Yes I am seeking answers to specific questions at this point in the troubleshooting. The voltage he wants me to check for goes to an unnumber/unnamed relay in the under hood box on all the diagrams I have. There are five relays in the underhood panel. I know what four of them do and they are shown clearly on the schematics. The fifth one is in the row of three relays on the right side of the under hood fuse/relay box. Here is my previous post:

"In looking at the pressure switch for the EX V-6, it shows pins 1 and 4 normally closed (I assume pressure is "normal" to remain in this closed position. Pin 4 goes to the Climate Control Unit and Pin 1 goes to some relay module(not named) Pin H2 with a "control block" labeled box shown inside the "relay module" labeled larger box and this unlableled relay module connects to Pin 25 of the Guage Control Module. Pin 2 shows a chassis ground and is shown normally open to Pin 3. When closed, Pin 3 connects the ground via pin 2 to the ECM/PCM Pin E14.

There is no ground on pin 3 when checking the plug side removed from the pressure switch. I did not check for 12vdc on pin 4 or 1. Not sure what it would mean without more detail on the mystery relay module.

I did notice that the Guage Control Unit supplies a signal to the ECM/PCM on pin E24 called COM SIG LO and Pin E11 called COM SIG HI.

I wish I knew what that relay module does that the pressure switch pin 1 blu/red wire goes to. Frustrating as it doesn't identify anything but its location and the lid for the underhood fuse/relay box only has stupid unclear pictures."

I swapped the relay with the other one of the same type with no change in symptoms. I can certainly check for grounds and voltages in off and on key positions at all four pins of that relay but unless I know what it is exactly and its pin numbering etc. I can't troubleshoot it any further with out more detail.

I do appreciate the help thus far.

 

Go to page 21-30 of the shop manual. That is the testing procedure I am giving you. I believe the relay module is the large metal box that is part of the engine bay fuse box. The wire should have >5V.

I have spent more time typing this response compared to the time it takes for to do this test that is in the shop manual.

 

Ok. I will check for any voltage at Pin 1 or 4 of the pressure switch plug and report back. Unfortunately, I do not have a shop manual yet.

I never noticed a large metal box that is part of the engine bay fuse box, but will look again. Thanks.

 

On the pressure switch plug, Blu/Red has 11.08 v and Wht/Grn has 11.8 volts with the key on and nothing with the key off. BLk has a ground.

I did notice a small black box attached in front of the engine fuse box. Inside is a single relay different from all the rest and an empty 4 pin socket. The relay has a different socket from all the other relays in that it has 5 pins total; three in a row and two in a row perpendicular to the three. No labeling or markings that I could see.

 

Ok, key off, check for continuity on the pins #1 and #4....see pic.

 

There is continuity between Pin 1 and 4 of the pressure switch.

 

Does the blower work inside of the car? Also, does the heat work?

 

The blower inside the car does work at all speeds and the heat works also.

 

Update: The temperture turned hot here with about a +20 degree change. I wanted to see if the fans were working when the engine got hot. Both fans were running so I thought let me double check my symptoms in the morning when the engine is cool. Both fans run now when I turn on the A/C which was not happening when I began my troubleshooting. What the heck?

The compressor clutch still does not engage. If I jumper Pin 4 and 2 on the clutch relay, the clutch does engage and I get nice cold air.

 

Did you ever try shorting the hi/lo pressure switch to see if that enables compressor?

If cooling fans come on w/ AC switch, the compressor is likely being disabled by ECU not supplying ground to AC comp relay.

good luck