Mechanics

CHEVY LOSS OF ALL ELECTRICAL POWER

1987 Chevrolet Corvette

Electrical problem
1987 Chevy Corvette V8 Two Wheel Drive Automatic 60,000 miles

The problem occurred when I accidentally did a double tap cranking the engine to start it. It has not run since then. When I turn the ignition key the dash lights all come on. Almost immediately, without getting to crank mode, all electrical power goes black. There is a noticeable click when this happens. The dash lights are out, the inside courtesy lights are out, the headlights are out, etc. After some period of time, the inside lights will once more come on when I open a door. Turning the ignition key, all goes black again with the click sound. The battery is charged and very new. I have a VOM if I need to do some trouble shooting.
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Frank Zeman
June 4, 2009.



Ok where are you hearing the noise from? Is it under the hood or behind the dash or? Let me know so I can look over the wiring diagram to try to help. Thanks.

Racefan966
Jun 4, 2009.
The click sounds like it is in the dash board area. I have the factory overhaul manual as well as the electrical manual for this model but have not spotted what or where it might be yet. It seems more around the driver side of the IP if that helps.
Could I have locked up a VATS relay that times back in? It is a real conundrum. Never heard that type of click in any vehicle ever before.

Tiny
Frank Zeman
Jun 4, 2009.
Ok under the dash there is a starter enable relay. This is hooked to the anti theft system if you car is equiped with one. It maybe that when you did that you caused a voltage drop or spike and the anti theft system saw this.
The audio alarm module is also under the dash. I have included a pic so you can see where these are at. I would like to do a starter enable relay test.
What you need to do find the relay it is just to right of the hazzard flasher. Once you locate it hook up your volt meter between term E and ground and then turn the key to the start position note the voltage. Now do the same between term C and ground also note voltage. It should be battery voltage on both tests. Now you need to build a fused jumper wire you put this between term E (yellow wire) and term A (dark green wire with white stripe) see if it cranks. If it cranks then you need to test the VATS decoder module next. Now you did test the battery to make sure it is good right? Get back to me with what you find and we will go from there.


http://www.2carpros.com/forum/automotive_pictures/249564_Graphic_89.jpg


Racefan966
Jun 5, 2009.
1. Terminal E to ground on the starter enable relay plug when the ignition key was turned on was zero volts.
2. Terminal C to ground, same as #1, zero voltage.
3. Fused jumper of E to A had no effect. No cranking.
4. There was no power showing during this test re inside lights or dash lights. That was before the test and during the test. Battery check shows 12 volts. This vehicle has the factory VATS system.
5. The starter enable plug and relay have some sort of dark brown goo on the contact surfaces. I presume this is to prevent corrosion of the connections and was put on at the factory. Noone had unplugged that puppy before me, I am sure.

Tiny
Frank Zeman
Jun 5, 2009.
Ok the goo is for anti corrosion. Now I need you to check one more thing here we are not going to test the decoder module. All these tests are done with the key in run position exept the last one it is done with key in the start position ok. Between term S (pink wire with black stripe) and ground with the volt meter should be battery voltage. Now check between term S again and Term L (black wire) should be battery voltage. Between term P (dark blue wire) and term L (black wire) should be 5 volts. Now the last test here is done with the key in start position. Between term V (dark green wire) and ground should be battery voltage. Let me know what you find here and we will go to the next step.

Racefan966
Jun 6, 2009.
I need the relay or connector I.D. Is it the Harness Connector Faces which go from A to P? Or is it the Heater & A/C Programer which goes from L to W? I see the Harness Connector under the driver side dash board. Cannot locate the Heater & A/C connection. It is listed as C-68 but I don't see it in any layout pics. If that is the one I need, I need its hiding place.
I have the instrument panel out and disconnected. Will this adversely effect the test or should I put that back first?
So far so good. I mentioned your web site to a neighbor with a 90+or- year vette with some sort of problems. Not sure about the exact age of his. Got another neighbor I intend to recommend your site also. Glad I found you folks!

Tiny
Frank Zeman
Jun 6, 2009.
What do you mean ac or heater programmer? I need you to test the decoder module for the key. Get back to me.

Racefan966
Jun 8, 2009.
The last message you sent you asked me to check voltages between S and Ground, S and L, P and L, and V and ground. I went to the Chevy electrical manual for this car. There were two plugs with letters corresponding to these. One was labeled as the Harness Connector Faces, it was found under the driver side instrument panel. The other was labeled Heater & A/C Programer. I could not find a location for it.
The latter one seemed to have all of the letters you asked me to check. It was I.D.'D in the manual as C-68 which referred to the location drawings for various plugs. I scanned all the drawings but failed to find this electrical connection plug. So I have not run this last series of checks yet.
The manual I am looking at is the 1987 Corvette " Electrical Diagnosis Service Manual Supplement.
I assumed I would have to break that plug apart to get the voltage readings.

Tiny
Frank Zeman
Jun 8, 2009.
It is part of the body control module sorry it didn't say that I had to look over the wiring diagram for the starter. Ok lets look at this again. Check fuse 14 it is a 10 amp then check maxi fuse number 50 it should be a 60 amp. There is a red wire that goes to the theft deterant relay make sure it has power. Also make sure that the purple wire at the starter has power when you put the key in the start possition. Now at the neutral saftey switch there is a yellow wire coming out of it going to the theft deterant relay make sure there is power here when the key is on. Now out of the theft deterant relay there is a yellow wire with a black stripe make sure this has power, this wire goes to the body control module to allow the starter to work. Finally make sure that the battery wire at the start has a constant 12 or battery voltage. Let me kwow what you find here.

Racefan966
Jun 9, 2009.
None of my fuses are marked numerically. They are marked with functions like wsw for windshield wiper. I checked all the 10 amp fuses and they were all OK. The largest fuses were 30 amp. Which were OK. These were in the fuse panel at the passenger end of the IP. There is an auxillary fuse panel in the center of the IP. I see no other fuses. The battery is showing 12 volts. Should I be testing power at the fuse boxes?
I have nothing marked Theft Detterent, but I do have a factory installed VATS system.
After a fairly long time the inside lights will function but as soon as I turn the ignition key they go out. This has happened several times.

Tiny
Frank Zeman
Jun 10, 2009.
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