Look on page 6 of the 61-361 Test-Pro Multimeter instructions (pdf, 530k, Rev 5). EDIT: That pdf is on the link you provided on your last post.

That shows you were the diode setting is located on the meter. The meter should beep (closed circuit) when you touch the red and black probe together. The meter should not beep when the leads are not touching.

Just touch the red lead on the meter to the blu/red wire. The black lead on the meter can touch any bare metal bolt. Let us know if the meter beeps or not.

 

I hooked the black to battery ground and red to red / blue and I get the beep.

What is this telling us?

Also I re did the jump of blu /yellow Blue red and wanted to check if ac came on and it did not. The fans come on in position II and stay on when car is started but no ac commpressor kick in.

This jumper should make both run as stated above?

Also do not forget the back thermostate seems bad with jump test. I am sure all same ground issue/

 

If you have 12V on the other two wires, then the a/c thermostat is bad.

 

The ground path for the compressor relay drive coil circuit is through the ECM. ECM gets a closed/open signal from Thermostat completing ground path that it uses to know when to drive the compressor relay coil.

good luck

 

TH, I see what you are talking about.

I am going off of the test that the blu/yel wire going to the thermostat had no ground. Then the blu/red wire had ground.

Johnno0213 - Redo the test on the blu/yel wire on the pressure switch using the diode (beep) test. Make sure the thermostat is plugged in and the a/c switch inside of the car is turned on.

TH - What always confuses me on the wiring diagrams is the ECU B5 pin. Does the thermostat just have an open/closed signal for the ECU at that pin where the ECU would read either 12 or 0V?

 

I will run through the test again and post findings.

I am getting more confidence with the meter and test light.

I will also study the wire diagram.

Could it be the controls on the dash?

 

It is not the dash controls, because you had ground when you tested the ground side at the thermostat.

In the shop manual, there is a diagnostic tree for when the compressor and the fans do not work. It is kind of the tests we suggested. Since you are more confident with the volt meter, you should be able to move through it quickly.

 

"TH - What always confuses me on the wiring diagrams is the ECU B5 pin. Does the thermostat just have an open/closed signal for the ECU at that pin where the ECU would read either 12 or 0V?"

When thermostat closes, the B5 pin will see ground and when open will see 12V. ECU somehow uses this to trigger AC compressor relay. There is no detailed wiring diagram of the circuit board.

good luck

 

During idle, the ECU has to "know" when the AC compressor clutch is switched on. That's for idle-control, so it can open the IACV a fraction of a second before switching the AC.

I SUSPECT that it's also done that way so the ECU can prevent the AC from switching on, in case of wide-open throttle, or also if the coolant temperature is too high.

 

Agree w/ Jim. There's no "map" of all the times ECM uses the thermostat open/close signals to control compressor.

However the primary reason is to prevent freezing of the evaporator. There is no other path to disable the compressor other than through the ECM control of AC compressor relay.

good luck