Chevy pick up, turn signal fuse blowing (solved)

[green 788]

Just for the archives, in case anyone runs into this. Here is how I solved the problem of the turn signal/back-up light fuse blowing.

 

1994 K1500, 4.3 engine, 5 speed...

 

First symptom, turn signals would not work. Got advice from several places online, some said change turn signal selector. That would have been a really bad and relatively expensive idea.

 

Turn signal back-up light fuse blown. Replaced, then found that it blew before I could get out of the drive way. Note: I have to go into reverse to get the truck out of the driveway. (clue)...

 

I checked the schematic in the Haynes manual and found that the turn signals and back-up lights are on the same fuse.

 

I found that by disconnecting the back-up light switch on the side of the 5 speed transmission, I could get the fuse to hold, and turn signals worked fine. Note: the switch in the K1500 (4wd) is on the side of the transmission, driver's side, and it's easy to get to. It is not on top, as some diagrams seem to indicate. It's a 2 wire switch, one of the wires is bright green... I think the other is pink, but it may actually be a different color. The switch screws in with a 7/8" wrench. A deep well 7/8" socket would be best.

 

I left the truck like this until the Virginia state inspection was about due, and then decided I would work on the problem. The odd thing was that the green wire running from the back-up light switch to the rear of the truck was not grounded out. (you do have to unplug the tail lights to test that wire, or else the wire will show ground through the bulb elements)...

 

With the key on the run position, there was constant voltage at the other of the two wires (pink, I believe) at the back-up light switch. So this wasn't grounded out obviously... and the green wire that feeds 12 volts to the back up lights when the tranny is in reverse was, as mentioned not grounded. But when I hooked it up to the back-up light switch, and put the transmission in reverse... the fuse would blow!

 

Weird... but I realized that it could only be one thing: A bad switch. The back-up light switch had to be grounding out that line when it was engaged. Checking this with an ohm meter proved that indeed that was the case.

 

Most of the time, a bad back-up light switch will either stay stuck, and lights stay on all the time... or else it won't work at all, and lights stay off.

 

But this switch had the unique problem (to me, anyway) of grounding out the 12 volt feed when you put the truck in reverse.

 

A new switch (less than 20 dollars) fixed this problem.

 

Dan

[mlc34588]

Hey I am still having this problem and have replaced the backup switch two times in a year. (Three switches and all were shorted out) I am about to replace the tail light assembly, since they are in rough shape and suspect maybe the circuit board in the light assembly might be a problem. I have checked the wiring at the switch and replaced the pigtail. I have tried to follow the poor schematic in my chilton manual but there is not enough detail to chase the wire though the truck.

Does anyone have any suggestions? I am getting very frustrated with my truck right now.

Edited October 20, 2016 by mlc34588

[mlc34588]

Replacing the backup switch and both tail light assemblies (with new circuit boards) has so far corrected the problem of the backup switch shorting out. I also have brighter reverse lights and they are also working the way they should be, lighting when I shift to reverse, not waiting to illuminate only after I release the clutch and am actually moving backward,

[Kris Burford]

I'm having some problem with 1996 gmc suburban k1500 5.7l automatically  no turn signals I replaced turn signal switch replaced flasher fuse other fuse i have emergency lights no left turn signal and no right turn signal

[thx1138v2]

I found good wiring diagrams at the AutoZone web site but they are somewhat buried. You have to setup a login and tell them about your truck. Then go to the bottom of the page and click on 'Repair Guides", the "Vehicle Repair Guides", then "Chassis Electrical", and finally "Wiring Diagrams." That takes you to a menu of wiring diagrams for the truck you entered earlier. Then scroll down and choose the scheamtic you want to view/print.