessing.

We have a local shop called Auto Temp who do nothing but and also install audio equipment and accessories. They will tell you how far your compressor is worn and what needs to be changed or cleaned out.

There are lots of these shops around the country. Dealers often don’t bother training an A/C specialist since newer cars don’t often have A/C problems.

I tried spinning it myself when the car was off, no budge because it's stuck engaged.

Try taking the belt off and turning it.

So I just got my car back from the second shop. They told me that they have no idea why it won’t work. They plugged in the scantool and got it working through that aswell. They only charged me 10 bucks because they felt bad. I am at a loss here. Nobody can figure out the problem and this shop recommended I take it to the dealership to take a look, which will cost a fortune I’m sure.