Ok guys I hope you can help. How can I test the pressure switch on my air conditioner before replacing it? The compressor won't engage yet it was working perfectly when I parked the car two weeks ago.

Being that the relay was inexpensive, I bought one and changed it hoping that would be the problem.

Are there any other fuses or relays I need to check 1st before removing the pressure switch?

 

Does the condenser fan run when you turn on the A/C?

Have you voltage tested fuses 13 and 35?

 

The condenser fan does come on. I have not voltage tested those fuses. I'm guessing they are #d and easy to find?

 

Test 1

1. Turn key off.
2. Unplug ECU connector A.
3. Turn key to ON(II).
4. Ground the Blk/Red wire terminal at pin A15 of the ECU connector to the metal frame under the dash.
5. Did you hear the compressor clutch engage and disengage (click) when you ground and unground the wire terminal?

Do you have a multimeter or test light?

 

I do have a multimeter. It's been raining and snowing here for two days so I might have to wait until the weekend to run that test. Thanks for your help so far. I'll let you know as soon as I can.

 

So I'm trying to find fuse 35. Is it under the hood?

 

In the under hood fuse box.

 

FYI - The FAQs sticky has nice fuse box diagrams.

 

Got it. Thanks. Both 13 and 35 have voltage in the high 13s. So I'll check the cpu black/red to see if the compressor clicks.

The compressor clicks from the CPU grounding test. So I'm guessing this is low R134A?

Or is it the cycle switch?

 

Sounds like a bad ECU to me. There are a few more tests to confirm. Do you have a multimeter?

 

I do have a multimeter. What's next? And thanks.

 

Test 1:

1. Remove condenser fan relay from hood fuse box and also unplug the pressure switch near the condenser.
2. Turn key to ON(II).
3. Measure voltage to body ground at Blu/Red wire terminal in the unplugged pressure switch connector.
4. What is the voltage measurement?

 

Voltage reads 0.39

 

This^ is a problem. The voltage reading should have been 5V, which comes from the ECU.

Test 2:

1. Turn key off.
2. Reinstall condenser fan relay in hood fuse box.
3. Reconnect the plug to the pressure switch.
4. Unplug ECU connector B.
5. Turn key to ON(II). Turn A/C button off.
6. Measure voltage to body ground at pin B5 (Blu/Red wire terminal) in unplugged ECU connector B.
7. What is the voltage reading?

 

Here's the latest. I went ahead and purchased another ECU just because it won't hurt to have another one later. I swapped it out and still no a/c. With the ac on max and button pushed there is no voltage going to the single wire leading to the compressor. I've checked as many grounds as I could. What should that voltage be reading? And do you recommend a way to power up the compressor just to check operation?

 

 

You're on your own if your strategy is to take wild guesses and replace parts randomly. You don't need help with that.

 

I'll listen up and follow ur lead. I appreciate the help.

 

Why did you stop testing? I gave you my lead a week ago in post #16.

 

I'll conduct tomorrow. Busy at work with little time to spare last week. Thanks again.

 

I went back to the step where you told me to take out the condenser fan relay and test the voltage at the pressure switch with ignition in position ii

The voltage was 12.05.

This is the 1st chance that I have had to start testing again.

I'm not sure if I had a false reading the 1st time

 

Good. Was the new or old ECU installed?

Now ground this^ wire with the key in ON(II).

Do you hear the compressor clutch engage (click)?

 

The 1st time I checked the voltage at the blue/red pressure switch wire I got a reading of .39

The new one is in.

 

This^ is likely why the voltage reading changed. The old ECU was bad. Do the wire grounding test I just posted.

 

When I grounded the wire the fan turned on and the compressor made a noise