Posted to Technical Tips Forum on 3/8/2014
Maybe a tip like this has been posted before, if it has I
This week I had a car that was blowing 6 fuses. One of them
instantly and the others would blow randomly. I had
suspected a pinched harness somewhere. I decided to follow
the circuit that blew the fuse instantly.
That would be the 40 amp power window fuse. It was a
dedicated fuse for the 4 window motors and switches. The
harness leaves the under dash fuse box on the left side and
somehow goes to all 4 doors.
I installed my 30 amp fuse saver breaker into the receptacle
for the window fuse. Now this circuit goes all through the
car. In the past I would have cut wires if I could not
disconnect a connector to find the general zone of the
This time I put my amp probe around the harness in the rh
kick panel to see if the short was in the passenger side
doors. Resetting the breaker and keeping an eye on the meter
no current flow was observed. When I put the amp probe
around the power window wire in the left kick panel and
reset the breaker a brief 38 amp draw was observed before
the breaker popped.
Now I know the short is between the under dash fuse block
and the lf and or door. Putting the probe around both wires
in the door breakout harness showed no current flow. Ok the
short is in the harness between the fuse block and door
breakouts. Followed the harness and found it went under the
carpet on the drivers floor. Seeing as this would be the
area that would get the most use I pulled up the carpet on
the drivers floor.
Bingo there it is! The window wire had corroded which caused
it to create heat and melt the harness causing all the other
fuses to blow too.
So what I learned was instead of disconnecting harness to
zone out a short , if you use an amp probe to see if there
is current in that particular part of the harness you can
narrow down the location of the short.
Robert from New York
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54 Replies Received