The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 09-19-2017, 02:43 AM   #1
ace347
Registered User
 
ace347's Avatar
 
Join Date: Jun 2015
Location: chanute ks
Posts: 15
Lightbulb ground issues and general wiring help

Here's the combo: I bought a 71 c20, mostly complete minus the engine. Over the past two years I've installed a 07 6.0l truck motor with the original granny 4 speed and replaced some of wiring if not tried to fix the rest. I almost have it road worthy (perhaps not technically road legal).

More specifics on wiring situation: The headlight harness is all new, because of farmer john butchery, courtesy of LCM. I took the engine harness off. I pulled out the dash harness and went through it, deeming it worthy of re-installation since there wasn't any splices or rats nest. The chassis wires that go back to the rear is original except for a patch or two. The tail light harness is new as-well. The gauge cluster is in-tact and I got all the gauges to work ('cept speedo cause cable and all). I am missing the wiper switch(plan to take care of that tho). all the bulbs, fuses and blinker switches are new and they all seem to work in some way shape or form. (no bulbs in rear markers yet). No fuel tank wiring(removed in-cab tank). No interior lights aside from dash lights.

The symptoms: When I turn on the running lights the passenger front side marker does not light up. With the lights on, the passenger tail lights works great but the driver tail light is dim and when you step on brake it turns off completely. When the lights are off the tail lights work as they are supposed to but the driver stop light is very dim. The blinkers do not work by them selves but the hazards work just fine, even the pass front marker blinks. The gauge lights don't work when the lights are on. The e-brake light comes on when cranking the motor but not when the e-brake is actually utilized. The turn indicators on the dash come on with-out blinking only when hazards are engaged. I have one mystery plug under the dash that I assume is to the missing wiper switch(three prong in the shape of a mostly flattened L). The back-up lights don't work yet 'cause the reverse switch pigtail goes through the engine harness.

I understand that there is a ground issue somewhere but I'm not sure were to start looking. I'm a novice at best when it comes to diagnosing these problems and a multi-meter is Greek to me. I found diagrams but can't figure out what I may have missed.

My question is if the main fuse box ground is on the engine harness that I excluded. I would appreciate any tips or tricks you can give me.
ace347 is offline   Reply With Quote
Old 09-19-2017, 08:09 AM   #2
notsolo
Registered User
 
notsolo's Avatar
 
Join Date: Apr 2008
Location: Md
Posts: 2,481
Re: ground issues and general wiring help

You have probably done this, start under cab, clean frame and ground strap area on cab new star washers might help, move on to front end and frame, motor to battery etc. Good luck.....Welcome aboard also.
notsolo is offline   Reply With Quote
Old 09-19-2017, 09:05 PM   #3
68c10airstream
Registered User
 
68c10airstream's Avatar
 
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
Re: ground issues and general wiring help

Take a look at the right hand inner fender on the underside up front. I think a braided strap goes from inner fender to frame rail on passenger side. Obviously the engine is grounded because the starter works ok, the cab is on rubber mounts and that it grounded from braided straps from the heads or valve cover bolts to the firewall. I've changed my battery location but i think a ground went from the battery cable at the battery to the rh side fender. So look all over the frame for a braided strap, but i think my 68 c10 is as mentioned. Good luck!
68c10airstream is offline   Reply With Quote
Old 09-20-2017, 10:40 AM   #4
engineer_gregh
Registered User
 
engineer_gregh's Avatar
 
Join Date: Feb 2012
Location: Smyrna TN
Posts: 1,153
Re: ground issues and general wiring help

I had to ground my bed to the frame to make my marker and tail lights work correctly. One other thing is to make sure the tag light wire is not broken and grounded to the frame.
__________________
1971 Longbed BB Cheyenne Super
1972 Longbed SB Cheyenne Super
1972 Longbed Highlander Custom Deluxe
1975 K5 4x4 full convertible

Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=645165

Greg Smyrna TN
engineer_gregh is offline   Reply With Quote
Old 09-20-2017, 12:08 PM   #5
VetteVet
Msgt USAF Ret

 
VetteVet's Avatar
 
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,717
Re: ground issues and general wiring help

You have too many problems to just start groping through the wiring harness blindly. You will have to learn the circuits and what the different colored wires do.
Above all you need to get yourself an multimeter and learn how to use it.
Here is a very good tutorial from U tube.

https://www.youtube.com/watch?v=zb7WHaL_dz8

They vary in design but most of them are similar. You can get one from Walmart, harbor freight sears or just about any auto store and $20 will buy all you need.

When you get familiar with using it we will start diagnosing your problems.
__________________
VetteVet

metallic green 67 stepside
74 corvette convertible
1965 Harley sportster
1995 Harley wide glide

Growing old is hell, but it beats the alternative.
VetteVet is offline   Reply With Quote
Old 09-20-2017, 07:00 PM   #6
68c10airstream
Registered User
 
68c10airstream's Avatar
 
Join Date: Mar 2013
Location: Marquette michigan
Posts: 828
Re: ground issues and general wiring help

ace347, Vettevet has stepped up to the plate and you are in good hands. His commitment to help and wiring knowledge with pics is the best. Learn and enjoy, good luck
68c10airstream is offline   Reply With Quote
Old 11-15-2020, 05:02 PM   #7
badlands122
Registered User
 
Join Date: Mar 2015
Location: Deer Park, Tx.
Posts: 3
Re: ground issues and general wiring help

Quote:
Originally Posted by notsolo View Post
you have probably done this, start under cab, clean frame and ground strap area on cab new star washers might help, move on to front end and frame, motor to battery etc. Good luck.....welcome aboard also.
damn nice work!!!
badlands122 is offline   Reply With Quote
Old 11-15-2020, 07:55 PM   #8
Andy4639
Old member
 
Andy4639's Avatar
 
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,945
Thumbs up Re: ground issues and general wiring help

VetteVet, is the man when it comes to electrical.

Just some general things to look at first.
Battery of truck grounded to frame are motor.
Motor grounded to frame.
Cab grounded to motor
Cab grounded to frame both sides
frame to bed both sides.

All light housing's are grounded to the metal of the truck some how. Clean all spots good.
Dash cluster should have a ground wire running to the dash also seperate from the harness.
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver
Seeing the USA in a 71


Upstate SC GM Truck Club
2013,14 and 2016 Hot Rod Pour Tour


http://upstategmtrucks.com/



Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
Andy4639 is offline   Reply With Quote
Old 11-15-2020, 10:53 PM   #9
LockDoc
The Older Generation


 
LockDoc's Avatar
 
Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,647
Re: ground issues and general wiring help

-
Old thread and the OP hasn't been on since 5/16/20. Don't know why it never went any farther. It ended kind of abruptly.....

LockDoc
__________________
Leon

Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles

(My Dually Pickup Project Thread)

http://67-72chevytrucks.com/vboard/s...d.php?t=829820

-
LockDoc is offline   Reply With Quote
Old 11-21-2020, 03:02 AM   #10
ace347
Registered User
 
ace347's Avatar
 
Join Date: Jun 2015
Location: chanute ks
Posts: 15
Re: ground issues and general wiring help

Sorry for not coming back, but I did figure it out, the hard way.

Apparently I wired all my turn signals wrong. The wireing instructions were not very clear from LMS. They claimed that if you had this one year, you use this wire and not that wire and so forth.

I eventually just made some jumper wires for the weather packs then trial and errored it till they worked. I can't remember the specific wire colors that I ended up with at the moment though.
ace347 is offline   Reply With Quote
Old 11-21-2020, 03:40 AM   #11
vics stuff
Registered User
 
Join Date: May 2011
Location: Reno Nevada
Posts: 384
Re: ground issues and general wiring help

I learned this from a old low voltage electrician. Everywhere you have a ground , always use a external star washer between the wire and the item that you are grounding to. that will end your grounding issues.
Vic
vics stuff is offline   Reply With Quote
Old 11-21-2020, 08:35 AM   #12
BigBird05
Registered User
 
Join Date: Aug 2019
Location: Cheraw
Posts: 1,300
Re: ground issues and general wiring help

The frames on the 67 thru 72 trucks are riveted together. Not welded like newer ones. Over time (50+ years) those riveted joints rust (Resistance). This method worked fine when the truck was new. Running ground wires down to the frame will not always fix the problem. To use the frame as a ground you would need to run a ground wire from the left hand frame rail over to the right hand frame rail. Then you need ground wires from the radiator support to the frame, fenders to frame, cab to frame, box to frame and in your case, remote gas tank to the frame.
BigBird05 is offline   Reply With Quote
Old 12-05-2020, 10:54 PM   #13
ace347
Registered User
 
ace347's Avatar
 
Join Date: Jun 2015
Location: chanute ks
Posts: 15
Re: ground issues and general wiring help

But it wasn't a ground issue though. That was the first thing I checked for and every thing was good.

The problem was that the turn signals seemed to have a mind of their own. Like THEY decided when to blink and when not to. It was frustrating because it took me a while to nail it down because I would swap a wire here or there and it wouldn't fix any thing. I went through turn signal switches, replace the dash harness, swapped the lights back and forth, even ran a ground wire straight to the battery.

The problem with LEDs is you can wire them backwards and they will still work. ask me how I know. That was were it all went wrong. Because they were wired up backwards they would blink when they weren't supposed to. Not blink at all when they were, and simply shut off when the headlights were on.

But I fixed it and my truck looks like a xmas tree at night now and I love it all the more for it.

THE FIX: for LMC led light on a 71 Chevy truck
LMC light | D F | D R | P F | P R
Red wire > black | red | blue | red
Black wire > brown | brown | brown | brown
White wire > ground
ace347 is offline   Reply With Quote
Old 12-05-2020, 11:18 PM   #14
LockDoc
The Older Generation


 
LockDoc's Avatar
 
Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,647
Re: ground issues and general wiring help

Quote:
Originally Posted by ace347 View Post
But it wasn't a ground issue though. That was the first thing I checked for and every thing was good.

The problem was that the turn signals seemed to have a mind of their own. Like THEY decided when to blink and when not to. It was frustrating because it took me a while to nail it down because I would swap a wire here or there and it wouldn't fix any thing. I went through turn signal switches, replace the dash harness, swapped the lights back and forth, even ran a ground wire straight to the battery.

The problem with LEDs is you can wire them backwards and they will still work. ask me how I know. That was were it all went wrong. Because they were wired up backwards they would blink when they weren't supposed to. Not blink at all when they were, and simply shut off when the headlights were on.

But I fixed it and my truck looks like a xmas tree at night now and I love it all the more for it.

THE FIX: for LMC led light on a 71 Chevy truck
LMC light | D F | D R | P F | P R
Red wire > black | red | blue | red
Black wire > brown | brown | brown | brown
White wire > ground

I have read on here that the LED's are polarity sensitive. Glad you finally got it sorted out.

LockDoc
__________________
Leon

Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles

(My Dually Pickup Project Thread)

http://67-72chevytrucks.com/vboard/s...d.php?t=829820

-
LockDoc is offline   Reply With Quote
Reply

Bookmarks

Tags
c20, truck, wire


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:22 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com