TA_Freak

Ever since a shop that will go unamed busted the connector on my AC compressor, I've had issues with my AC. Pressures look good. When I jumper it's relay at 87 and 30, I can energize the clutch. Pressures look fine - 35 and 230. Doesn't seem to be getting the ground at the relay from the PCM's relay control. I know there's limited advice that can be given on a problem as such, other than diving into it. What are the low and/or high pressures on that system that would turn off the compressor?

jim9

My first visit this year shows another ac problem. Mine is a 2000 z/28 that sat for a year and now doesn't seem to engage the clutch. It partly took my last can of r-134, but no difference. Last year it ran cool, but became very noisy, so I refrained from using it. I'm still trying to locate component locations to learn about the system in these cars.
Good luck with your troubleshooting. I'm pretty clueless about theses things.

TA_Freak

Start with gauges. If you don't know what the pressures are in the system, you're flying blind. Don't just try to shoot a can of refrigerant into the system because it's blowing hot. If the clutch isn't engaged, you're pissing in the wind.

jetech

35psi is enough pressure to allow the low pressure switch to show continuity. You can easily check the switch by unplugging it's connector and using an ohm meter to check continuity.
230psi is also a "good system pressure while running. When the system is off (not running) the low and high side pressures will equalize. Making the pressure switch "see" above 35psi to allow the compressor circuit to energize.

jetech

Is the relay you are removing to jump the pins a known working relay? If the system runs when jumped there is not a problem with pressure switches. I would look at the relay and then the AC request circuit

TA_Freak

Yes. It's a good known relay. Swapped it with the fuel pump relay. That's the first thing that I tried before jumping/by passing the relay. After bypassing the relay and the coil energized, I looked at the AC request. I'm not getting the ground from the PCM's pin 39. I haven't gotten to it since. I'm going to manually apply the ground to the relay from the bottom with the relay still in to pin 86. I could temporarily run it like that seeing that my AC never cycles in 90 degree weather. LOL. But that will tell a lot.

TA_Freak

Well being able to energize the relay fine manually with a ground to 86. So with everything else checking out good, I decided to reseat the PCM connections.... and low and behold they were not even tighted. I was able to spin the two bolts with my finger! WTF?!!! After a little bit of nervousness due to the plastic pins retainer being cracked, busted and missing, I carefully got the connector on and tightened properly and now the ground is there and the compressor clutch is engaged! That will probably explain my intermittent cruise control.

jetech

Very nice. Glad to hear you found the problem. What kind of people do work like not installing the PCM connectors correctly? Jeeze!

TA_Freak

Right ... and with my recent build I don't know why they would have been loose. Maybe they bricked my PCM and it's a replacement. Nevertheless, tighten the damn thing down!

TA_Freak

Well ... not solved! Yesterday it worked briefly then the clutch disengaged. Back to the drawing board.

TA_Freak

Yesterday I jumpered the relay and the clutch engagement was intermittent. I could wiggle the wires that lead to the relay, fuse ...etc... and the clutch would come and go. I traced it to simply touching the 15 amp fuse for the AC/cruise. I pulled out the fuse and scraped it (oxide?) and that solved the connectoritous issue, as I like to call it. I still don't get the command from the PCM to ground the relay and energize the coil of the relay. Ongoing ......

jetech

I would check if the pin(43) got pulled back some in the connector maybe it's not making contact with the pcm. Are you getting 12v on circuit 762 pin 17 of the red connector when you turn the ac switch to the on position?

TA_Freak

Definitely - the next place to look. Been too busy to get back to it; fortunately my DD has good AC. Should be able to get back to it this afternoon.

TA_Freak

Despite not having looked at the AC further, I missed the TA, and decided to drive it to work this morning. The intermittent AC was not working and my windshield was fogging up. I put my special jumpered relay (soldered wire from 30 to 87) and drove. I knew that was potentially not a good idea. When the AC started blowing frost out of the vents, I pulled over and pulled the special relay out and put the regular relay back in. Side note - I am having intermittent cruise control as well. That's a major clue since the source voltage feeds both AC and cruise circuits through a common fuse.

TA_Freak

The AC request signal on pin 17 is good. It goes from 12v to 0v when turning on and off the AC. Also pin 18 does the same for the AC status signal. The AC clutch relay control on pin 43 stays at 12v. It needs to drop to 0 to energize the relay. Pin 14 red stays at 0 volts, which is the pressure sensor signal. Pin 45 blue stays at 5V which is the pressure sensor 5v reference. I'm leaning towards a bad pressure sensor switch at this point.

RevGTO

iTrader: (12)

That diagnosis fits your symptoms and AFAICT your voltage readings.

TA_Freak

So I thought I was good until I was driving it yesterday and .... hot air! GRRRRR! This is clearly an intermittent issue. Pretty sure it's fixed now. I fired up the Tech2 and in the special functions/engine output controls was everything that I needed. I commanded an AC request and the clutch kicked on ... while I was on, i went back to the 15A fuse that feeds 2 legs on the AC relay and the clutch started cutting off/on as soon as I touched or tried to move the fuse. I swapped the fuse and all is well. This was a case of assuming the worst instead of something that simple.

jetech

That happens to the best of us sometimes

TA_Freak

Indeed. So everything was fine after driving some 40 miles and the vents become hot. Got home and found the connector to the compressor hanging. The shop that did my build busted the connector so it won't stay on. One would think that a decent shop would tell the customer about the damage, knowing he's going to run into trouble with it. Nope! So after fricken with it for a while trying to solder an "extender" to the compressor, I gave up. I'm pissed.

jetech

You must have been really gett'in on it to make the connector fly off . Is this what they broke?