Irritating electrical problem
 

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...:crazy:

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

Re: Irritating electrical problem
 

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.

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

Keep us posted on how it works out for you.

Re: Irritating electrical problem
 

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!!!

Re: Irritating electrical problem
 

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.

Re: Irritating electrical problem
 

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.

Re: Irritating electrical problem
 

100% !!!

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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.

Re: Irritating electrical problem
 

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!!!

Re: Irritating electrical problem
 

Brilliant! Thank you!!!

Re: Irritating electrical problem
 

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.

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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!

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

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!

Re: Irritating electrical problem
 

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

Re: Irritating electrical problem
 

Oh! Thanks... I didn't realize that. I (blindly) found the clip and wire intact, and in place, but I could not see if it was in a rusty area (probably was to some extent). I'm gonna pull the panel this weekend and get a better look at the whole thing!

Re: Irritating electrical problem
 

Regarding ground wires from rad support to rest of world, my truck hasn't had an external voltage regulator for the past 30 years. However, I'm getting around 14 volts to the headlights, so bolts must be making a good ground. But I still think a ground strap to the frame is a good idea. Grounding is something that's almost never overkill!