AC Troubles

[shakenfake]

Okay I have had this up on two other boards but I'm at a loss so coming here for a third opinion. My AC will not kick on. The compressor will kick on if you jump the relay or if you command it on with HPTuners but it will not come on when I turn it on with the HVAC control module. I HAVE tried swapping control modules. I have checked all fuses and they look good but I could probably swap them all out with some fresh new fuses to fully eliminate the doubt in that area. I had the pressures checked and they came out good.
When I have the low pressure sensor config set on HPT it only shows 0V. I do not think it is the sensor because even if I remove the harness from it there is no power coming to it.

I'm at a loss. Any ideas? My first thought is broken wire from HVAC to PCM. One of the reasons why I think this may be the case is because when I got my truck back from the trans rebuild both the AC and the Radio did not work. Radio had a blown fuse and would not come on at all. I'm thinking some wires must have touched and messed something up

Edited April 18, 2022 by shakenfake

[sefiroxx]

I don't have the repair manual in front of me. . . .

 

There is a check wire loop that goes thru various switches to verify that everything is good before activating the compressor. You can unplug the harness from these and insert a jumper wire to complete the circuit. On basic systems this includes the hi and lo pressure switches.

[shakenfake]

I have no idea about the check wire loop. 

I believe that the 1999 only has the low pressure switch and not a high pressure. Just one that is in the accumulator. 

If you are talking about that sensor then no, I cannot jump it as there is no voltage coming through the harness.

[richard wysong]

high pressure is on the rear of the compressor. you may be right on the broken wire if it can be commanded on with the scan tool. scan tool should tell you if it's being commanded by the control and possibly the status of the high and low switches. Why would having the trans fixed affect the radio etc? does the radio work now with a new fuse?

[shakenfake]

I had mentioned the trans because that is how it was returned to me from the shop. My uncle’s trans shop did the rebuild for me and I got it back no AC or radio. 
 

Yes a new fuse fixed the radio. 
 

I cannot see the status of High and low pressure switches, thanks for telling me where it is btw, HPTuners just allows me to turn the compressor on or off. 

[richard wysong]

A scan tool that is bidirectional may help you narrow it down. snap-on , autel, tech II etc. maybe your uncle has 1 you can use. just for giggles try jumping the low switch on the accumulator. seems to me I've run into this before and that kicked it on but it might not have been on a truck. I must be gettin old, 

[shakenfake]

@richard wysong Uncle and I are not particularly cool right now after me receiving my truck back in the condition I did. Long story not a big deal.

My girlfriend's father does have an Autel that I could borrow but I may try and pick up a Tech II.

 

Low switch is not receiving any power. I am unable to jump it. When I touch it with the test light nothing comes on. I'm not sure what would cause the low switch not to receive power.

[richard wysong]

the reasoning behind jumping the connector is just to get continuity in case it uses ground instead of 12v. paper clip may work and it eliminates that as the problem

[shakenfake]

Ah I have learned that the low pressure switch is a switched ground so obviously it won't get power. BUT that being said I think I may have found my problem

Originally I was thinking something was in the dash as well but last night I had a sort of epiphany

Looking at this diagram, which is the proper schematic, you can see that there is a wire coming from the PCM to the low pressure switch. Seeing as how I cannot jump it I am willing to bet that wire is crushed somewhere in the harness from when I had my trans pulled out and put back in.

[richard wysong]

maybe they pulled on the harness and broke the wire. if you can get a pinout of the ecm it shouldn't be hard to do a continuity test and run a new wire if needed. hope the tranny rebuild works out better than the installation

[shakenfake]

Trans has been fine so far. Put about 800 miles on it so far

[shakenfake]

Fixed

 

don't wanna talk about it...

[richard wysong]

LoL

[richard wysong]

just curious. what was it?

[shakenfake]

compressor unplugged lmao