Ignition switch shorts when installed
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Postmaster
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From: O-O-O-Oreilly's
Ignition switch shorts when installed
Gents, I replaced the ignition switch on my truck and when I hooked it up and tested it, it worked perfectly. When I installed it in the dash, it barely cranked and made a lot of heat. Touching any conductive surface on the truck did this. The switch works great hanging free. Any ideas? Thanks in advance.
Fleet Mechanic
Joined: Nov 2009
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When you rewired the truck, did you splice into the terminal block for the ignition switch or run wires straight to the terminal lugs of the switch itself? Either way, use an ohm meter and see if any lug has continuity to the switch body. If so, check the wiring diagram to see which wire is shorted. It sounds like a shorted switch in all probability.
Fleet Mechanic
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Yes, switch can be shorted, unfortunately. Best bet is to disconnect battery, remove switch and ohm out the lines to switch body.
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Postmaster
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From: O-O-O-Oreilly's
Thanks, Filthy Beast, I will try that next. I am reading resistance through all wires that would go to the switch, through to the dash, column and clutch pedal. The only wires that do not read resistance are the battery wires. These are the ones that get hot when cranking.
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Postmaster
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From: Taxachusetts
You're welcome. You would have some resistance through the wires, albeit minimal. The best bet is to check the switch alone, without wires attached, as shown above.
Hopefully, no wires, fusible links, etc, got fried when the switch got hot. Bad things can happen, like electrical fires...unless you have some marshmallows.......
Are you running a neutral safety switch?
And, sheesh! A brandy new harness and all these problemos? Man!!!
Hopefully, no wires, fusible links, etc, got fried when the switch got hot. Bad things can happen, like electrical fires...unless you have some marshmallows.......
Are you running a neutral safety switch?
And, sheesh! A brandy new harness and all these problemos? Man!!!
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Postmaster
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From: O-O-O-Oreilly's
So I checked the switch. I have a different unit than the one you pictured, but I was able to find a test schematic for my switch. All is good, except I can't seem to get any continuity to go from the P terminal to Ground. It seems like there is, since the body of the switch is indeed zapping any conductive surface it touches.
The resistance through the column and wires was quite high as I remember. It is a manual, so no NSS.
The resistance through the column and wires was quite high as I remember. It is a manual, so no NSS.
Fleet Mechanic
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Next, I would install the switch, but leave the harness off. Do the ohm check on all leads again. If everything reads correctly, the switch is good and you will need to look at the ignition switch harness block next. It may be possible that something is bending enough (inside the harness as well as outside) to cause a short when the switch is mounted. Did you use a new ignition switch harness block when you connected the new wires? Not critical, just seeing the next step in troubleshooting.
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