12 volt Reading always when key off
Thread Starter
Pro
Joined: Nov 2014
Posts: 503
Likes: 66
From: Florida
12 volt Reading always when key off
While working on the driver side electric door lock and reinstalling the lock plunger in my 81 I noticed some strange voltage readings when the ignition key was in the off position. With the negative cable disconnected from the battery, I connected my multi-meter from the negative battery terminal to the metal frame of the door and get a reading of 12.5 volts. I tried doing the same by touching other metal parts of the car with one probe and the other on the negative battery terminal and got the same results.
Also, during the troubleshooting process I found a short between one of the RED hot wires from the starter and the ground cable in the starter harness in the engine compartment. It looked like the two got plugged in incorrectly, possibly when the engine was rebuilt. The only way I found this short was while the engine was running I moved the wires and the engine would stall. I repaired this issue for now to monitor and ordering a new harness.
The issue though is, why would I constantly get a 12V reading from my multi-meter when the car is turned off? I checked a few circuits by pulling fuses, courtesy lights and air/heat/blower motor but they wer not the culprit. still searching, I did notice the previous owner ran a red hot line from the battery to the power antenna, so I am going to check that circuit next.
Anyone have any ideas what could be causing the constant 12v reading?
Thanks
Also, during the troubleshooting process I found a short between one of the RED hot wires from the starter and the ground cable in the starter harness in the engine compartment. It looked like the two got plugged in incorrectly, possibly when the engine was rebuilt. The only way I found this short was while the engine was running I moved the wires and the engine would stall. I repaired this issue for now to monitor and ordering a new harness.
The issue though is, why would I constantly get a 12V reading from my multi-meter when the car is turned off? I checked a few circuits by pulling fuses, courtesy lights and air/heat/blower motor but they wer not the culprit. still searching, I did notice the previous owner ran a red hot line from the battery to the power antenna, so I am going to check that circuit next.
Anyone have any ideas what could be causing the constant 12v reading?
Thanks
Team Owner
Joined: Jul 2006
Posts: 22,162
Likes: 4,171
From: Kannapolis NC
You can't connect the negative meter lead to the negative battery terminal (with the cable disconnected) and a ground and use it for anything other than possibly current drain checks. The voltmeter completes the circuit that you disconnected and reading battery voltage is what you should get. That part of your issue is not an issue. You simply placed the meter into a series situation (in line) and it read as it should have.
Last edited by 65GGvert; Dec 19, 2015 at 06:58 AM.
Thread Starter
Pro
Joined: Nov 2014
Posts: 503
Likes: 66
From: Florida
You can't connect the negative meter lead to the negative battery terminal (with the cable disconnected) and a ground and use it for anything other than possibly current drain checks. The voltmeter completes the circuit that you disconnected and reading battery voltage is what you should get. That part of your issue is not an issue. You simply placed the meter into a series situation (in line) and it read as it should have.
Thank you for the education 65GGvert
