Irritating electrical problem

[Maddog53]

Fairly new to me: kinda rough 1970 K-10 197K miles, Older Goodwrench crate sbc w/HEI, sm465, np205, ps, no a/c, wiring and electricals appear in pretty good condition.

The snag: Ignition "ON" and selecting a turn signal: The instrument panel's turn signal indicator lights go wonky when the headlights are also on.

The actual outside turn signal lights themselves work just fine regardless if the headlights are on or off. Likewise, the headlights work fine whether the turn signals are on or off. ONLY the instrument panel's indicator lights (including the high beam indicator light) malfunction when the headlights are "ON," AND the turn signal switch is activated to either side (L or R).

The malfunction seen is a dimmed pulsing of one or both (if high beams are selected) instrument panel turn signal indicator lights, or blinking of the wrong side (L or R) inst panel turn signal indicator light, and usually accompanied by a pulsing of the high beam indicator (if hi's are selected) in rhythm with the selected turn signal blinking.

Also rotating the headlight switch knob to dim the panel lights makes the turn signal indicator lights blink on the wrong (L or R) side...

Again, this is an instrument panel indicator light problem only; all the actual outside lights work perfectly all the time. I replaced the high beam selector switch, but no change in the malfunction was seen. I'm thinking this is a grounding problem as opposed to a "short." Sooooo..... if this IS a bad ground, where would a fella go looking for the problem....

Or, would experienced owners like you look for something completely different? Headlight switch? PC board??? I'm hoping someone's seen this before, and can guide me in the right direction, before I totally disassemble the whole truck as I'm prone to do...

Thanks a million in advance for your help friends! -Lee

[MikeB]

Originally Posted by Maddog53

ONLY the instrument panel's indicator lights (including the high beam indicator light) malfunction when the headlights are "ON," AND the turn signal switch is activated to either side (L or R).

A couple weeks ago I saw very similar symptoms on a hot rod Ford with aftermarket instrument panel and a wiring harness built by the previous owner. It only happened when the parking lights or headlights were on.

Turns out the ground side of the turn signal and high beam indicator lamps were all tied together, but weren't grounded to the panel itself, the body, or the frame. I never did figure out how they lit at all, but grounding the bulbs to the dash fixed the problem.

So, check those grounds! On my 69, I think there is a single ground trace that runs around the printed circuit. Make sure that trace is grounded well. There should be very little resistance (0.5 ohms or less) between that point and the battery negative terminal.

[Maddog53]

Originally Posted by MikeB

So, check those grounds! On my 69, I think there is a single ground trace that runs around the printed circuit. Make sure that trace is grounded well. There should be very little resistance (0.5 ohms or less) between that point and the battery negative terminal.

Thanks, Mike! I think that's exactly my problem.... I'm thinking the gang plug that goes into the back of the instrument panel carries a ground.... Maybe that connection with the printed circuit floppy is bad ...or the surrounding trace has been compromised as you commented. Maybe adding some grounds to the panel, and to the pigtail to the panel's harness might help. I'll delve into it this weekend and report back....

Thanks again, -Lee

[72c20customcamper]

I had the exact same issue .My turn signals indicators were wonky on my 68 but only with the high beams on . Sometimes they just glowed other times if I turned the right blinker on the left indicator would blink and the right one would stay dark and it was reversed if I put the left blinker. Outside the lights worked normally . I tried grounding the dash instrument pod that did nothing . I then checked all the grounds on the truck . It ended up being the ground at the radiator support on the drivers side . Cleaned up the contact put some electrical grease on it a retightened the bolt with a new washer. Works perfectly now

[Maddog53]

Originally Posted by 72c20customcamper

It ended up being the ground at the firewall on the drivers side .

Thanks, Mark! That's gotta be my problem too! Where exactly was the firewall ground you cleaned up? Under the dash, or engine bay?

[72c20customcamper]

Originally Posted by Maddog53

Thanks, Mark! That's gotta be my problem too! Where exactly was the firewall ground you cleaned up? Under the dash, or engine bay?

Sorry not the firewall but on the radiator support . The one that comes of the headlamps it drove me crazy for a few weeks

I edited my post

[Maddog53]

Originally Posted by 72c20customcamper

Sorry not the firewall but on the radiator support . The one that comes of the headlamps it drove me crazy for a few weeks

I edited my post

Awesome! I bet that's my culprit too! Thanks, Mark!

[LockDoc]

-
Here is a pretty good thread on ground strap locations.

http://67-72chevytrucks.com/vboard/s...d.php?t=422234
.

[Maddog53]

Originally Posted by LockDoc

-
Here is a pretty good thread on ground strap locations.

http://67-72chevytrucks.com/vboard/s...d.php?t=422234
.

INTERESTING! I'll order the grounding strap kit and redo the whole truck....she's a bit crusty! Thank you very much!!!

[LockDoc]

Originally Posted by Maddog53

INTERESTING! I'll order the grounding strap kit and redo the whole truck....she's a bit crusty! Thank you very much!!!

Keep us posted on how it works out for you.

[Maddog53]

Originally Posted by LockDoc

Keep us posted on how it works out for you.

Will do! Just ordered a 5 strap set from Amazon for under 10 bucks.... will be here tomorrow!

Thanks, again! I appreciate all you guys helping me!!!

[Steeveedee]

It's quite pleasing how people rally around a problem a member has and helps them fix it! It's what makes this place so great.

[1970cstblazer]

My bet is grounding. There is a clipped on ground wire in the vicinity of the oil pressure gauge and ignition switch that is often dirty or knocked loose.

[Maddog53]

Originally Posted by steeveedee

it's quite pleasing how people rally around a problem a member has and helps them fix it! It's what makes this place so great.

100% !!!

[Maddog53]

Originally Posted by 1970cstblazer

My bet is grounding. There is a clipped on ground wire in the vicinity of the oil pressure gauge and ignition switch that is often dirty or knocked loose.

That's a really good possibility. I'll go search for that too, and secure it well!!!! Thanks!

[LockDoc]

Originally Posted by Maddog53

That's a really good possibility. I'll go search for that too, and secure it well!!!! Thanks!

I posted a picture of that ground in the linked thread I posted above. Check post #28.....

[MikeB]

Originally Posted by Maddog53

I'm thinking the gang plug that goes into the back of the instrument panel carries a ground.... Maybe that connection with the printed circuit floppy is bad ...or the surrounding trace has been compromised as you commented.

If adding ground straps doesn't solve the problem, Those printed circuits are reasonable priced.

As for the ground straps, I like to use external star washers on both sides of the bolt head to cut into the metal surfaces. Also, clean the bolt hole threads as best you can.

[Maddog53]

Originally Posted by LockDoc

I posted a picture of that ground in the linked thread I posted above. Check post #28.....

Yes, thank you!

Your post #28 shows both the clip-on ground and the plug-in instrument panel harness' ground, both of which could easily be the root of my truck's issue....

You guys are AWESOME!!!

[Maddog53]

Originally Posted by MikeB

As for the ground straps, I like to use external star washers on both sides of the bolt head to cut into the metal surfaces. Also, clean the bolt hole threads as best you can.

Brilliant! Thank you!!!

[71CHEVYSHORTBED402]

Originally Posted by MikeB

If adding ground straps doesn't solve the problem, Those printed circuits are reasonable priced.

As for the ground straps, I like to use external star washers on both sides of the bolt head to cut into the metal surfaces. Also, clean the bolt hole threads as best you can.

Pretty sure the factory installed them with star washers as described. But to my knowledge, only where the straps attach to the frame rail, hmm. Good idea, especially if there's a coating on the underbody that you're not prepared to remove. Perhaps not at the firewall and valve covers.

Seems they installed a star washer for the ground wire to fender, located on the negative cable terminal for side mounts, FWW.

And FWW, I used a pilot brush for every hole, short the valve covers and firewall. Really great finishes, and everything works. I suspect a frame can be so rusty the connections have to be cleaned.

[MikeB]

Originally Posted by 72c20customcamper

I ended up being the ground at the radiator support on the drivers side.

I don't thing my truck has a radiator support ground strap, but it sounds like a good idea.

[Maddog53]

Originally Posted by MikeB

I don't thing my truck has a radiator support ground strap, but it sounds like a good idea.

There is a grounding wire (not strap) that comes off the harness near the ext voltage regulator (driver side of rad support). It joins with a wire to ground the regulator and another wire to ground the headlights. This group of wires is bolted to the rad support just above (and inboard from) the voltage regulator...

A strap from the support to the frame couldn't hurt!

[72c20customcamper]

Originally Posted by MikeB

I don't thing my truck has a radiator support ground strap, but it sounds like a good idea.

It’s in the headlamp harness one on each side . The passenger side is behind the battery . If the ground is loose or has a bad contact it will backfeed looking for ground

[Maddog53]

Originally Posted by 72c20customcamper

It’s in the headlamp harness one on each side . The passenger side is behind the battery . If the ground is loose or has a bad contact it will backfeed looking for ground

Thanks.... I (incorrectly) thought the headlights shared a common ground wire.... I'll yank the battery tomorrow and make sure there's a good ground to the pass side headlight! Thanks, again!

[LockDoc]

Originally Posted by Maddog53

Yes, thank you!

Your post #28 shows both the clip-on ground and the plug-in instrument panel harness' ground, both of which could easily be the root of my truck's issue....

You guys are AWESOME!!!

That is the same ground. Goes into the harness from the clip
and comes back out at the cluster connector.