My 1989 Chevrolet Scottsdale 2500 has a short in the turn signal wiring system that we cannot locate. Every single light on the vehicle works however the turn signals do not flash. We replace the flasher. The four-way flashers work correctly and you can hear the flasher clicking. The fuse pops instantly once replaced and the ignition lock cylinders to the on position. We systematically disconnected all the lights in the system and it still instantly pops a fuse when the lock cylinders turn to the run position. We’re fairly good at identifying electrical issues and have done all the common sense test light testing and checked and verified all connections. It appears that the reverse back up lights and turn signals are one separate circuit and separate from the four-way flashers system circuit. Not having access to a hoist we have checked all the wiring that is reasonably accessible and do not see any reason for it to be popping fuses. Hoping someone here has come across this issue and can enlighten us as to what the fix might be. Thank you in advance for any insights that you may be able to reveal. Please read this entirely and don’t ask us to do the simple common sense stuff that we’ve already done. Looking for someone that may have Who may have had this unique problem and can give a specific direction.

 

1) If you have any trailer wiring, inspect for corroded connections and splices, even if it’s an in-line type harness. The wiring at the rear of the truck along the frame (from gas tank to tail lights) is susceptible to chafing and damage, particularly if trailer wiring has been installed.

2) The wiring on the steering column and the turn signal cam/switch are the next most likely suspects. Start with a good visual inspection of the wiring that runs from the bottom of the column to the switch. You don’t have to drop the column to do so but it does make inspection much easier - make your own call on that.

Here’s a wiring diagram if it helps you out. The connector at the base of the column isn’t shown and It’s been a while since I’ve seen one but it should be a separate connector from the ignition switch.

Diagnosis can go a few different ways depending on what you find and comfort level with a meter - I can clarify the next steps for isolating the circuits if needed.

 

Thank you for your insights. Earlier today I had the same idea of checking the trailer wiring harness leading to the six point socket. That’s next on the agenda. We had just popped the steering wheel off and replace the donut shaped turn signal assembly switch. Still popping fuses. We also had an extra gauge cluster so we unplugged the factory gauge cluster and trade the extra cluster still popping fuses. My nephew has a ‘89 Chevrolet 3500 almost identical to mine just a little heavier suspension and he had to change his gauge cluster to get rid of the gremlins in his lighting system.

 

It may also be helpful to remove the trailer plug from its housing to check for corrosion. It’s not uncommon for water and/or dirt to build up inside and cause short circuits.

 

And the fact I live in WISCONSIN were we use road salt. I agree with the thorough inspection.