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Topic: testing for battery drain or electrical short

in Forum: C3 Electrical

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testing for battery drain or electrical short (1/9)
12/5/14 11:56pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

Okay, is this correct way to check for battery drain or electrical short.

You take the negative side of your battery and remove the cable. You take a text light and hook it to the negative side that you removed the cable from, and then run the text light pin connection to the cable you just removed. If the test light is on than you have a direct short somewhere and thus a drain on your battery.

The light shows bright, and I have taken the fuses out. Disconnected the override switch, took the dash out and disconnected the ignition switch, light switch and all bulbs and gauge connections. Also the radio and cig. lighter. Amp and fuel gauge everything I could think of and I still have a drain on the battery.

If I disconnect the hot wires to the horn relay than the test light will cut off along with everything else in the system. Which is understandable because it comes off the hot wire of the starter that is fed from the battery.

Any suggestions on why I have this battery drain?

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Re: testing for battery drain or electrical short (2/9)
12/6/14 2:09pm

F4Gary

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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 1409

What do you mean by override switch?

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Re: testing for battery drain or electrical short (3/9)
12/6/14 2:32pm

eldredjames

Lifetime Member
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Temple City, CA - USA

Vette(s):
1969 Daytona Yellow. 350 / Automatic.

Joined: 10/3/2010
Posts: 365

All I can come up with is the door ajar/courtesy lights that come on with the door open or maybe the glove box light in the middle compartment.

Jim

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Re: testing for battery drain or electrical short (4/9)
12/6/14 6:12pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

I started to take out the door switches since I had everything unplugged behind the dash and the battery was still showing a drain.

but I decided to unplug some things in the engine compartment. I unplugged the wiper door limit switch and the three wires going to the wiper motor and this did not change anything but when I unplugged the connection that supplies power to the wiper motor from the ignition switch and the wiper relay behind the tach, and the override switch the drain stopped. I had thought I checked all of this prior to tearing into the dash, but must had missed this connection.

Now i suppose that I have a faulty wiper motor that is causing a short somehow. The motor is not that old. And only a 68 wiper motor will work. The ignition and dash harness are new along with all the switches in the dash so I don't think that is the problem. But I guess it could be something in this area!!

I think I will put everything back together with velcro since I seem to have to tear into it so often!

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Re: testing for battery drain or electrical short (5/9)
12/7/14 1:26am

eldredjames

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Temple City, CA - USA

Vette(s):
1969 Daytona Yellow. 350 / Automatic.

Joined: 10/3/2010
Posts: 365

I found this on the 'net. Worth a try.

May 6th, 2012, 05:54 PM #2 Jim T_____

Re: 1968 Current Drain Problem

Paul I am long time owner of 1968 convertible, unplug the center "glove box " light. Mine has been disconnected for over thirty years. Next up is the windshield wiper switch. Start the car and turn on the windshield wipers, wet the windshield if you like, and let them do at least one swipe and using the windshield wiper switch turn off the windshield wipers. Now test for a current draw? Reason I mention the wiper switch is that if my wiper switch is " accidentally" turned on/off when the car is not running it will pull current until the car is started and the wiper switch is used to cycle the windshield wipers on/off. There is a inline plastic connection that is accessible from the jack storage area that I use to disable the glove box light from working.

Velcro .. Hmmm. I was thinking of fuses that glow when current is passing through them.

Jim

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Re: testing for battery drain or electrical short (6/9)
12/7/14 4:12pm

F4Gary

Gold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 1409

My parasitic draw was the glove box/center compartment light. All I had to do was bend the latch catch a little and it's fixed. I found it when I reconnected my battery cutoff on a dark day and saw light coming out from around the center compartment lid.

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Re: testing for battery drain or electrical short (7/9)
12/7/14 7:07pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

Thanks Jim, I ran a test on the wiper motor, they worked fine, I then let them park themselves and now all is fine.

I don't have my dash back in yet, whereas I could try it by the wiper switch with the ignition on etc. but using the diagram Willcox Corvette shows on testing the 68 wiper motor allowed me to park the motor and using your information from 2012 gave me the idea to try it.

It does work and no drain and at all anymore with the motor plugged in.

Thanks so much for everyones help.

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Re: testing for battery drain or electrical short (8/9)
12/7/14 8:52pm

eldredjames

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Temple City, CA - USA

Vette(s):
1969 Daytona Yellow. 350 / Automatic.

Joined: 10/3/2010
Posts: 365

Great!

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Re: testing for battery drain or electrical short (9/9)
12/8/14 1:53pm

manchestershark

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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.

Joined: 10/31/2007
Posts: 2387

KUDOS to the center console light. It has drained my system more than once. Adjusting the door/switch is all I needed to reconcile my dilema. Just make sure after you are in the console, remember to close it up all the way, or light will stay on.

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