If anyone recalls I've been working on the a/c system on the 89. All kinds of problems.

Can someone test the a/c compressor connector for me? I need two tests:

1) car off - voltage test at compressor coil power connector (vehicle side) - both contacts
2) ignition on (not running) with a/c turned to auto (c68)- voltage test at compressor coil power connector (vehicle side) - both contacts

I'm trying to rule out a bad coil in the process of this. The coil is new, but even jumpering the wires with 12v I can't get the clutch to engage.

As stated, this is for my 89, but other year ranges with the same compressor (nippondenso) should apply.

I appreciate the help.

Matthew

geez... I don't remember off hand...

I literally spent hours on this last night. I am gonna have to start a troubleshooting thread - keeps me from going crazy repeating steps, etc, and helps me work through the process.

Check PM

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0 volts on all. (mine's manual but key on, set to max, -0 v.)

All the tests for "coil not engaged" are done at the control head with a test light (auto & man).

Ck for a 09 code on the auto head.

The power to the connector on the compressor comes from the A/C Clutch Relay which is grounded by a signal from the ECM.
(There's also a signal with "A/C On" back to the ECM to adjust idle speed).

Humm, interesting.

Start the car and you should see alt. output (14.4 on mine) at the green wire on the connector (zero on the black cause it's ground). Shut the car off, key back to "On" and there's no voltage on the green wire.

Must be an ECM thing.

The above stuff was from the 8A section, Electrical Diagnosis.

There's also a/c clutch diagnosis in 6E3-C10

Don't forget the pressure switch cuts power to the compressor if pressures are out of range.

Where are you doing this? - "The coil is new, but even jumpering the wires with 12v I can't get the clutch to engage."

Thanks guys. More stuff to che k when i get home.

Andy - i applied battery voltage directly to the coil through a test light. I was trying to energize the coil to get it to engage the pulley.

I might disassemble the front again and bench test the coil. I emailed the company i bought it from and he said it bench tested good before he shipped it.

Checked my 89 with C68.
Key off= no power on green wire, or the black/white stripe wire.

Key on and set on 60* without engine running= no power on green wire, power on the black/white stripe wire.

Joel

I forgot to ask this, are you having problems with no voltage at the AC connector or is the clutch no pulling in?

If the clutch is noy "clicking" in, be sure the air gap is not too wide. About .010 - .011 is where it needs to be.
About the thickness of a buisness card.

Joel

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Matt, not sure how you applied the power thru a test light, but I know you know what you are doing. How about power thru the vehicle's wiring harness at the compressor/clutch?
Power and grounds both good there?

Thanks for all the help guys. I'm ashamed to say that my testing methods were a little flawed. My buddy has this sweet test light ($$$) that can also be used as a jumper wire. Mine can't...lol. I used my regular jumper wire and I was able to get the clutch to engage (btw, it's set at .5mm which is fsm settings).

I am still having problems getting it to engage by itself. I just hooked up the gages though and I'm gonna tinker a bit.

So here's something I don't quite understand yet. I decided to swap the blower control module just to see if it had any effect - here's what I found:

original bcm

Coil/compressor connector:

ign on / ac off
green wire .03 v
black/white wire 11.75 v

ign on / ac on auto
green wire 3.35 v
black/white wire 11.42 v

new bcm (slightly different, not as many prongs, but I guess this is how they come now?)

Coil/compressor connector:

ign on / ac off
green wire .03 v
black/white wire 11.56 v

ign on / ac on auto
green wire .03 v
black/white wire 11.26 v

(ps the minor voltage drops between tests were due to battery drain, left the door open...)


Notice the difference in the green wire values with the different bcm and ac on? Why I am getting 3.35 volts on that wire? I wonder if something is backfeeding??? I can't imagine that is correct.

Next step:

Hooked up the gauges and it's about 85-90 degrees in the garage. Static line pressure was low side (blue) 90 psi and high side (red) 80 psi.

I hooked the original bcm back up and started the car. Still no clutch engagement (there was none with either, btw).

I started the car and disconnected the compressor connector. I manually turned the coil on with the jumper wire (engaged clutch) and watched the pressures change. Low side was around 30ish and high side was climbing fast until I pulled the power at 350 psi. Let it settle down and tried again, same results. High side line was super hot at this point.

I then reconnected the compressor connector and with car running and ac set to auto tried jumpering the pressure cycling switch, clutch did not engage. I tried jumpering the high pressure cut off switch, clutch did not engage.

With my high pressure I am thinking the system is overcharged. We did vacuum it, but we had trouble with it. My neighbor was trying to use a micron gauge or something like that as they do in commercial refrigerant. Not sure if the vacuum was pulled correctly or if his gauges allowed it to be pulled right (kind of jerry-rigged). I now have a good matco set of r134a gauges to use. I think I need to evacuate the system, pull it down again, and recharge one more time. I think that is a contributing factor here.

I don't know if I should do that first or try to troubleshoot any more of the clutch engagement issue.

Matthew

PS - I want to give a big thank you to Bob at Century Auto Air who has been super patient with me on this issue and has been helping me out via email even though I am ac incompetent. He should definitely be your first choice for any ac related purchases.

www.centuryautoair.com

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Well there is a diode in the connector but it's supposed to stay at 0.7 v with the clutch disengaged.

Stupid question: have you done the diagnosis charts exactly as they are in the FSM?

Unless an 89 is way different...lookin' at a wirig diagram, the BCM has nada to do with the clutch.

Again, have you checked the clutch relay, jumped it?

Bill -

Yes and no

I did some diagnosis steps yesterday in various stages. I need to go back and redo them all in a scientific fashion. Part of my problem was ASSUMING the clutch might be bad due to my improper testing.

I still think the system was vacuumed and filled improperly, though.

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Bill, I make no bones about it, I am an ac idiot. There is a clutch relay? Seriously, I didn't know that.

Hence, no I have not checked that. I checked the fuse and the ground. That's about it. Other than testing for voltage.

But I know that I'm getting power to the connector, just don't know how the ground signal interacts.

The realy should have a brown wire from the a/c fuse going to 2 sides of the relay, green wire (which will be hot ONLY when the relay is grounded by the ECM (done with the green white wire).

Check the a/c fuse too.

BTW, just to harass the hell out you, what are you doing using a test light for a jumper when $.20 worth of clips from Radio Shack and a piece of wire make a jumper. I'll mail you some clips if you need them.

Anyway, find the connector to the a/c relay, take a jumper and back probe the green/white wire (with the engine running), this should energise the relay and you shouls see 12-14.5 on the compressor connector wire (green).

You can backprobe with a jumper wire hooked to the metal point of the test light.

I have the clips and wire, Bill...lol.

I'll look for that relay, thanks.

There is no relay for the C68, only the C60.

Joel

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Thanks, Joel.

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OK, I went by the 92 FSM cause it's the earliest one I have.
They must have added on between between 1990 & 92 then, C68 does have one in a 92.

It is supprising that there isn't one though.

Been doing some more reading - The 89 (and I believe 85-89) systems do not have a relay with the C68. C60 (manual does). On the C68, the ground and power are sent through the blower control module.

I will be away for a couple days so no more time to test this stuff. I'll post more results when I get some time.

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Yea, that's what I read, kinda strange.
Then the output from the BCM to the clutch connector (green wire ? ) should be 12v or more.

As far as I can tell from reading there is constant power to the clutch with key on. With ac command signal from head unit (and proper signals....or lack of...from pressure switches) then a ground is triggered that energizes the coil.

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Makes sense, everything else is turned on by grounding.

Sorry about not checking for power to comp. with key on/AC off.
I'll do that Friday AM and let you know how mine reads.

Joel

OK, I checked mine for power to the AC clutch with key on: AC command set to off. There is power to the black/ white wire.

Joel

Thanks for the help, Joel.

Did some tests the other night from FSM and the wiring all looks good.

Took the car to my friend's shop today and used his a/c machine. We had to fix a pinched o-ring on the compressor manifold but other than that he was impressed with my work getting everything done. Sucked out the old gas, only 1 lb. He said maybe it was low, maybe it was the o-ring leaking although there was no dye under it. Didn't leak until we filled it until about 1.75 lbs. Compressor still didn't turn on. He tested the switches, said they are good. We are both speculating the blower control module is to blame at this point, based on testing. I'll have to get one and test that out.

Matthew

I have not personally verified this yet, however if you have to replace the bcm, I've come across these part numbers for a 4/2 prong bcm:

original 16061602 / superceded by 12484912 / ac delco 1572530

You might cross reference them with:

BUICK ELECTRA (1985 - 1990)
BUICK ESTATE WAGON 1989
BUICK LESABRE (1986 - 1991)
BUICK PARK AVENUE (1991 - 1993)
BUICK REATTA (1988 - 1991)
BUICK RIVIERA (1986 - 1991)
CADILLAC 60 SPECIAL 1993
CADILLAC ALLANTE (1987 - 1991)
CADILLAC COMMERCIAL CHASSIS 1992
CADILLAC DEVILLE (1985 - 1993)
CADILLAC ELDORADO (1986 - 1991)
CADILLAC FLEETWOOD (1985 - 1992)
CADILLAC SEVILLE (1986 - 1991)
CHEVROLET CORVETTE (1986 - 1989)
OLDSMOBILE 98 REGENCY (1986 - 1993)
OLDSMOBILE 98 REGENCY BROUGHAM (1986 - 1990)
OLDSMOBILE 98 REGENCY ELITE (1991 - 1993)
OLDSMOBILE 98 REGENCY TOURING (1988 - 1993)
OLDSMOBILE DELTA 88 ROYALE (1986 - 1991)
OLDSMOBILE DELTA 88 ROYALE BROUGHAM (1986 - 1991)
OLDSMOBILE TORONADO (1987 - 1991)
OLDSMOBILE TORONADO BROUGHAM (1986 - 1987)
OLDSMOBILE TORONADO TROFEO (1988 - 1991)
PONTIAC BONNEVILLE LE (1988 - 1991)
PONTIAC BONNEVILLE SE (1988 - 1991)
PONTIAC BONNEVILLE SSE (1988 - 1991)

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Joel's getting key on power to the black/white, seems to me that if you were to back probe the other wire and ground it, the compressor should engege.

I can get the compressor to engage manually by providing power and ground. The issue is there is no ground signal from the bcm, which indicates to me it's bad. Might have overheated or received some feedback when the last coil fried.

Also, the bcm I used before to double check was not a 4/2 prong, it was a 3/1 prong like the newer style c4s had. It appears that is missing part of the circuit to complete the compressor signals so that portion of my testing was useless.

Quick update on this. I stopped at the u-pull yard today and actually found a bcm in an old Cadillac. Amazing. Only cost about $18 out the door. I was happy. Came home, put it in, still wouldn't fire the a/c clutch. Darn it. So I tested the system anyway since I have the gauges there. When manually engaging the compressor (fan switch disconnected so it runs) I was getting pressures on the low side in the 20s and on the high side around 225. I'm happy with that. So that tells me that system is charged correctly and there are no obstructions internally.

Got a chance this evening to do some real troubleshooting, what I should have done in the first place. It's a pia, though, since you have to pull the dash panels apart. Coincidentally, since my car is in a constant state of repair, I just leave all the screws out of the console and dash, etc so it takes all of 30 seconds to get to the heater control head. I swapped that out with a spare I have just to double check, that was not the issue.

So here is goes:

Isolation test 1:
Pressure cycling switch should ohm less than .5 ohms, passed.
(says to check refrigerant charge, as well, which I already know is good from above)

Isolation test 2:
BCM disconnected / ign switch run / a/c auto 65* / outside above 60*
-A (dk grn) connector C1 to ground should be battery / pass
-C (dk gn/yel) C2 to grd greater than 10 v / pass

Isolation test 3:
Fused jumper at BCM C1 / ign run
-A (dk gn) to ground - clutch engages / pass

Test A: Heater controls (I tried these tests with both head units and both blower control modules with almost identical results)

Testing wires at a/c head unit behind dash
ign run / ac auto 65* / outside above 60*

-C1 (lt grn) and ground s/b less than .5 volts - actual .05 v / pass
-C6 (dk blu/whi) and ground s/b greater than 6 v - actual 5.88-5.92 v (FAIL?)
-C3 (dk grn/or) and ground s/b 4-6 v - actual 6.06/6.3/6.98/7.24 depending on head unit/bcm combo (FAIL)
-change a/c mode to econ
C3 (dk gn/or) and ground s/b less than 1v - actual .06 v / pass

It appears it did not pass two parts.

Diagnosis:

1) Check the lt grn 66 wire and the black 904 wire for an open. If wires are good, check the a/c high pressure cutout switch and pressure cycling switch are closed. If the a/c high pressure cutout switch is open, replace it. If the pressure cycling switch is open, refer to section 1b for normal refrigerant level. If refrigerant level is normal, replace cycling switch.

Since I passed the first part, I am assuming the switches are good. But I have no way of testing the high pressure cutout switch that I know of. Pressure cycling switch passed the ohm test in isolation test 1. Any ideas on testing the high pressure cutout switch? I know I can jumper it when trying to run the system, but I mean an actual systematic ohm or voltage/load test.

2) Check for a short to ground in the dk blu/wht 997 wire. If the wire is good, refer to section 6E (wiring harnesses, etc).

I was close on this one. I think the bcm could be causing it to be slightly off. Perhaps some corrosion? I don't think there is a ground/short issue.

3) Remove bcm connector C2. Repeat the measurement at C3 (dk grn). If the voltage does not chance, check the dk grn 959 wire for a short to ground. If ok, replace the heater and a/c control assembly. If the voltage increases to 10 v or greater, replace the bcm.

I did this test and the voltage rose to around 12.22-12.27 for both bcm/head units. So I obviously have TWO bad blower control modules. My original and the junk yard replacement.

4) Replace the heater and a/c control assembly.

I passed this test, so this does not apply.

Sooooooo...

I'm gonna look for another blower control module tomorrow at another yard. If no luck, I'll buy a new one for $100. I'll keep updates going as I get the parts and testing done.

Well, I've got great news. I picked up another used bcm at a different scrap yard - $10 out the door. Popped it in and tested it, the clutch engaged as it should. I ran the a/c system and high side started climbing, fan wasn't kicking on as it should. So I disconnected the switch to engage the fan and ran the motor at 1500 rpm. Low side around 24, high side around 250+, climbing slowly after the car was sitting and running. Vent temps were around 52* from the center vent. I'm happy with that. I'm sure I can get them lower, too. I need to reinsulate the ducts and around the evaporator.

Does anyone know what the black gummy stuff is that is packed in around the evaporator lines? It's used on house a/c stuff, too. I just don't know the name. I need to replace that on the evaporator box.

A new fan switch and I've got fully functioning a/c!

Matthew

I think the sealant is gm strip caulk:

https://www.paragoncorvette.com/p-357482-3m-strip-caulk.aspx

Local dealer didn't have the fan switch in stock, said it's discontinued, and wanted $46 for it. I just bought it off Amazon shipped for $24.63...several bucks cheaper than my favorite site rockauto. Should be here in a couple days and I'm back in business.

Matthew

PS - fan switch # is 14078970 ac delco 15-2351

Congrats. Any AC shop would have that sealant. I think it comes as a tape with silver/metal peel off backing.

Your determination has paid off. How are you with hot tubs? Plenty of room for testing in those.

Good news! A piece of cake, right?

Joel

The only thing I can say is that I'm glad it's over??? Actually, I know a LOT more about a/c than I did before I started. So all in all it's not so bad.