72 3.0 cs 25a fuse blows on ignition

adawil2002 said:
What was the last thing done to the car? Worked before what?

Had a similar issue a year ago, a screw nicked a wire and kept blowing the turn signal fuse, 2 hours to diagnose and fix.

You mention you are in Switzerland & car in London. Who is doing the trouble shooting?
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All the interior was pulled out and a stereo installed, but that doesn't run through the fuse box.

It's most likely a connector or punched wire.

I was in London over this weekend so I was looking at it. But its my dad who will be doing the troubleshooting he's and engineer so I'm sure he will find it.
 
Was power tapped from the purple power wire off the ignition for the radio? If not, that may be the culprit.
 
Hummerbeats said:
Yes the voltmeter is accurate to .00.
What we checked was voltmeter connected to fuse box and touched each end of the window wire switches and also the rear windscreen heater switch. All show a positive connection. I don't believe that should be the case.
Even when the voltmeter was connected between any of the window switch wires and the rear windscreen heater switch there was a positive connection, again I don't think that should be the case.

All these cables seem to be touching at some point. Just trying to find where that point is.

Will keep you posted with more findings need to trace if there is a break somewhere in the cables or loose connection.
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I presume when you say each window wire switch that you have isolated only the wiring that runs to fuse number 8. If not, we need to take a couple of steps back, but if this is the case, check for continuity to ground at each of the switch terminals.

Start with the rear windscreen switch. First of all, ensure the windscreen heater switch is in the off position. If it is not, this might indicate that there is a problem with the rear windscreen heater that is causing your trouble. If you find the switch was on when you did your other work, turn the switch off and try a new fuse. If the new fuse does not blow with the windscreen heater switch off, the problem is in your windscreen heater wiring. If the fuse blows again, check for continuity to ground at both terminals of the windscreen heater switch with the switch in the off position. If the switch is allowing continuity to ground on both terminals (meaning the switch has failed internally or the powered wire to the switch is grounded somewhere), this could be your entire problem. Identify which of the wires is powered, pull it from the switch and check for continuity to ground. If you have continuity on the power side, this wire is grounded somewhere, which also means the wire is probably physically damaged. You need to trace the path of the wire precisely and locate the damage. If you do not have continuity to ground on the power wire when disconnected, but you have continuity when connected to the switch, then your switch is the problem. If you can eliminate these potential trouble spots, then move on to your window switches.

Each switch should have a connection (and only one connection) that has continuity to ground. Do these checks and report back.
 
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