A/C suddenly quit

[ktb973]

Hi all!! Hope you can help me. I've never worked on an ac system before so I can use any insight.

The A/C was working fine the other day and we stopped to get gas and when we got back in it wasn't working. Upon further inspection I realized that the compressor wasn't kicking on. My first thought was the fuses and relays and I checked all of those they were fine.

I've done some research and realized that the compressor will not engage if the coolant pressure gets too high or too low. I thought it must be too low so I decided to try to add some but when I put the recharger on the low side the gauge is maxed out over 100 psi!! The car was running with the ac on max and doors open with fan on high.

My guess is that without the compressor running I'm looking at static pressure in the system and in order to see the real pressure I have to get the compressor running. Is there a way to fool the compressor into running so I can see what kind of coolant pressure I have? Or is my assumption all wrong on why the pressure is so high?

Normally I'm not opposed to tinkering quit a bit before giving up but I know that I could really damage my ac system if I make a mistake.

Thanks for any help

[CTScott]

Does the little indicator light on the AC switch light up when you press the button?

The compressor's electric clutch just has a two wire connector. The white/black wire is ground and the light green gets +12V from the AC amplifier when it wants the compressor to spin.

[YAR1S]

http://www.kitchendetailsanddesign.com/wp-content/uploads/2010/03/mr-bill-ohh-nooo-magnet-c11751410jpeg.jpg

[ktb973]

Yes the light does come on. I've found the manual for the ac.

http://www.etimago.com/yaris/repairmanual/Air%20Conditioning.pdf

I haven't dug into all of the electrical yet, just the basics so far such as fuses, low pressure switch voltage and voltage to the compressor. Pressure switch was fine but that voltage to the compressor was under 3 volts.

I am capable of tracing it all out if it sounds electrical to you guys. I was just wondering if it's something simpler that I don't know about.

Thanks

[fnkngrv]

Have you done anything under your hood that could have possibly impacted your system?

[ktb973]

Nah, we bought the car brand new in 07 and nothing's been done to it. This is the first problem that we've ever had and my wife already has 138000 miles on it.
Have you done anything under your hood that could have possibly impacted your system?

[CTScott]

Yes the light does come on. I've found the manual for the ac.

http://www.etimago.com/yaris/repairmanual/Air%20Conditioning.pdf

I haven't dug into all of the electrical yet, just the basics so far such as fuses, low pressure switch voltage and voltage to the compressor. Pressure switch was fine but that voltage to the compressor was under 3 volts.

I am capable of tracing it all out if it sounds electrical to you guys. I was just wondering if it's something simpler that I don't know about.

Thanks

If the light is on, then the AC Amplifier (ECU) is alive (and the A/C fuse is good). At this point, it would be ideal to be able to read the DTCs from the AC amplifier, but unfortunately that particular ECU will only report its DTCs via the Toyota TechStream tool.

So, I would verify the voltages on the pressure sensor and the evaporator temp sensor, and if they are both OK, I would probably opt to have someone plug in a TechStream tool.

It would be nice to be able to plug it into a Toyota Techstream

[ktb973]

If the light is on, then the AC Amplifier (ECU) is alive (and the A/C fuse is good). At this point, it would be ideal to be able to read the DTCs from the AC amplifier, but unfortunately that particular ECU will only report its DTCs via the Toyota TechStream tool.

So, I would verify the voltages on the pressure sensor and the evaporator temp sensor, and if they are both OK, I would probably opt to have someone plug in a TechStream tool.

It would be nice to be able to plug it into a Toyota Techstream

I have a code reader from mac tools. Think that will tell me anything? I'll try it anyway. The only reason I haven't yet is that it was in my car that my wife is driving now.

[CTScott]

I have a code reader from mac tools. Think that will tell me anything? I'll try it anyway. The only reason I haven't yet is that it was in my car that my wife is driving now.

No. It would have to support the Toyota diagnostics protocol, as opposed to OBDII.

[ktb973]

Thank you for your help. I think I will just take it in rather than going down a rat hole trying to diagnose it myself. It does seem like an electrical problem I suppose.

[bankrobber]

On my 95 Dodge Ram I took a paper clip and touched both sides of plug that went to compressor. That manually ran compressor when I charged it with freon.
I have noticed a few times after a quick stop at the store the A/C will blow warm and then I push switch in and out a few times then it will work normal again.

[ktb973]

On my 95 Dodge Ram I took a paper clip and touched both sides of plug that went to compressor. That manually ran compressor when I charged it with freon.
I have noticed a few times after a quick stop at the store the A/C will blow warm and then I push switch in and out a few times then it will work normal again.

Man I thought about doing that except I was gonna jumper mine straight from the battery but I'm afraid it might have unintended consequences.

[CTScott]

Man I thought about doing that except I was gonna jumper mine straight from the battery but I'm afraid it might have unintended consequences.

You don't by any chance have someone close by with another Yaris? I took apart an AC Amplifier last night and a tiny surface mount transistor drives the clutch. It is entirely possible that its bad, and in that case, swapping the AC amplifier (it is mounted just to the right of the gas pedal) would quickly tell you if that's the issue.

[ktb973]

You don't by any chance have someone close by with another Yaris? I took apart an AC Amplifier last night and a tiny surface mount transistor drives the clutch. It is entirely possible that its bad, and in that case, swapping the AC amplifier (it is mounted just to the right of the gas pedal) would quickly tell you if that's the issue.

Wish I knew someone that had a yaris. Part swappin is my favorite kind of troubleshooting. It was over 100 here with no breeze so I didn't even look any more at it today. Gonna start calling shops tomorrow I suppose.