Sorry Guys and Gals, I just posted this in the wrong spot! Must be the weather? Lots of snow! Anyway I am working on a 1992 E-250 with a 5.8lt engine and with the key on I have a resistance value of just over 1 OHM in the ground wiring. With the key off I have no resistance? What is my best route to find what is giving me the resistance? Pull Fuses? Disconnect components? I am sure there are lots of options? I am hoping that someone may have come across this before.
Your help is appreciated,
Thanks,
David
From what 2 points are you measuring ground resistance??
Ground is not switched by the key, only +12V is switched, so I don't understand how turning the key on and of is changing ground resistance. You may be seeing a very small voltage drop with the key on that is effecting the OHMS reading on your meter.
You'll have to be a bit more specific as to where you are taking the measurment at. component and contact number. voltage can read thru components, such as a light bulb. to read one ohm, you must be using a digital multimeter.
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Tom Stangler
89 E-150 351W Tow rig for my Mustang
Virginia Beach, VA
I checked the resistance from the wiper motor ground to the battery ground, both key on and off. Digital multimeter was used, perhaps my choice of tool was not acceptable? Could someone please shed some more light on this subject.
Thanks,
David
I'm using a Haynes that covers up to 91. So there might be some difference. That said.......
If you unplug the wiper motor, and run resistance between the wiring harness plug, to ground, there should not be any difference with the key position.
if there is, that ground is missing/corroded.
According to my Haynes manual , the dash lights also use the same ground point.
Is something not working?
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Tom Stangler
89 E-150 351W Tow rig for my Mustang
Virginia Beach, VA
It started with a problem wiper motor that would not park so I started the diagnostic tree and found this ground problem. I have since repaired the motor, the pins were not completely touching for the park to engage when the washers were used. However this leaves me the question of the ground resistance? Normal or not? I would expect not, either with key on or off. As I have previously said the resistance is only there when the key is on. I do not see any other problems at this time and although the original problem and reason I posted is finished I am still interested in finding out the reasoning for the resistance in the ground wiring with the key on. Maybe by figuring this out I can divert a future problem and possibly save the computer or other electronic device that will certainly get affected by something like this.
Thanks for your interest,
David
I don't think you have a problem, and the increase in resistance you are seeing is not real. The extremely small voltage drop you are seeing (millivolts) is affecting your meter, trying to measure
resistance. To verify this, try switching your meter leads, and you
will see a negative (-) resistance reading with the key on!!!!
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