Electrical Short - 75 Vette
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Electrical Short - 75 Vette
I have a electrical short. I do know that it is in the interior door lights / cig lighter fuse curcuit. I also think that the factory alarm is on this fuse. I can pull the fuse out and let the vette sit 2 weeks and the battery never runs down. I can put the fuse back in that the battery will run down in a couple of days. I was hopping that you guys might give me some tips or ideas where to look. I removed the wires from the key lock in the fender and taped them up and that didn't help. I also checked under the glove box, where the jack is located and there's notheng wrong there.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Electrical Short - 75 Vette (Paul 75 L82)
Paul, I don't have my book handy at the moment, but isn't the rear center comparment light also on the circuit? If so, the lid may be leaving the light on.
The alarm and the door ajar are also on there - yes.
Does the factory alarm work? Does it set or does it go off right away?
Are you sure the interior lights and the light behind in the cargo area go off when the door is closed?
The alarm and the door ajar are also on there - yes.
Does the factory alarm work? Does it set or does it go off right away?
Are you sure the interior lights and the light behind in the cargo area go off when the door is closed?
Safety Car
Joined: Jul 2002
Posts: 4,269
Likes: 3
From: St. Charles IL
Cruise-In 5-6-7-8-9-11-12 Veteran
A CI-6 Car Show Winner
Re: Electrical Short - 75 Vette (Paul 75 L82)
Good suggestion about interior lights and glove box light. The headlamp warning switches are also on this circuit. I would suggest pulling all the fuses except the fuse for the lighter and interior lights. Connect a voltmeter between the battery plus terminal and the wire that was on plus (must be removed) then disconnect each component on at a time until you have no reading on the voltmeter. You could also make a light to test from a spare light socket and 12 volt light, it should glow something less then full brightness and then turn off once you find your short.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Re: Electrical Short - 75 Vette (Big Fish)
You have an electrical draw, not a short. If you had a short, it would either pop a fuse or burn up. THE most common causes of battery drain in those cars are the interior light delay module, or a bad diode in the alternator.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Electrical Short - 75 Vette (wombvette)
No delay module for '75.
Here's what's on that circuit: clock, lighter, courtesy, antitheft alarm, glove box.
This includes the pin switch on the cowl for hood alarm and the 2 pin switches for each door. The front door jam switch is the interior lights and the rear switch is for the door ajar indicator and alarm.
[Modified by KenSny, 9:45 AM 11/5/2003]
Here's what's on that circuit: clock, lighter, courtesy, antitheft alarm, glove box.
This includes the pin switch on the cowl for hood alarm and the 2 pin switches for each door. The front door jam switch is the interior lights and the rear switch is for the door ajar indicator and alarm.
[Modified by KenSny, 9:45 AM 11/5/2003]
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Electrical Short - 75 Vette (KenSny)
I would like to completly disconnect the factory alarm. I took the two wires off of the key lock on the fender and taped them up. Does that power wire go straight to the fuse box. By removing these two wires can I say that the alarm is disconnected? The interior lights work good. They all work and they all go off when the door is shut. Any ideas on where to look next? There's no reason to pull all of the fuses. The drain is in this curcuit.
Drifting
Joined: Dec 2002
Posts: 1,887
Likes: 1
From: Hill AFB area Utah
Re: Electrical Short - 75 Vette (Paul 75 L82)
Here is what I found on my 75 vette. same thing happened to mine. I found that the alarm system had been tripped however the horn was shorted so it didn't sound. it would always drain the battery. after I replaced the horn and turned the key switch to the off position it never happened again. the side benifit is now the alarm work perfectly !
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Electrical Short - 75 Vette (dmrodco)
I thought that the alarm was the problem. I didn't work anyway as the relay was bad. I just don't know if removing the wires from the fender switch and taping them up disconnected the alarm. If it did then my problem id somewhere else in that curcuit. Does someone have a wiring dirgram for this curcuit for a 75? My two manuals don't even show the alarm wiring.
[Modified by Paul 75 L82, 12:53 PM 11/5/2003]
[Modified by Paul 75 L82, 12:53 PM 11/5/2003]
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Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Electrical Short - 75 Vette (Paul 75 L82)
Paul, you really need to get a wiring diagram. Get the laminated one (easy to use crayons to trace stuff) from 'Lectric Limited for about $10.
I wrote an article here on how to troubleshoot the alarm system. But, the pin switches at the rear of the door jam are dual function. They power the door ajar indicator as well as the alarm.
What connector did you pull from the rear of the alarm switch. Did it have a rubber boot that went to a black switch behind the key switch? If so then that is not really the alarm switch, merely the anti-tampering switch.
I think your problem is that something is "on". Did you check the center storage box light? How about the lighter - does the battery run down without the lighter in the holder?
You really need to start isolating all the other items.
And I agree, there is no need at this time to pull all the other fuses if you are sure that the problem goes away when you have this fuse removed.
[Modified by KenSny, 1:10 PM 11/5/2003]
I wrote an article here on how to troubleshoot the alarm system. But, the pin switches at the rear of the door jam are dual function. They power the door ajar indicator as well as the alarm.
What connector did you pull from the rear of the alarm switch. Did it have a rubber boot that went to a black switch behind the key switch? If so then that is not really the alarm switch, merely the anti-tampering switch.
I think your problem is that something is "on". Did you check the center storage box light? How about the lighter - does the battery run down without the lighter in the holder?
You really need to start isolating all the other items.
And I agree, there is no need at this time to pull all the other fuses if you are sure that the problem goes away when you have this fuse removed.
[Modified by KenSny, 1:10 PM 11/5/2003]
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Electrical Short - 75 Vette (KenSny)
KenSny - I only removed the two wires that goes to the key switch on the fender. I taped up both ends of the wires. I think your right about something being on and I don't know it. What black connector are you talking about?
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Electrical Short - 75 Vette (Paul 75 L82)
There should be a black and a yellow wire going into a rubber boot that connects to a plastic switch that mounts behind the key switch. Usually this switch is missing and the wires are pushed out of the way. If you find them make sure someone has not connected the two together as this will run the alarm all the time and if your alarm horn is NG then you'd never know.
The glove box light switch is usually not closing all the way and causing the light to stay on. You'll never know because the lid is closed. Try removing the bulb.
I have seen cig lighters go bad, not often, but sometimes they stick in the down position just enough to draw some current but if the lighter is not warm to the touch then it's probably OK.
If it was me, I'd try removing the 4 door pin switches one-at-a-time until I isolated which part of the circuit was causing a problem. Does your door ajar light come on with the doors open? Does it go out with them closed? Do you all the interior light work correctly? Does the clock work?
The glove box light switch is usually not closing all the way and causing the light to stay on. You'll never know because the lid is closed. Try removing the bulb.
I have seen cig lighters go bad, not often, but sometimes they stick in the down position just enough to draw some current but if the lighter is not warm to the touch then it's probably OK.
If it was me, I'd try removing the 4 door pin switches one-at-a-time until I isolated which part of the circuit was causing a problem. Does your door ajar light come on with the doors open? Does it go out with them closed? Do you all the interior light work correctly? Does the clock work?
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Electrical Short - 75 Vette (KenSny)
Thanks Ken, I think the alarm is disconnected. I would like to have a wiring diagram for the alarm. Glove box light has been disconnected and wires taped up. Cig could be a problem, seams like I remember that I thought it felt warm. I will disconnect it and if that's not it I will start with the door switches. Thanks for your help. I won't be able to work on the vette till this week-end and then I will need to watch the voltage drain for a couple of days. Will get a hold of you next week with the outcome.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Electrical Short - 75 Vette (Paul 75 L82)
My wife's car is a Jeep and she leaves the cell phone plugged in all the time. The cig lighter does not work when the ignition is off and the phone turns off when the power is gone so all is ok.
In my Beretta the lighter still has power with the ignition off. So my wife borrows my car for a week while I do some work on the Jeep and use it to haul some stuff around.
The battery in the Beretta went dead in about 5 days from her leaving the cell phone plugged in! Sometimes the simple things bite you in the butt.
Now I'm real careful about leaving the cell phone in the Corvette as well.....
I made up a drawing for the alarm wiring just by following the GM layout. I have no way to send it to you or I would. Look for my post on the alarm or I can email you an updated version in text format.
In my Beretta the lighter still has power with the ignition off. So my wife borrows my car for a week while I do some work on the Jeep and use it to haul some stuff around.
The battery in the Beretta went dead in about 5 days from her leaving the cell phone plugged in! Sometimes the simple things bite you in the butt.
Now I'm real careful about leaving the cell phone in the Corvette as well.....
I made up a drawing for the alarm wiring just by following the GM layout. I have no way to send it to you or I would. Look for my post on the alarm or I can email you an updated version in text format.
