'94 suburban brake and hazard light issue.

[name]

Hi Guys,

1994 GMC Suburban k1500 , here is he deal :

All lights on the Suburban worked as they should but when I went to hook up the boat trailer I found that all running, turn, and emergency flashers worked on the tailer as they should BUT when I hit the brakes ALL of the lights on the trailer would go out ( but the brake lights on the Suburban still worked ) After a few days of moving the boat around the yard I now realize that I no longer have hazard or brake lights on the Suburban ( I still have running, backup and turn signals ) The trailer is now unhitched from the Suburban and I am trying to get the lights on the Suburban back to normal.

Here is what I have done :

1) The #9 fuse marked "brake" in the dash pannel was good but replaced anyway. ( no effect )

2) Researched the location for the brake light relay and have come across a couple of posts that say the Suburbans do not have a brake light relay . ( is this true for a 1994 ? )

A PO did install a trailer brake unit, I have checked the fuse for that and it is still good. I am not sure if this would have anything to do with the lights or not and I am not sure what to check next.


Many Thanks ,

 

[TreeGeared]

You need to look at the size of the fuse and the wire guage. If someone put to large of a fuse in the wire itself may have fried from too much current. In that case the fuse would be fine. Light circuits (Other than headlights) typically have no more than a 15 amp fuse. Otherwise get out a multimeter and find out where you do and do not have 12V. Either start at the light sockets and work back or at the brake light switch.

 

[Schurkey]

Perhaps a moderator will move this out of the Engine section, and perhaps into Towing; or maybe Audio + Electronics.

 

[name]

You need to look at the size of the fuse and the wire guage. If someone put to large of a fuse in the wire itself may have fried from too much current. In that case the fuse would be fine. Light circuits (Other than headlights) typically have no more than a 15 amp fuse. Otherwise get out a multimeter and find out where you do and do not have 12V. Either start at the light sockets and work back or at the brake light switch.

I did as you suggested, pulling the tail light housings and checking everything there, then moving to the wired in pig tail at the rear and cleaned up the ground wire for it. I got confused with the dark and light green wires finding one of them cut underneth a wire loom, so I decided to move back to the fuse pannel and double check the fuses again.

There I found a 10 amp fuse in a spot marked "stop" ( must of missed it the first time ) I pulled the fuse and sure enough it was blown. I replaced it with a 15 amp fuse ( what the panel says goes there ) and now everything on the truck side works as it should.

I will have to take apart the socket (7 pin ?) wiring and try to figure out what is going on back there. But for now I am confused what the #9 "brake" fuse is for ?, when I found it the first time I thought it was for the brake lights but apparently not ( the fuse marked " stop " controls the brake and hazard lights )

I am not all that great when it comes to electrical stuff so hopefully I can come across a wiring diagram with a factory tow package so I can wrap my head around it.


Many Thanks TreeGeared, I appreciate your help.