When i put the left signal the front light flahes. When i put right signal the hazard lights go on. Ive replaced signal switch, light bulbs, relays, fuses, even bulb boards. What culd it be.

Rachel Gomez

Asked by Jan 27, 2015 at 04:00 PM about the 1988 GMC Sierra

Question type: Maintenance & Repair

3 Answers

Bob Beaman

Possibly a bad connection or ground at one of the bulb sockets. Also might be the turn signal switch.


You need a schematic for that rig in that year with that specific type light arrangement. I foud them at autozone website. You may have to print several and tape them together legibly, then tack it to the wall. You would be concerned with the plug and schematic for the turn sig sw., the hazard sw. and the flashers. only you , know what specifically has been done to it, now you have to trace and test to find it. Are the parts plugged in exactly right ? are the wires different on one plug for some reason? who knows. Napa sells some of those harnesses and light parts and way cheaper than GM. but they may not be perfect. patience and perseverence my friend.


The stuff you would have already done must have included inspection of every bulb and ground for crossed filament trouble in bulbs with multiple filaments. Also you found socket trouble, and went for the printed circuit boards, but if you are wired for towing anything, it can be that the wires and connections with those come into play. I had a truck in the shop years ago like that where the wires were changed around compared to the part we were installing. we had to search the map.

Your Answer

Add photo

Related Questions


Looking for a Used Sierra in your area?

CarGurus has 39 nationwide Sierra listings and the tools to find you a great deal.


Search GMC Sierra Questions

GMC Sierra Experts

#1 FordNut
Reputation 190
#2 dandyoun
Reputation 110
#3 Js08016
Reputation 80
View All

Related Models For Sale

Used GMC Sierra 1500"
1,024 Great Deals out of 56,926 listings starting at $2,300
Used Ford F-150"
3,267 Great Deals out of 216,697 listings starting at $1,500
Used Chevrolet Camaro"
798 Great Deals out of 38,822 listings starting at $2,650
Used GMC Sierra 2500"
223 listings starting at $2,895
Used Ford Mustang"
733 Great Deals out of 41,077 listings starting at $900

Used Cars For Sale