1985 shuts off when AC turned on
Thread Starter
Drifting
Joined: Mar 2017
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From: Nashville TN
2017 C4 of Year Finalist
1985 shuts off when AC turned on
i just fixed AC with a new blower motor. Worked great for a few days, then today I turn it on while driving down the highway-instantly all electronics in the car shut down. Engine does as well. I turn off AC, and a few seconds later the electronics come back. I pop the clutch and I'm back running perfectly. Me being me, I test this by turning AC on again. Instantly it's like the car has 0 electricity. Radio, dash, everything dies along with engine. I've tried it while idling as well, same thing.
Compressor is original to car, as is the whole system except for blower motor. I checked other things but didn't replace anything else.
Any ideas where to start?
Compressor is original to car, as is the whole system except for blower motor. I checked other things but didn't replace anything else.
Any ideas where to start?
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Let me add that I did a check under the hood and nothing looked out of place-so it's not like the serpentine belt shredded or anything. I'm sure it's something electrical.
Melting Slicks
Joined: May 2014
Posts: 2,897
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From: New Port Richey FL
How is your Charging System, Can you put a Volt Meter across your Battery and see if it can't keep up with Demand A/C Systems have a good Draw between A/C Clutch and Fans
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Take the battery cables OFF the battery, and LOOK at them for corrosion or markings of incomplete contact. Don't fall for a "visual" as being enough.
I just went through this on my 85. It started fine, but ran like crap, inst cluster was all wonkey, things were really f-ed up. All it was, was a bad connection at the battery.
I just went through this on my 85. It started fine, but ran like crap, inst cluster was all wonkey, things were really f-ed up. All it was, was a bad connection at the battery.
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
So, an update. Battery cables are tight. I unplug the compressor, and left everything as it is supposed to be. I could flip the AC switch with no problem. The blower came on and everything. I am thinking there must be a bad short in the compressor? It is original to the car, and it looks pretty old and not in great shape. My current theory is that the compressor was hanging on by a thread, and when I got the system working and started using it, it just went out. Oddly, it did not blow a fuse?
anyone ever rebuild a compressor? How hard is it? I'd kind of like to keep the original one in the car, if I can. It might be silly, but I like keeping things original if I can.
anyone ever rebuild a compressor? How hard is it? I'd kind of like to keep the original one in the car, if I can. It might be silly, but I like keeping things original if I can.
Team Owner
Joined: Sep 2003
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Checking cables ..........
TIGHT ain't the issue! Condition of the cable(s) I'd think are the possible issues and MAYBE because most of the fusible-links on an '85 are from the starter I don't know but the condition/quality of the connection at the starter could be an issue. They certainly need confirmed.
You need to check the condition of the ring terminal and the strands in the boots, if original cables that can be difficult best I recall.
Is the compressor locked? Very likely it seems and if you mentioned "car stalled" when turned on maybe you'd have gotten a different response. You mentioned loss of all electrical so people reacted to that.
A compressor rebuild I'd think foolish. JoeC just recently(might have been months or years) did I believe a compressor for his '85. I'd think he'll be by soon. Months or years I consider RECENT!
TIGHT ain't the issue! Condition of the cable(s) I'd think are the possible issues and MAYBE because most of the fusible-links on an '85 are from the starter I don't know but the condition/quality of the connection at the starter could be an issue. They certainly need confirmed.
You need to check the condition of the ring terminal and the strands in the boots, if original cables that can be difficult best I recall.
Is the compressor locked? Very likely it seems and if you mentioned "car stalled" when turned on maybe you'd have gotten a different response. You mentioned loss of all electrical so people reacted to that.
A compressor rebuild I'd think foolish. JoeC just recently(might have been months or years) did I believe a compressor for his '85. I'd think he'll be by soon. Months or years I consider RECENT!
Last edited by WVZR-1; Jul 27, 2017 at 08:45 AM.
Race Director
Joined: Aug 2000
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- a rebuild on an original R4 compressor is, 
, foolish -- not worth the time, material, or effort - most likely the average guy does not have the proper tooling for a rebuild anyway, so a new AC Delco service replacement (w/ clutch) is the only way to fly. $167 from rock auto. coming up on 6K miles since install -- ice cold, and no issues. I guarantee you, you'll have $167 in headaches, and unless you're experienced at rebuilds, no guarantee the thing will work when you're done. you could be opening a can of worms - 
http://www.rockauto.com/en/moreinfo....041208&jsn=486
as far as originality, remember, the world only needs so many museum pieces....
Last edited by Joe C; Jul 27, 2017 at 09:10 AM.
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Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Checking cables ..........
TIGHT ain't the issue! Condition of the cable(s) I'd think are the possible issues and MAYBE because most of the fusible-links on an '85 are from the starter I don't know but the condition/quality of the connection at the starter could be an issue. They certainly need confirmed.
You need to check the condition of the ring terminal and the strands in the boots, if original cables that can be difficult best I recall.
Is the compressor locked? Very likely it seems and if you mentioned "car stalled" when turned on maybe you'd have gotten a different response. You mentioned loss of all electrical so people reacted to that.
A compressor rebuild I'd think foolish. JoeC just recently(might have been months or years) did I believe a compressor for his '85. I'd think he'll be by soon. Months or years I consider RECENT!
TIGHT ain't the issue! Condition of the cable(s) I'd think are the possible issues and MAYBE because most of the fusible-links on an '85 are from the starter I don't know but the condition/quality of the connection at the starter could be an issue. They certainly need confirmed.
You need to check the condition of the ring terminal and the strands in the boots, if original cables that can be difficult best I recall.
Is the compressor locked? Very likely it seems and if you mentioned "car stalled" when turned on maybe you'd have gotten a different response. You mentioned loss of all electrical so people reacted to that.
A compressor rebuild I'd think foolish. JoeC just recently(might have been months or years) did I believe a compressor for his '85. I'd think he'll be by soon. Months or years I consider RECENT!
Joe C, thanks for the input! Sounds like a new one is in order-that price doesn't sound too bad at all.
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
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From: Nashville TN
2017 C4 of Year Finalist
One more thing-any way to PROVE that the compressor is bad, other than running the system with it unplugged? Hate to shell out cash for something I'm not 100% sure is bad, although I think the evidence is pretty strong at this point.
Burning Brakes
Joined: Jul 2010
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From: When Democracy becomes tyranny, the armed citizens will still get to vote!
Does the compressor still turn if you put a socket on the front nut where the clutch is? If it truly is an electrical only issue, it will be with the clutch not the compressor itself.
Burning Brakes
Joined: Nov 2016
Posts: 761
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From: Buchanan GA
Measure the resistance on the AC clutch coil. Should be somewhere in the 2ohm to 5ohm range IIRC. You could plug in something of equal resistance in the AC clutch plug and see what happens when you turn it on. This would complete the circuit and might help diagnose.
What happens if you turn the AC on when the engine isn't running but the key is in the run position? Could be a problem in the relay side of the circuit? Maybe someone can post a wiring diagram so we can trace it out?
What happens if you turn the AC on when the engine isn't running but the key is in the run position? Could be a problem in the relay side of the circuit? Maybe someone can post a wiring diagram so we can trace it out?
Zen Vet Master Level VII
Joined: Mar 2016
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From: Southlake, TX
1) you need to plug in your compressor and then turn the key forward without starting and see what happens
2) Unplug the compressor, turn the key forward without starting and see what happens.
3) you all ready know it will run without the AC and die with the AC.
If the electrical hold with the AC off and the key forward, you have isolated it to the AC electrical system. If, with the key forward non running and the AC on and everything blows up, you have a short/fault SOMETHING going on to the compressor.
Lets hope that the key forward and no AC, everything hold. Then get yourself a new compressor and brace for 100 degree days.
Last edited by billschroeder5842; Jul 27, 2017 at 04:41 PM.
Thread Starter
Drifting
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From: Nashville TN
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can you describe this procedure more? I'm not sure what you mean. I'm not terribly familiar with compressors
Thread Starter
Drifting
Joined: Mar 2017
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From: Nashville TN
2017 C4 of Year Finalist
Good point...
1) you need to plug in your compressor and then turn the key forward without starting and see what happens
2) Unplug the compressor, turn the key forward without starting and see what happens.
3) you all ready know it will run without the AC and die with the AC.
1) you need to plug in your compressor and then turn the key forward without starting and see what happens
2) Unplug the compressor, turn the key forward without starting and see what happens.
3) you all ready know it will run without the AC and die with the AC.
if I do the same thing, but with the compressor not plugged in, everything works OK. The blower motor comes on, but of course it only blows outside temperature air.
I will test the resistance of the compressor later. I don't have access to it at the moment.
Based on these tests, I am fairly certain that the compressor is at fault.
Burning Brakes
Joined: Jul 2010
Posts: 1,210
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From: When Democracy becomes tyranny, the armed citizens will still get to vote!
There are two parts to the compressor clutch. The outer part where the belt rides that spins when the engine is running. The inner part that houses the electromagnet that is bolted to the compressor shaft. When the clutch is energized, the inner and outer clutch pieces are coupled together allowing the belt to turn the compressor. If you look into the pocket in the front of the compressor clutch you will see the nut that holds the inner part of the clutch to the compressor shaft. If you put a wrench/socket on that and it spins freely, your compressor isn't locked up.
Also, I believe that you should have 12 vdc between the two contacts that plug into the compressor when the a/c is turned on. This should be checked as well.
Also, I believe that you should have 12 vdc between the two contacts that plug into the compressor when the a/c is turned on. This should be checked as well.
Zen Vet Master Level VII
Joined: Mar 2016
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From: Southlake, TX
With the compressor plugged in, and the engine not running, if I turn the key forward and then turn the AC on, the electrical still goes out.
if I do the same thing, but with the compressor not plugged in, everything works OK. The blower motor comes on, but of course it only blows outside temperature air.
if I do the same thing, but with the compressor not plugged in, everything works OK. The blower motor comes on, but of course it only blows outside temperature air.
1) Wiring worn and hitting metal (but probably not at it would blow a fuse)
2) Relay Stuck- Again a fuse would go
3) Compressor- The most likely culprit. Swap your system, do a 134 change if you have not done it already and enjoy.
Last edited by billschroeder5842; Jul 27, 2017 at 07:40 PM.
Thread Starter
Drifting
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From: Nashville TN
2017 C4 of Year Finalist
Thanks for all the replies! I will do some more checks soon and post results. Cadwiz I did not know that about the compressor. I’ll check to see if it’s locked up. Do I need to take off the belt to test that?
Bill-I’ve heard very mixed results from 134a swap. The higher pressures can blow old seals and hoses? Or is that just a story?
Anything tricky about swapping compressor? I assume I just vacuum the system, unbolt and swap, and refill? I’ve never done AC work before, love to learn but want to do it right.
Bill-I’ve heard very mixed results from 134a swap. The higher pressures can blow old seals and hoses? Or is that just a story?
Anything tricky about swapping compressor? I assume I just vacuum the system, unbolt and swap, and refill? I’ve never done AC work before, love to learn but want to do it right.
Race Director
Joined: Aug 2000
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Thanks for all the replies! I will do some more checks soon and post results. Cadwiz I did not know that about the compressor. I’ll check to see if it’s locked up. Do I need to take off the belt to test that?
Bill-I’ve heard very mixed results from 134a swap. The higher pressures can blow old seals and hoses? Or is that just a story?
Anything tricky about swapping compressor? I assume I just vacuum the system, unbolt and swap, and refill? I’ve never done AC work before, love to learn but want to do it right.
Bill-I’ve heard very mixed results from 134a swap. The higher pressures can blow old seals and hoses? Or is that just a story?
Anything tricky about swapping compressor? I assume I just vacuum the system, unbolt and swap, and refill? I’ve never done AC work before, love to learn but want to do it right.
-- if you're swapping out the compressor, might as well change out the accumulator/dryer. $20 for a delco service replacement. http://www.rockauto.com/en/moreinfo....041208&jsn=483. for a proper 134a conversion, you'll need a .067 orifice tube and a "retrofit" low cycling switch. good idea to solvent flush the remaining components. 134a typically uses PAG oil, however ester will work with both r12 and 134a. as far as swapping out the compressor itself, other than the magic bottom bolt, one of the mounting bolts goes in from the rear, which means you'll need to pull the RH valve cover. while you're at it, might as well do this little mod on the compressor mounting bracket - makes installation a snap. here's my thread on the whole compressor mounting bracket mod -- https://www.corvetteforum.com/forums...ification.html - some guys will say you can pull the compressor/compressor bracket forward to remove the rear mounted bolt, but it seem to me to be more work than pulling the VC. to each his own....
some guys have had success with the $39 conversion in a can method, but I did it by the book. cost me a few bucks, but that's the way I wanted to go. here's a thread on a 134a conversion -- https://www.corvetteforum.com/forums...requested.html
thread on the compressor mounting -- https://www.corvetteforum.com/forums...acket-fun.html
FWIW, my 134a conversion -- on a 90° day at crusin' speed, center duct temps around 40° now that's
hope this helps --
Last edited by Joe C; Jul 27, 2017 at 11:11 PM.