The Ford Barn

drolston · 12-12-2021, 08:20 PM

In trying to find my intermittent headlight short circuit (blown fuses), I came upon a mystery. With every switch in the car off, my Ohmmeter showed about 500 Ohms from the battery to ground. On my 12v car, that would result in a current leak of 24 milliamps, with the car turned off. That drainage would be pretty typical in a modern car with a lot of "keep alive" computer stuff, but for an old Ford, it should be completely open circuit, or zero drainage.

The only hot circuit that is not on a switch is the horn. Maybe the leakage is through that foam ring that insulates the horn ring from the column.

Any ideas?

12-12-2021, 08:20 PM	#1
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,811	Current Leak? In trying to find my intermittent headlight short circuit (blown fuses), I came upon a mystery. With every switch in the car off, my Ohmmeter showed about 500 Ohms from the battery to ground. On my 12v car, that would result in a current leak of 24 milliamps, with the car turned off. That drainage would be pretty typical in a modern car with a lot of "keep alive" computer stuff, but for an old Ford, it should be completely open circuit, or zero drainage. The only hot circuit that is not on a switch is the horn. Maybe the leakage is through that foam ring that insulates the horn ring from the column. Any ideas?