Need help locating electrical short please
Thread Starter
Racer
Joined: Jan 2003
Posts: 270
Likes: 0
From: Erie pa
Need help locating electrical short please
I have a 1980 vette. I inadvertantly shorted out some of the engine wiring harness hooking up the starter. I replaced just the burnt out wires and the car now starts and runs, and everything except the wipers seem to work. Now however, the battery in the car dies in a day or two. So I assume I have a short somewhere. Can someone help me locate it. I was told to pull one fuse at a time and see if one causes the battery to not die. That sounds good, but I would like to know if I could be more specific. I have a cheap meter, but I honestly don't know how to use it. I thought I would measure the battery, i am guessing it should be 12 volts charged, then pull a fuse and measure the battery again later on. Is this correct? What setting do I put the meter on, it has about 8 of them. I would appreciate any help with this.
Also can a drain on the battery, or a short cause the engine to run with less power?
Thanks,
Eric
Also can a drain on the battery, or a short cause the engine to run with less power?
Thanks,
Eric
Melting Slicks
Joined: May 2004
Posts: 2,510
Likes: 529
From: Willowbrook IL
St. Jude Donor '13-'14-'15-'16
Eric,
Disconnect the on lead of the battery and charge it
Take your digital multi-meter and set it to read AMPS not volts
Connect the test leads to the meter as described in the meter's instructions to read AMPS
Connect one meter lead to the battery, the other meter lead to the disconnected battery cable
Any reading of more that a few milli-amps is a short to ground
Remove one fuse at a time and monitor the meter, when the current drain goes to zero, that circuit has the short.
IF the meter still displays a drain (short) my best guess is that you now have a short to ground in the alternator, take it to your FALPS and have it tested.
Disconnect the on lead of the battery and charge it
Take your digital multi-meter and set it to read AMPS not volts
Connect the test leads to the meter as described in the meter's instructions to read AMPS
Connect one meter lead to the battery, the other meter lead to the disconnected battery cable
Any reading of more that a few milli-amps is a short to ground
Remove one fuse at a time and monitor the meter, when the current drain goes to zero, that circuit has the short.
IF the meter still displays a drain (short) my best guess is that you now have a short to ground in the alternator, take it to your FALPS and have it tested.
Race Director
Joined: Oct 2000
Posts: 11,891
Likes: 3
From: Kansas City, MO ...I'd like to go fishing and catch a fishstick. That'd be convenient. - Mitch Hedberg
Take a light bulb and hold it close to the wiring. Then move it around until it starts to light up. That's when you've found out where the electricity is escaping.
Seriously, I would focus on the area you damaged. When installing the starter wiring, did you accidentally cut through part or all of a section of the wiring harness? You say you replaced burned up wires which indicates more than accidentally slicing a couple wires. I'm assuming you checked all the fuses to make sure none were blown. If your problem area is the wipers, have you traces all of the wiring related to the wipers?
Which engine harness did you damage and physically where was it damaged? I can check my schematic for you or I can run down and have a look at mine since it's here at work today.
Seriously, I would focus on the area you damaged. When installing the starter wiring, did you accidentally cut through part or all of a section of the wiring harness? You say you replaced burned up wires which indicates more than accidentally slicing a couple wires. I'm assuming you checked all the fuses to make sure none were blown. If your problem area is the wipers, have you traces all of the wiring related to the wipers?
Which engine harness did you damage and physically where was it damaged? I can check my schematic for you or I can run down and have a look at mine since it's here at work today.
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
Remove one fuse at a time and monitor the meter, when the current drain goes to zero, that circuit has the short.
Just remember that the switch for the door is open so the courtesy lamp circut will show a short keep the door switch closed & the hood closed.
Just remember that the switch for the door is open so the courtesy lamp circut will show a short keep the door switch closed & the hood closed.
Thread Starter
Racer
Joined: Jan 2003
Posts: 270
Likes: 0
From: Erie pa
Thanks for all the help guys. I am going to read how to use the meter at lunch today, Friday, and start troubleshooting tonight or tomorrow.
The burned wires were in the engine harness and smoked wires all the way up to under the dash as well. I pulled the dash and swapped out all I could see that were burned.
Do I disconnect the positive or negative cable at the battery when I test, does it matter?
I will try to find the ground for the wipers to see if that solves the wiper problem.
Also, will a drain on the battery like this decrease my engine power in any way?
thanks,
eric
The burned wires were in the engine harness and smoked wires all the way up to under the dash as well. I pulled the dash and swapped out all I could see that were burned.
Do I disconnect the positive or negative cable at the battery when I test, does it matter?
I will try to find the ground for the wipers to see if that solves the wiper problem.
Also, will a drain on the battery like this decrease my engine power in any way?
thanks,
eric
Team Owner
Joined: Jul 2004
Posts: 40,412
Likes: 792
From: Redondo Beach, California
Originally Posted by G dad
Just remember that the switch for the door is open so the courtesy lamp circut will show a short keep the door switch closed & the hood closed.
Team Owner
Joined: Jul 2004
Posts: 40,412
Likes: 792
From: Redondo Beach, California
Also, after doing electrical work on the car, particularly when you've done some substantial mods, etc, you don't have to....and I don't think you should....power up the car with the big lead battery. If there's a short it can put out hundreds of amperes and really fry and vaporize things. Why not buy two 6 volt lantern batteries, wire them in series for 12 volts total, and then connect them to the cars electrical system? If there's a inadvertent short they won't put out as much current. (The best more expensive option is to use a current limited 12 volt power supply.)
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Burning Brakes
Joined: Feb 2005
Posts: 977
Likes: 1
From: wash. dc
i had a short that was driving me crazy too... bought multi meters and the whole nine... finally found out the pos cable from the battery had welded itself to the exhaust manifold...something you might wanna check
Team Owner
Joined: Jun 2001
Posts: 23,380
Likes: 1,067
From: Virginia USA
The ground for the wiper motor travels down the engine wiring harness to the starter side of the engine. It is usually connected to the blower motor ground point. To test you wipers and you think it is a wiper motor ground, all you have to do is take a piece of wire and ground the outside case of the motor to any grounded surface.
Thread Starter
Racer
Joined: Jan 2003
Posts: 270
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From: Erie pa
Well I tried to use the amps setting, but I think I have a cheap meter and it is giving me confusing results. I am going to try to get a better one from a friend tomorrow.
Grounding the wiper motor didn't get them going, So I will look elsewhere for the culprit.
Also, I noticed a lot of other unconnected wires I hadn't noticed before, and some of them were hot
. I am thinking if this doesn't work out, I may need a new wiring harness, not a job I want to do, but if I need to, where is a good supplier of harnesses for our cars?
I will continue working on this and keep you posted.
thanks,
Eric
Grounding the wiper motor didn't get them going, So I will look elsewhere for the culprit.
Also, I noticed a lot of other unconnected wires I hadn't noticed before, and some of them were hot
. I am thinking if this doesn't work out, I may need a new wiring harness, not a job I want to do, but if I need to, where is a good supplier of harnesses for our cars?I will continue working on this and keep you posted.
thanks,
Eric
Melting Slicks
Joined: Aug 2005
Posts: 2,560
Likes: 5
From: the land of a never ending frame-off resto-mod. May Visa have mercy on my soul.
If you need a new harness try these folks. http://www.lectriclimited.com/corvette_catalog.htm They carry a great selection and are pre tested.
Good luck DB
Good luck DB
Burning Brakes
Joined: Sep 2005
Posts: 1,078
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From: Santee CA
Just a thought:
If your battery is draining after a day or so, check your alternator and wiring to your alternator as well; the short might have extended out there and deep-fried it.
I actually had a similar problem in an old Saturn of mine; the alternator died and I drove my car down from Orange County to San Diego, running on nothing but my battery. Fortunately it was during the day, so I didn't need any power for my headlights or anything draining like that, but when I got there the car died in the driveway and required an overnight battery charge for me to get it into the dealer.
If your battery is draining after a day or so, check your alternator and wiring to your alternator as well; the short might have extended out there and deep-fried it.
I actually had a similar problem in an old Saturn of mine; the alternator died and I drove my car down from Orange County to San Diego, running on nothing but my battery. Fortunately it was during the day, so I didn't need any power for my headlights or anything draining like that, but when I got there the car died in the driveway and required an overnight battery charge for me to get it into the dealer.