No A/C

NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
Hope you guys can help me out. AC stopped blowing cold. PIA part is the clutch cycles for about 5-10 seconds when the car is first started, then won't cycle anymore. Jumped the connector on the low pressure switch, no joy.
So far, I've checked for voltage on the low pressure switch (5v-low?), the fuse in the front fuse box (good, checked with a test light), and I swapped the relays for the AC and SAI (same part number on the relay, I think #33 and 44?, next to each other in the fuse box). I did have 12v on 2 of the wires on the relay, 0v on the 2 others.
Also, does this have a high pressure switch? I couldn't find it.
Really don't understand what seems to be low voltage on the connector for the low pressure switch.
Any help would be appreciated.
 

budwich

Member
Jun 16, 2013
2,027
kanata
"don't understand what seems to be low voltage on the connector for the low pressure switch".... it just means that the switch was open which I think means you don't have enough r134. Checked your pressures lately?
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
5V at the switch is normal (aka: reference voltage). If jumping that connector doesn't start it, then it's not the charge. Have you try to jump at the relay to engage the compressor?

I have a feeling it's the clutch, either the magnet or the clutch itself is worn. Usually to fix either is to remove the shim under the clutch plate.

The manuals do have the A/C diagrams.
 

NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
NO, haven't tried to jump the relay, was afraid of crossing the wrong 2 wires. I looked at the wiring diagrams after I got back in the house, and can figure it out. Never realized how much was on the circuit (PCM, fan clutch???).
Can anyone tell me why the AC clutch runs for 5-10 seconds, then shuts off and won't kick in again? Way back in the day, the pressure switches cycled the AC clutch, this ones SO different.
 

budwich

Member
Jun 16, 2013
2,027
kanata
The system also "actively" measures the pressure via the "pressure sensor" so there is a range of operation. You can force the clutch on by running voltage and ground to it.... but check the resistance first to ensure that "things" are OK there. Of course, the protections are built into the system for a reason and circumventing them especially in the "long term" is usually not wise. The real question is "what are you trying to do?"
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I meant to jump the relay as a test, not a long term solution. If you can get it to run more than the few seconds you are getting now, then there is something the PCM doesn't like and doesn't let the compressor back on. Although it seems it would not be the low pressure switch as you already tried jumping that, it could be the high pressure switch or the thermal switch which is located on the compressor. I don't know where the high pressure switch is but it should be somewhere on the high pressure side line. It might be near the compressor.
 

budwich

Member
Jun 16, 2013
2,027
kanata
I don't think there is a high pressure switch in the system (at least none that I have seen in wiring). The pcm monitors a pressure sensor and has operating ranges that it allows things to happen. IF outside the range (in either direction), it isn't likely to provide the appropriate grounds to cause component operation and the potential for a significant problem. The OP has not indicate if he has checked any pressures and appears to may want to "blindly run the system" or something else.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
You're right. No temp sensor but a pressure switch but it doesn't say if it's a high/low or what. I do believe it's a sensor rather than a switch since it's 3 wires and I have seen pressure readings in my Tech 2.
 

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NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
On the day I was testing it was around 90 degrees and the pressure with the engine off was ~100lbs. When I started the car with the AC on, it dropped to around 70lbs., the the clutch kicked off, and wouldn't go on again.
Followed the AC lines and didn't find a high pressure schrader fitting.
Anyone know where the pressure sensor mentioned is?
 

budwich

Member
Jun 16, 2013
2,027
kanata
have you got access to a "torque enabled" device. The app can read the pressures that the PCM is seeing from the system.

PS. I looked around on my 2008, and all the hoses from the compressor have no high port fittings associated with them that I could see.... plus there ain't a lot of room in / around the compressor to do "normal connection monitoring". You can see the pressure sensor for the compressor. My guess is that they use the "pcm monitor" to obtain high readings / any readings.
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
100psi static and 70psi running on the low side sounds really high to me and could be overcharged. I'd get it evacuated and refilled with the proper amount to eliminate that possibility. it certainly isn't the low pressure switch cycling that's for sure.
 
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NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
I thought the AC pressures, without the engine running, should be close to ambient temp. Am I wrong? When I start the car, the compressor runs maybe 5 seconds, then shuts off. In that time, the pressure drops to 70lbs. If the compressor stayed engaged, I might have AC. The last time I put freon in this was 2012, just because it was blowing warm, but still cycling. Worked great until a couple of weeks ago.
Mooseman- I spent lots of time going over the schematics from your download manuals (thank you), and found an 'HVAC' control module that I have no idea what or where it is, but there's wires that go to the PCM from it, which really surprised me.
Understand, I was a mechanic for 20 years, and got out in the early 90's. The procedure then was to jump the low pressure switch so the compressor comes on, and add freon until the low pressure side read around 30psi., with the system mechanically sound, no noises, etc., and cycling. When I jumped the low pressure switch and the compressor didn't come on I knew I was in trouble.
Next time I'm going to have the time to work on this is in about a week or two, I'll post what I find.
I do like the idea of evacuating and recharging, I could check the orifice tube for shits and giggles, and be sure I have the proper amount of 134A in it. Now to borrow the tool.
Edit: I missed the post with the AC schematic in it, and after looking at it I'm thinking the PCM is losing or disconnecting the ground. Realized the AC control module is the HVAC dash controls.
 
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NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
Finally got back to it yesterday and I think I found it. Took the alternator off because I couldn't follow the wiring harness to the high pressure switch which was what I thought was causing the problems, and wiggled the wires. Lo and behold, there was a wire broken inside the insulation.
Unfortunately, it couldn't be repaired as it was broken close to the pin in the connector, and being it was 4pm Saturday, no stores were open that had this type of pin.
I'm going to try going to the dealer and get a new connector with the wires and solder it in.
I sure do hope this solves the problem.
 
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mrrsm

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Oct 22, 2015
7,642
Tampa Bay Area
I realize that what you are trying to do with your Broken Wire Repair is somewhat akin to Opening Circus Tent inside a Phone Booth... but if you could memorialize your work with some Digital Images... Your Excellent" Seek and Find Diagnosis" will be very much appreciated my many Members facing a similar A/C Mystery in the future. This would be especially helpful with views of the A/C Compressor High Pressure Switch... which I suspect is located near the Top of the Aluminum Hi-Lo Hose Manifold at the back side of the Compressor (... surmised by @Mooseman in Post #6).
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Another suggestion could be to cannibalize one from a junker at a pick-n-pull. Dealer or anybody might not have them in stock anywhere.
 

NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
Yes, I'm expecting this to be at least one day off work to chase the connector down. Probably going to be another week or two before I get the parts together and get back to it.
I'm going to the dealer today to see if I can order it, if not I'll visit the junkyards. If that don't work I'll try getting the pins for the connector.
I do have the proper crimper but I don't think I can do it as neatly as the factory.
 

NJTB

Original poster
Member
Aug 27, 2012
612
Flemington, NJ
The dealer had to order the parts, and they came in Wednesday. The new connector was wired with 3 white wires (great), but a bit different, so had to buy a new, updated, high pressure switch. OK, no problem (both were $126, ouch). The connector came with heat shrink crimp on connectors.Took yesterday off work and got into it.
Removed the alternator, cut back the wires a few inches, put some regular heat shrink on the wires, crimped them on, shrunk them with a bic lighter, slipped the heat shrink tube over them and shrunk it.
While I was in there, the coolant sensor had been acting up, (it's another story) so I had a new AC Delco sensor to put in. In all my years, I have never run into such a pain in the ass. Since I didn't have the socket with the slot in it (18mm), I tried using a crows foot, to no avail. There's a relief cut in the block so the crows foot won't fit.
Off to the auto parts store to buy a socket. Went to 4 of them, everyone showed me an O2 sensor socket (7/8), and told me to go to another auto parts store. After the 4th store I was about to give up, then saw a Snap On truck in a gas station. He didn't have one, but he said let's try this.
What he did have was a fuel injector socket with the slot in it, 18mm. Oh joy, $59.
Back at it. Socket worked great, put every thing back together (that alternator is a pain in the ass), put anti freeze in it and started it up.
I was glad the coolant temp was where it should be, but still no joy on the AC. The clutch will engage for 5-10 seconds and kick off.
I've resigned myself to the fact it's going to have to be repaired at the dealer, so I'm making the appointment.
MSRRM- I wish I knew how to post pictures, for me it turns into a fiasco and the picture never posts.
 

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