Help!! I have an 86 Chevy truck that keeps blowing the turnsignal fuse as soon as the ignition switch is turned on. Everything else works, lights, flashers, brake lights, wipers, etc. I can't find any bare wires anywhere and went up to a 30 amp breaker and it still blew as soon as the switch was turned on. Would it be safe to assume that the switch itself is bad since the fuse blows as soon as the power is on even though the turn signals are off?

unplug the switch harness and try it. If the switch is bad then the fuse won't blow. There is a plastic sheath that protects the wires inside the column, if this has been removed the power wire may have the insulation worn off and shorting out.

I'd first unplug the turn signal flasher can. (Not the hazard flasher can). Guessing the problem is more under the dash 'cause the brakes and hazards work.

OK, I replaced the flasher can and it blinked twice and the fuse blew again. I unpluged the can and the fuse blew again. Is it possible the fuse block itself is bad? I looked for a way to disconnect the switch but could not figure out how to do it.

remove the plate from under the steering column. Then look for a 3" long flat connector. When you unplug it the turnsignals, horn and brake lights will no longer work.

Running a little blind because I don't have a schematic on that truck. More suspect something else is causing that fuse to blow. I think the back-up lights are also on that circuit. I'd leave the flasher can unplugged and unplug the back-up light connector. Assuming the truck is an automatic, look for a connector plugged into the Neutral Safety Switch with a pink and green wire. Unplug that.

The switch John is referring to is at the base of the steering column, on the top. It will also have large purple wires going into it.

John how is your vacation going?

Originally posted by 64elcamino:
The switch John is referring to is at the base of the steering column, on the top. It will also have large purple wires going into it.

John how is your vacation going? It's over Philip. Just took a long weekend so back at work. The desk is a mess.
Not trying to moose in on your ideas Philip. It's just easier to pull the flasher can than the turn signal connector. Once the flasher can is out of the circuit, there is no power to the turn signal switch unless you hit the brakes (or turn on the hazards). Wish I knew for certain what else may be on that fuse.

Many thanks to both of you. I have a manual trans and as near as I can tell, the B/U lights are the only other thing on the circut. I tried to find the wire for the switch on the trans but didn't see it, only the transfer case lights/wire. I'll pull the connector from the column and do that check. Again, thanks to you both.

I worked on Chevy trucks as a fleet mechanic for 13 years and this is one problem I have never run across. I will see if I still have some wire diagrams when I get home from work to see where your back up light switch is. If it is a 3 on the tree it will be on the lower column, but the 4 speed should be on the trans, probably up on the shift tower. Could be the wire there is shorted out or has fallen off and got burned up by the exhaust.

Originally posted by 64elcamino:
I worked on Chevy trucks as a fleet mechanic for 13 years and this is one problem I have never run across. I will see if I still have some wire diagrams when I get home from work to see where your back up light switch is. If it is a 3 on the tree it will be on the lower column, but the 4 speed should be on the trans, probably up on the shift tower. Could be the wire there is shorted out or has fallen off and got burned up by the exhaust. Seems to make the most sense Philip. The back-ups run off a switched 12 volt line and GM had tied the back-ups to the turn signal fuse. Guessing it might be a pink or a pink/black wire.

FIXED!!! Turned out to be a bare wire for my backup lights. Thanks again to you both.

Hello, just a note of Thanks!

Had this exact issue in my '70 Chevelle SS 502 after utilizing my Hotchkiss suspension one day, and returning home with no turn signals or radio. Just couldn't find it because since I had my radio hooked up to the same circuit, I went through all of the other issues including the steering column, until I tried another search and found this thread.
Went to the garage (after a trip to the Auto parts store for more fuses) and first thing I did was disconnect the wire to the backup switch. Problem solved until transmission time, which is coming up anyway. Just have to remember to replace the switch when the racing parts are installed!

Thank you to all involved, I have my car back for a while!!!

FIXED!!! Turned out to be a bare wire for my backup lights. Thanks again to you both.

If I had seen this earlier I would have posted for you.

Back-up wires come loose and rub on the bellcrank.
This will take out the turn, signals as well.

Keep in mind, this is an ignition only active ciruit.
Tail, brake lamps are powered pretty much directly from the battery.

'nother thing to keep in mind, if you have a tilt steering column.
Repeated use of the tilt, will eventually break a wire in the column.
If ever you run into an issue where all the lights work when the wheel is in the down position----but some do not when the wheel is moved to a highe position----Gonna need another turn switch.

got 28 yrs and 400,000 miles on my 79 with a manual and tilt.
I have had to fix these very problems more than once.

This and a couple of fusible links are all the electrical issues I have EVER had with this truck:D