Help! Is this normal? Electrical short?
Thread Starter
Joined: Jun 2008
Posts: 841
Likes: 7
From: South Pasadena, CA
Help! Is this normal? Electrical short? I pulled the engine/subframe from my car along with the battery and power cables. I was checking some circuits with a volt/ohm meter, and all positive contact points on the chassis ohm out to zero with ground!
Is this normal for no power cables/battery/alternator/starter/engine in the car? Or is the positive circuit shorted to ground somewhere?
I rewired the computer to the later model ECU, so am hoping it is not that. I really quadruple-checked everything there though, so I would be very surprised if the harness was the issue.
If someone also has the motor out and wants to check for me, just turn your volt/ohm meter to measure resistance Ω at say 20K ohms. Touch one probe to a positive contact like the underhood remote jumping point and the other probe to ground. Make sure the connection is good. 1 is infinite resistance, 0 (or close) is a closed circuit. You can also try something simple, like the 12v outlet. Thanks in advance for the assistance.
Is this normal for no power cables/battery/alternator/starter/engine in the car? Or is the positive circuit shorted to ground somewhere?
I rewired the computer to the later model ECU, so am hoping it is not that. I really quadruple-checked everything there though, so I would be very surprised if the harness was the issue.
If someone also has the motor out and wants to check for me, just turn your volt/ohm meter to measure resistance Ω at say 20K ohms. Touch one probe to a positive contact like the underhood remote jumping point and the other probe to ground. Make sure the connection is good. 1 is infinite resistance, 0 (or close) is a closed circuit. You can also try something simple, like the 12v outlet. Thanks in advance for the assistance.
You measure ohms in wires on one side of a circuit or another - not through a complete circuit back to ground.
The ohmmeter uses a current to measure resistance and when you try to flow that current backwards in a circuit (to ground) it will hit diodes and the path gets cut off. (So your measurement will look like you have the leads hooked up to nothing.)
^ This is a bad habit to get in to. If you try this with sensitive electronics, the current from the ohmmeter can do damage. Your car should be fine... but you shouldn't do this.
Thread Starter
Joined: Jun 2008
Posts: 841
Likes: 7
From: South Pasadena, CA
Thanks, I was freaking out a little bit there. Thinking that if I put the battery back later, that it will have a short and could fry the electronics or start a fire. I expected that the positive node would not trace back to ground so easily, but I guess there are many paths, such as current to supply the radio and alarm even when the car is off, so this is enough, let alone all of the complex diodes and resistors elsewhere.
Since there is no power, I was trying to determine which cables were hot, and which were grounded, but since both trace back to ground and positive, this method tells me nothing. I got the rest of it figured out for now (changing wiring to a manual from an auto), although I will have to eventually trace an ignition-powered source for my electric water pump. I will probably wait until the engine is back in though, as I won't know how long to make the wires anyway.
Thanks again.
Since there is no power, I was trying to determine which cables were hot, and which were grounded, but since both trace back to ground and positive, this method tells me nothing. I got the rest of it figured out for now (changing wiring to a manual from an auto), although I will have to eventually trace an ignition-powered source for my electric water pump. I will probably wait until the engine is back in though, as I won't know how long to make the wires anyway.
Thanks again.
I would not do this job without the three book set of GM Factory Service Manuals.
I think most of your years manuals are no longer carried by the original publisher, Helm Inc. but you can often find them on eBay.
You can also register on AutoZone.com and get access to most of the wiring schematics from those manuals. However; the Factory Service Manuals are much more extensive, have narrative descriptions, decoders, wiring guides, etc.
I think most of your years manuals are no longer carried by the original publisher, Helm Inc. but you can often find them on eBay.
You can also register on AutoZone.com and get access to most of the wiring schematics from those manuals. However; the Factory Service Manuals are much more extensive, have narrative descriptions, decoders, wiring guides, etc.
