Author Topic: turn signal fuse blowing  (Read 137 times)

Offline frankenstein

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turn signal fuse blowing
« on: March 14, 2019, 11:33:38 AM »
1987 chevy pickup 4x4
Automatic 700r4
I have been chasing an electrical problem for some time now with the turn signals. I checked the wiring mainly at the rear lights and under the bed and found a few abrasions so i fixed them. Checked all connections in the rear taillights and re-grounded what originally existed. After doing this, I replaced the turn signal fuse and started the truck. All is well. I turn the blinkers on and turned the wheel back and forth, shifted into drive and reverse bc originally it seemed like when i shifted into a gear or turned the wheel it would blow the fuse. Not this time so i take it around the block and notice my turn signals arent working again. Checked the bulbs in the taillights just to make sure and they were all good bc after replacing the fuse again, everything worked as it should. Well im back to chasing this short. I thought for sure, turn signal switch. So i ripped apart my the steering column unwillingly and replaced the switch and lock cylinder while i was in there. After a nightmare trying to get the rack and selector in the right position so the lock cylinder lines up and the key operators everything as it should, i again replace the turn signal fuse and start up the truck. The blinkers finally work! I throw it in drive and go about 30 ft. So far so good. Throw it in reverse and back up. Turn signals dont work again  >:( What the heck? Anybody have experience or ideas? Id appreciate anything at this point. thanks

Offline MIKE S

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Re: turn signal fuse blowing
« Reply #1 on: March 14, 2019, 01:15:13 PM »
Have you checked the wiring going to the front bulbs. Trace out of bulkhead to radiator support. I would open up the conduit to make sure that all wires are not just shortening to ground but shorting to other wires in loom. Very sharp corners around radiator support. Also check front corner lamps for abrasions. Also the indicators in the cluster. Check the instrument cluster harness for shorts the dash metal frame parts.

Offline hatzie

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Re: turn signal fuse blowing
« Reply #2 on: March 17, 2019, 09:55:42 AM »
As odd as this sounds.  Pull out the bulbs and check that there's not some kind of conductive smut in the socket or on the bulb base.  The anti-corrosion goo shouldn't do this but I've found metal pieces in bulb sockets with no good reason it should be there...
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Offline bd

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Re: turn signal fuse blowing
« Reply #3 on: March 17, 2019, 11:50:32 AM »
Another place to look is above the driver side rear axle where the exhaust pipe passes close to the rear lamp harness anchored between the flanges of the left frame rail.  Exhaust heat can compromise the PVC wire insulation resulting in cross-feeding, short circuits and grounds.  Melting of the harness becomes acute if the plastic anchors retaining the harness to the inside of the frame rail are broken, allowing the harness to sag out of position.  In cases where steel harness clamps were used in lieu of plastic, wire insulation melted by exhaust heat can allow rear lamp wires to ground to the frame as they pass through the clamps.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Wickman

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Re: turn signal fuse blowing
« Reply #4 on: March 18, 2019, 06:02:19 AM »
I have an -83 so Im not sure we have the same wiring, but i guess its the same. Reading your story it seems to be a connection to the back-up light and for sure it is. They share fuse 15 amps, signal flasher and buck up light. If you disconnect the blue cable from the fuse panel to the BU switch on your column, will that change the behavior?