70 LT1 Door Ajar electrical gremlin
I am finishing up the restoration of a 70 LT1 and am addressing some electrical gremlins. The courtesy light and horn buzzer system is fixed .Now I could use some help on the door ajar circuit. I installed new switches in each rear door jamb.Each had two wires and the installation went smoothly. The door ajar lamp is supposed to light when either or both doors are open and the ignition key is on. In that condition I get NO light until I pull on the light switch and then I get a continuous door ajar warning light regardless of door or key position.I have tested the newly installed door ajar switches and they are working properly. Any ideas as to what is wrong here? The car is a very original low mileage car that has not been monkeyed with. Thanks for any help. Bill Gould
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Re: 70 LT1 Door Ajar electrical gremlin
The door ajar plate is grounded and the wire may be broken off Test the plate for a ground.Lyle
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Re: 70 LT1 Door Ajar electrical gremlin
Just a thought:
These switches are self-adjusting - or at least the original ones were. That is the switch is installed with the center pin pulled all the way out, and as the door is closed for the first time the center pin is pushed into the outer sleeve the proper distance to fully contact the closed door. Be sure the switch is installed with the center pin all the way out. On some cars we see a rubber pad on the door that the switch contacts. We believe this pad is because the door is too thin where it contacts the switch and some "finessing" is needed. We don't see the pads on 1970 as much as 1971 and 1972, but if needed I doubt anyone could say "never".TerryComment
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Re: 70 LT1 Door Ajar electrical gremlin
Bill, if you can jump the two wires and the light lights than the circuit is good, are the switches GM original SX switches? or did you replace them? I can tell you I had no luck with the reproduction switches. the connection would not always happen.So I took the originals, and ended up taking some steel wool and cleaning the contact area were the pins seals.New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: 70 LT1 Door Ajar electrical gremlin
Gents, thanks for your speedy response.
Lyle, my 70 does not have a switch plate ground to my knowledge. The threaded steel backing plate is riveted onto fiberglass . The door ajar switch is a pass through switch. At least that is how I see it.
Ed, I jumped each door switch and it made no difference. I am certain that the repro switches i used are functioning correctly. I used a ball of dum dum to confirm that they are being activated with the door closed. I believe that the switchas are not the cause of my problem.
Terry, The switches are functioning as they should.
I do not understand the connection between my door ajar circuit and the main headlight switch but the only time the door ajar lamp is lit when I pull on the main headlight switch and then the light stays on independant of door position or key position. I am puzzled.Comment
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Re: 70 LT1 Door Ajar electrical gremlin
Yes the switch plate should be grounded. There is a wire attached for that purpose. Without that ground the switches will not work. That wire commonly becomes disconnected. I believe you can get access to it by removing the plate at the front of the rear wheel house. Four screws hole that plate on. That plate gives access to one of the body mounts and that ground wire.TerryComment
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Re: 70 LT1 Door Ajar electrical gremlin
That just may be the issue. I will pull the access cover and have a look for the ground wire. I had the covers off both sides when i installed the new switches because there was not enough wire installed at the factory to install new switches. I soldered 4 inches extra wire on each side so that I could thread the wires through the door jamb and install the tiny contacts. Hope that solves it and will let you know. Bill GouldComment
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Re: 70 LT1 Door Ajar electrical gremlin
Terry, should both sides have a ground wire from the riveted plate to ground or just one side? If that plate is grounded then when the door is open and the switch makes contact then both wires will short to ground?Comment
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Re: 70 LT1 Door Ajar electrical gremlin
Terry, I removed the inspection plates and I do not see how there could be a ground wire attached to the switch plate. That plate is riveted to the outer fiberglass but there is no access to it from the inside. The AIM at UPC 12 C4 shows a large rubber grommet which is present on both sides. That grommet goes through sheet metal as an insulator. There is noaccess to the riveted plate from the inside . It would be possible to have a third contact in the switch that could go to ground via another wire. I agree that could have been removed but I do not see anywhere that it would be attached to the sheet metal and there is not another wire coming from the harness. And the wiring diagrams on UPC 12 D7 and D8 show only two wires implying a pass through . No ground is shown on either switch. Can you describe the nature of the ground connection to the switch plate? I appreciate your help and that of others.Comment
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Re: 70 LT1 Door Ajar electrical gremlin
Bill, The plate is there to retain the switch, the black wire on switch is ground, as is the white. I think you need to find out where the black wire is grounded at. have you tried a jumper wire to ground and then ground to white wire?New England chapter member, 63 Convert. 327/340- Chapter/Regional/national Top Flight, 72 coupe- chapter and regional Top Flight.Comment
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Re: 70 LT1 Door Ajar electrical gremlin
Your switch should have three wires one is the ground. With two wires the plate needs grounded.I have got the plate out through the hole and fixed more than one time.Lyle
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Re: 70 LT1 Door Ajar electrical gremlin
Lyle, Are you sure that 70 has three wires? I think maybe later cars had
three wires on the door ajar switch and 70 had two. My car is unmolested and
there are only two wires coming into the area behind the switch, and the AIM
wiring diagram shows two wires.Comment
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Re: 70 LT1 Door Ajar electrical gremlin
3 wires stopped in Nov. 1972 I do not know what a 70 had. Have you checked behind the carpet to see if their is a ground wire on the bulkhead. See how many wires go out through the hole to the switchLyle
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Re: 70 LT1 Door Ajar electrical gremlin
Both sides should have the plate grounded. The way that works is there is 12volts to one side of the bulb when the ignition is on. The switch makes contact to ground when the door is not fully closed. That ground goes to the other side of the light bulb, and the bulb lights. The courtesy lights, under the dash and on the back wall of the luggage compartment, work the same way, but they work off the switch at the front of the door.TerryComment
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Re: 70 LT1 Door Ajar electrical gremlin
I know one wire was for the alarm in 73 so you only need two wires with no alarm. one is the ground the other lights the door adjar light.Lyle
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