Interesting Electrical Problem
Thread Starter
Racer
Joined: Jan 2006
Posts: 381
Likes: 24
From: Uxbridge Ontario
Interesting Electrical Problem
I am at my end in trying to figure it out. I have a 71 with Air, and if I leave the plug in the AC compressor in various points on the fan switch I cannot turn off the engine. If I pull the plug then the ignition switch acts normally. I have checked each one of the electical connects to make sure they are connected to the right thing and the right way. I think it must be one of the relays. The cost of replacing the relays or switchs is not high but I just don't want to replace stuff just for replacing them. Help would be appreciated.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Interesting. There is a relay on the left side of the engine bay firewall which has something to do with activating the compressor clutch for 3seconds after switching off the engine. The extra load on the engine was supposed to help prevent "engine dieseling" [engine run-on]. Maybe there is some failure mode within that device that is allowing power to continue flowing to the ignition. These relays were only on C3's for 2 years, I believe; so there is little information on them. You can't buy aftermarket replacements, but you might be able to find one in a Corvette salvage yard, if that is your problem.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,027
I am at my end in trying to figure it out. I have a 71 with Air, and if I leave the plug in the AC compressor in various points on the fan switch I cannot turn off the engine. If I pull the plug then the ignition switch acts normally. I have checked each one of the electical connects to make sure they are connected to the right thing and the right way. I think it must be one of the relays. The cost of replacing the relays or switchs is not high but I just don't want to replace stuff just for replacing them. Help would be appreciated.
You get problem of the year.
Wish I had a 71 schematic.
Thread Starter
Racer
Joined: Jan 2006
Posts: 381
Likes: 24
From: Uxbridge Ontario
Sixfooter you have it right. The maint book doesn't show you how to diagnoise the relay on the firewall nor the anti-dieseling switch in the dash. I guess all I am left with us replacing the relays. Thanks guys for her help. I will let you know what I find.
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Thread Starter
Racer
Joined: Jan 2006
Posts: 381
Likes: 24
From: Uxbridge Ontario
So still can't figure this thing out, I replaced the relay on the Evaporatory and same problem. Strange I only have 1 relay on the inside of the car which is mounted on the heater/cooler box, the maint book and the build book show two relays. Did some further testing and found if I have everything hooked up and I turn the control to the ACX setting the car will not turn off, if I have the control on the heat setting then I need to have the fan switch on the first position if it is in the off position the car will not turn off. Yes, I checked the fan switch to make sure the replacement is the right one for cars with AC. This may mean a trip to the repair shop. Some how it is supplying voltage to the coil that is why things won't turn off. Any further suggestions?
Instructor
Joined: Jan 2007
Posts: 152
Likes: 0
another long shot
This is another long shot, but who knows?
Has the dash and/or center console been removed and or replaced? There may be a Hot/Ground wire pinched together that is sending voltage back through the ground circuit, just enough to keep the coil alive.
What was the history of events before this problem started? Did you have anything apart, replaced, take the car to the shop, etc... ?
Has the dash and/or center console been removed and or replaced? There may be a Hot/Ground wire pinched together that is sending voltage back through the ground circuit, just enough to keep the coil alive.
What was the history of events before this problem started? Did you have anything apart, replaced, take the car to the shop, etc... ?
