Re: new to forum wiring issues

[revevans3]

I'm new to forum and appreciate the passion herein as i share it. I have an 81 short bed gmc 1500 with ls swap with th350 trans. I've put a 90 suburban core and front grill and lighting on the truck. I'm have and odd issue that I hope I can get some help with. I've read a lot of posts but can't seem to find one with my exact problem. If I missed one I'd gladly appreciate a link to it. Anyway, when I push the brakes all my front turn indicators come on. My bed is off the truck at the moment but I get power to rear turn signal wires on the connector when i press the brakes.  my turn signals don't work at all from the column switch lever (though I've replaced the flasher). interestingly my emergency flashers work properly.  all the front end lighting grounds look good and solid. I have not pulled the steering wheel to check the turn signal switch as I don't have a steering wheel puller but plan to borrow one tomorrow.

questions: would a bad turn signal switch in the steering column cause this? would the bed being off the truck and not grounded to the frame cause this? are there other grounds I might have missed that could cause this? any other suggestions would be greatly appreciated.

thx!

[bd]

By design, the front and rear signal circuits are normally isolated from one another through the turn signal switch.  An exception occurs when the 4-way flasher is switched ON.  In this instance, the front and rear signal circuits are connected together.  In other words, if the 4-way flashers are switched ON, depressing the brake will illuminate all of the signal lamps, front and rear, simultaneously.  Make sure the 4-way flashers are switched OFF when depressing the brake pedal. 

Otherwise, the turn signal switch could be shorted internally, or the ~18" long turn signal switch harness that runs down the steering column could be shorted, or the front and rear turn signal wiring may have been inadvertently misconnected during the LS swap.

Since the project is in-process, it would be prudent to verify all of the factory grounds, now.  Refer to the tech article Vehicle Ground for an inventory and description of the factory ground points.

[revevans3]

thx so much bd for the reply and help. I'll go and check all these grounds to make sure they're in place and get back. happy new year!

[revevans3]

well good news, the ground from the battery to the core support was bad so I repaired it and the lights are on. so that's great. thx! I have another question. I mentioned I've put a 90 suburban core and front grill and lighting on the truck.  which has side by side high beam and low beam on each side of the truck. when my low beams are on and I switch to high beams only my high beams come on and the low beams go off. I was thinking with the high beams swiched on the low beams should be on as well. Right or wrong? if i'm right, any suggestions? thx again

[bd]

89-91 Suburban, Blazer, Jimmy Quad Headlight Upgrade or Conversion Wiring

[revevans3]

wow thx for sending this link! really helpful. the drawing looks like it's going through a multi function (oem?) stem controller on the column. is it possible to adapt this wiring to the factory 81 HL control and floor dimmer? thx again

[revevans3]

one other thing. there's a diode in the circuit. what's the type and value of that? thx again

[bd]

Edit:  If you intend to build a new forward lamp harness and incorporate relays, it presents the perfect opportunity to upgrade to 12- or 10-gauge load wiring to feed the headlamps through a >20-amp circuit breaker.  It will make the lamps significantly brighter with decreased risk of overtaxing the circuit breaker should you decide to upgrade the lamps at a later time.

The attached schematic should work...