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post #1 of 3 (permalink) Old 09-28-2011, 05:13 PM Thread Starter
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Fuse keeps blowing

69 GTO 400 4bbl

I was driving a few days ago and my tachometer and cig lighter went out. Checked and the cig lighters fuse was blown. So I replace it with the correct fuse (sfe 20a), reconnect the battery, sparks fly, and it blows again. Same thing happens over and over, gone thru 3 new fuses. Car runs fine without it, tach and lighter just dont work. Any ideas? All wires and connections are solid. . . Possibly a short but where is the question.
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post #2 of 3 (permalink) Old 09-28-2011, 05:23 PM
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short is in the lighter housing at back. didn't think factory tach is on that circuit. if aftermarket one, then look at wiring to lighter.
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post #3 of 3 (permalink) Old 09-28-2011, 10:51 PM
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You have a dead short to ground. Here's how to find it. Using a test light, leave the fuse out, and connect the two leads of the test light to the fuse contacts. With the key on, the test light will light. Now unplug the power wire to the tach if you can find it. If the light goes out, then the short is on the tach side. If the light stays on, the the lighter side is the short. Unplug the power feed on the back of the lighter socket, light out means the socket is grounded inside, light still on means the power wire is shorted. Or if you have a multimeter set it to ohms(disconnect both battery cables, key off), with the com lead to chassis ground, touch each fuse contact with the other lead. One should read OL or no reading, other will show very low ohms, probably 5 or less. That is the shorted side, follow the same as above but look at reading on the meter, when it shows OL or no reading it is the same as the light going out. If the light stays on or the meter still shows ohms with both the tach and lighter unpluged, then check the power wire from the fuse box to where you unpluged the tach and to the lighter. Enjoy!

1969 GTO
1947 MGTC

"You can have it all, my emipre of dirt. I will let you down, I will make you hurt"

Last edited by 69Goatee; 09-28-2011 at 11:06 PM.
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