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1979 Chevrolet Suburban K10 turn signal issues

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PorterS23

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Hello, I’m new to the forum. I recently purchased a 1979 suburban most of its issues I can figure out but this one is higher on the hierarchy and has me stumped at the moment. When I bought it and drove it home I had intermittent turn signals(sometimes the they would come on as the switch was moved and other times they wouldn’t) now all I have is the right turn signal showing solid(no flashing) in the cab when the switch is in neutral and on left and nothing when the switch is on right. Any starting points or information is appreciated.

 
First check the flasher switch is push in. Then check all your bulbs. They are an 1157, dual element bulb for brake and turn. This mean the brake and turn share the same bulb. Sometimes when a filament burns through it will touch the other filament. While you have the lens off inspect the ground wires to the body, should be nice and clean. No rust or corrosion. The bulb fit in socket, the lead contacts get deformed, corroded, and need to touch on the side, this the ground to the bulb.
After all that there will be 2 round metal or plastic can plugged into the fuse block. The top will be the hazard flasher and the bottom will be the turn signal flasher. Switch them. and test the results.

Also Welcome to CK5 @PorterS23
 
Wes Harden said:
First check the flasher switch is push in. Then check all your bulbs. They are an 1157, dual element bulb for brake and turn. This mean the brake and turn share the same bulb. Sometimes when a filament burns through it will touch the other filament. While you have the lens off inspect the ground wires to the body, should be nice and clean. No rust or corrosion. The bulb fit in socket, the lead contacts get deformed, corroded, and need to touch on the side, this the ground to the bulb.
After all that there will be 2 round metal or plastic can plugged into the fuse block. The top will be the hazard flasher and the bottom will be the turn signal flasher. Switch them. and test the results.

Also Welcome to CK5 @PorterS23
Click to expand...
Thank you, that helped a lot. I found that the flasher can for the turn signals was gone so I put the emergency flasher one in. I looked and found that at least 2 bulbs were burned out. And I found a ground wire had been cut so I fixed all that and now I have front indicators. But the rear ones both flash on both right and left. I have yet to check the grounds in the back so there might still be something I haven’t seen yet. Either way this is a MAJOR improvement over what I had before. I’ll update as I find things
 
Also in the rear check the trailer plug wiring, this is always suspect.

Glad you are making progress
:waytogo:
 
So, I’ve been working at it throughout the week and for a couple hours today. It’s where it was before with both front lights working as normal. I’ve come to find that I believe I have a short between the fuse block and the signal lamps themselves. In testing around I pulled the junction block and found that I had continuity between the turn signal wire and the brake signal wire(or at least what I could deduce to be either or) when at least to my understanding there should be none between those two wires as they should run parallel to each other. If somebody has a wiring schematic that would be great. I just ordered a Haynes book and should have it soon so maybe what I’m looking for will be in there.
 
My first suspect would be the turn signal switch. The switch can make or break continuity between tail and brake circuits.
So make the switch is in the neutral position, and double check your test. Then try the switch, in different positions.
There is a long slim connector, under column just below the dash filler panel. You should ohm check there too
 
Wes Harden said:

PDF of Square Schematics & GM Training Manuals - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PDF of Square Schematics & GM Training Manuals The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board
67-72chevytrucks.com

You can find down loadable schematics there.

Technical Service Manuals (view only)

(All Access) Downloadable GM Technical Manuals
ck5.com ck5.com

More factory info here
Click to expand...
Both of those links have all the same stuff. I just rounded it all up to upload here in case the other forum ever disappeared.
 
I replaced the switch when I bought the suburban because it was broken and I figured that that was the problem. Today I replaced the drivers side rear turn signal/brake light socket. I did notice in testing like you mentioned that when the brake lights were on I would go back to the original problem as demonstrated in my first video. I made a new one before the holiday and forgot to post it. It’s shows what I’m seeing right now. My Haynes manual came in so I’ve been looking it over. I’m about ready to just pull the trigger on a new wiring harness and just solve all the issues at once.

 
PorterS23 said:
I replaced the switch when I bought the suburban because it was broken and I figured that that was the problem. Today I replaced the drivers side rear turn signal/brake light socket. I did notice in testing like you mentioned that when the brake lights were on I would go back to the original problem as demonstrated in my first video. I made a new one before the holiday and forgot to post it. It’s shows what I’m seeing right now. My Haynes manual came in so I’ve been looking it over. I’m about ready to just pull the trigger on a new wiring harness and just solve all the issues at once.

Click to expand...
I’ll add that I took the tail lights off and disconnected the ground from the body and I still was getting power, albeit not much through the bulbs like it was bypassing and going through one of the power wires.
 
Has the trailer wiring been inspected? Is a rear only problem. I suspect a short between right and left turn. Green and yellow wires
 
I’ve looked at the trailer wiring. It all looks intact and correct. Granted I don’t have much of a point of reference for that but I can see what is in the manual. I did hit each pin with the volt meter and I saw a similar effect with 2 different pins showing the same voltage and cadence as the turn signals. I’ll get a better visual inspection on the green and yellow wires tomorrow and report back.

On a secondary note do you know if it is possible to swap an edelbrock 1406 performer onto the factory 2 barrel intake?
 
Have you checked to see if the Hazard switch is pushed in? With no flasher installed, it wouldn't flash, but would tie circuits together.
 
I’ve used the flasher during the diagnosis and have made sure that switch is off. Plus I would think that that would have both going but ‍idk
 
Not sure about an adapter for 1406 on a 2 barrel intake.
I think you're better off sourcing a 2barrel. I believe Holley still offers them
 
Thanks for the feedback. I dropped the 2 barrel carb I have off to be rebuilt today. In inspecting the wires today knowing what colors to look at I found that there was all sorts of crazy splices and that the wires that run the turn signals and brake lights had been cut in certain places and power spliced in from the trailer lights. I had looked under there before but was lost since I didn’t know what wire color was which. Now I have no power to the rear lights but at least I know why and can fix it. I have quite a few repairs in front of me but at least I can get it all tied back together now

Backstory on this: I have a 1994 GMC Pickup that needs and engine so I bought this suburban from the local junk yard as a donor vehicle. They had been using it as a plow vehicle before it developed a vapor locking issue a couple years ago. As the videos probably show, she is definitely rough but for what I paid I can’t complain especially since the issues I have had so far have been so simple. Even though my lack of experience with vehicles of this vintage definitely shows. I don’t know fully what I want to do with it yet. My life circumstances are kind of fluid at the moment so I’ve been trying to get it to where I can drive it down the road safely. Either so I can sell it to someone or so I can fix it up myself. I’ll be working on it slowly but by bit then I can take it up some trails as a hunting rig or whatever.
 
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