Hmm. Inside turn signal indicators function differently with headlights on
 

Added a tach so had to remove the instrument cluster and replace the printed circuit. Other than that, no changes, just remove and reinstall, have done this many times on several trucks.
So... now that it's all back together, turn signals work great with the lights off (all outside turn signals and all inside turn signal indicators). With the headlights on, however, selecting left turn signal results in a right blinker indication on the dash (but all the external turn signals blink as the should based on the position of the turn signal lever). Opposite happens when right turn signal selected (inside blinks on the left, and outside are all indicating as they should be). So, it's safe to drive, since what I select on the turn signal indicator is what actually happens on the outside, regardless of headlights on or off. It's only when headlight are on that the inside (only) indicators indicate backwards. Can't just be something simply like wires in the wrong place - it's a printed circuit board, only one way to go on.

I "thought" it might be the fact that the printed circuit was kinda scrunched because of a ground connection on the circuit board that wasn't quite where it needed to be, so removed it and smoothed the cb out, made no difference though. And one time, it just started working... shut the truck down, and then when started up again, it was back to the inside turn signal indicators blinking the opposite side when the headlight switch was on.

Anyone ever seen this before? Getting kinda tired of taking this silly thing in and out, thought I'd see if anyone has any ideas.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

the plot thickens.. When brights are "on" with headlights on, both turn signal indicators come on (and selecting left or right turn signal with the lever still gets the normal, correct response on the outside turn signals). Weird behavior. All these connection on the main harness are on the upper side of the harness plug - all wear marks on the the printed circuit look perfectly centered where they should be in the copper connections, no 'tweeners'. Hmm.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Lights that operate "weirdly" usually indicate a loose or bad ground. Voltage looking for a ground path can cause some "silly things" to happen. When you re-installed the cluster, did you also reconnect the ground wire? it's the one with the clip on the end. it attaches to a suitable location on the steel dash.

Also the screws that attach the CB to the cluster panel are part of the ground path, they need to be clean and tight.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

thanks Rusty, I'll take a look, agree it does act like a bad ground - but I don't recall seeing one when I removed the whole pile of parts - where is the ground wire you're referring to on the cluster? I thought the grounds you mention that are part of the printed circuit retainer were the only ground path - that and the ground built into the harness connection. If there's a separate ground wire, I may have missed that, where does it connect/tie into the cluster? And thank you for the reply.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

There is a ground wire in the cluster plug harness. It's the only black wire in the cluster plug. In some of the vehicles this wire is dangling free from the wrapping. In most, it's in with all those other wires, but it exits after a short distance, still very close to the back side of the instrument panel.. It normally clips to the lower right corner of the panel opening. The metal housing on the cluster panel is not the ground, it's only part of the ground path. The screws pass through the ground trace on the PC board. From the factory, the ground wire doesn't have a ring terminal for a screw. Look for it, Jocko.. It's out in the open, not concealed behind something. It will be on the back of the dash in the general area between the steering column and ignition switch.

If you can't find it, locate the only black wire on the plug (it's one of the wires on a corner of the plug), and splice a piece of 18 ga. wire (preferably black) to it and ground it to a suitable spot.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Thanks Rusty! I am familiar with the black ground wire of the harness in the 7 or 12 position, I forget which, on the harness connector - but good point to trace where it comes out and attaches to a good ground on the other end. That would be something I wouldn’t have disturbed in the removal since I only unplugged the harness, but who knows it may have gotten knocked around in the process - I replaced my heat and a/c ducts as well and I’m lucky there’s anything left intact underneath the dash after that ordeal. I’m also starting to suspect I criss-crossed the column light with one of the illumination backlights on the printed circuit. In the dark I noticed only the fuel gauge was backlit. I’m battin a thousand… ha. Thanks for the note, I’ll definitely check out the ground.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Definitely a ground problem. I had the exact same symptoms that you describe. I pulled my dash panel and cleaned all the grounds. Problem solved.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Well, not so sure it's a ground problem after all. Rusty, the black ground wire connection to the lower right of the dash opening is still there and intact. Since it was hard to tell in the maze of a/c ducting where it actually re-entered the harness, I tested the ground circuit for continuity and it was good to go; I also hooked up a separate ground wire to the back of the tins with one of the existing screws and to a clean solid ground location with a donor piece of wire and some ring terminals just for troubleshooting purposes. Same exact problem persists.

With parking and headlights off: everything works perfectly (except the fuel gauge -which is another bit of a mystery since the new sender tested good before install (and before instrument cluster swap, it read close to zero (but I also only had a couple gallons in the tank, so assumed it was good) - but post instrument cluster swap, it's pegged to past full (which normally indicates a ground problem - this happens with headlights lights on or off)).

With parking or headlights on: the only instrument lighting that is lit up is the fuel gauge, rest dark; the turn signals glow when no turn signal is selected, and the when the turn signal IS selected, the opposite instrument cluster turn indicator blinks (but all external indications are as expected); and things behave slightly differently when the brights are also on. All the wiring appears to be intact, no work peformed on the harness itself, just tucked out of the way when the cluster was out, Two solid grounds for the cluster, both original and a secondary test ground between cluster tin and solid ground location under-dash..

Elec gremlins drive me nuts. I'm no electrician, but also not exactly a novice with the electrical side of the house either. So gonna need to do a little more troubleshooting. I would think that if there were a bad original ground, the secondary ground would at least eliminate that issue for testing purposes.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Jocko, Those symptoms all indicate a ground loss, or at least a loss to some of the items.. It's not unusual for a trace on the PC board to break.. In some cases, the break is almost invisible.. The ground trace "travels" all over the PC board.. Remove the cluster (once again!!!) and check the ground trace very, very closely..

Also make certain the pinout on the harness plug is correct for the gauge cluster. They are different, you know...

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Thanks Rusty, Agree everything indicates a ground issue, but there's no smoking gun yet, I removed and cleaned the factory instrument cluster at the dash (and the factory had it clamped over the interior paint, wasn't touching bare metal at all) - so I sanded it to bare metal on both sides with some 220 grit.

Cluster is back out now and I'm getting ready to do the printed circuit testing on the ground loop - finding a crack would be welcome news... (I did put it back in temporarily to see if the the cleaner ground helped, but it didn't - and I assumed it wouldn't because it also didn't help to have a separate test ground connected to the cluster and a good under-dash ground).

What IS odd is this - with the cluster out, I confirmed I've got 12V at the #8 cluster light pin when the headlight switch is on (and 0 when off). But when I connect the remaining standalone instrument cluster light (the one you'd remove when installing the instrument cluster because it is tied into the harness (for the trans shift indicator) to the #8 pin out and a good ground - it won't light up - this seems odd to me since whole printed circuit is eliminated in this scenario (and it's confirmed as a good bulb, lights right up when a 12V power probe and ground are hooked to it).

I'm not done troubleshooting, but work is gonna get busy again and this thing is likely to have to sit a bit. Anyone know a good mobile electrical technician in the DFW area? :) Wish I had time to tinker, I'm gonna have to retire if I ever want to have time to do work on the truck more than an hour or two every couple weekends, ha!

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Check your PMs.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Jocko One of the screws that hold the printed circuit to the cluster takes the ground from the cluster to the ground circuit in the printed circuit sheet. It will do exactly what you describe. Look at the common (ground) in the printed circuit going to the affected lights. There is one trace going to those lights with one screw going through it into the metal base. That is your ground for those lights. it must be clean and tight to work properly. Be careful not to twist the printed circuit. You can also use a star washer between the screw and printed circuit.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Thanks Rick, I know which screw you're referring to, it's upper left-ish when looking from behind if I recall correctly. I've got the cluster back out, that ground screw was tight - I still need to check the continuity of the ground circuit on the printed circuit when I get a chance. I hope I find something when I do, that would be a relief. Thanks for the reply, much appreciated.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Yep, Rick is correct, I second his motion.. I alluded to the importance of those screws in post #3..

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Jocko tight might not be enough. make sure the circuit is clean on top and bottom as well as the sheet metal base. Also a new screw can't hurt. Sounds like your on the right track.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

My 68 was doing the exact same thing . My problem ended up being the grounds at the radiator support.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Yeah them grounds ain’t no joke when missed.
I just payed my front bumper on box’s up front to check wiring. It did all kinds of crazy stuff to the lights on or off. Both lights on dash coming on green with nothing on.
But a jumper from bumper to the truck. Fixed it all to normal,
The only issue I have now is flashers won’t work unless I flip a blinker on. Right or left. Doesn’t matter which.
Any ideas on that ?

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Just following up since it's been awhile. Finally got a few days off of work and a chance to do a little troubleshooting. Did not appear to be a ground or printed circuit issue after all. Had some oddball continuity indications across the the high beam indicator lamp (things like no continuity across the bulb holder even though the bulb tested good, eventually, it was a little odd). Anyway, removed and reseated the bulb holder (with a new bulb anyway) and life is "bright" again :). Turn signals working fine on bright or dim as is the brights indicator - even the fuel gauge is working again (I think, won't know for sure til I get some more gas, but it's showing close to empty rather than pegged off the right). Seems an odd thing to cause so many issues, but at the end of the day, that's the only thing that changed. Cleaning all the grounds and even installing additional grounds for testing purposes didn't help the problem. Just wanted to follow up in case anyone else had a similar issue. Thanks again for all that pitched in to help, really appreciate it.

EDIT: And as soon as I began adding gas from a gas can I saw the gauge peg back to far right. These gas gauges sure are finicky... Electrical connection at tank is solid and had good continuity from it to the instrument cluster plug, and showed almost empty, as expected, until I added about 3 drops of gas, then pegged right again - so doesn't seem like a bad sender, which also tested good before install. Well, the sender ain't coming back out, I'll just keep track of my miles til I get a chance to troubleshoot it later (exactly like i did with my first 72 in the 80's.. some things never change). I need to retire just so I can have time to troubleshoot all the gremlins in this truck :)

Well, spoke too fast, now that the turn signals are working, none of the instrument cluster lights are. Fuse is good, gotta check the rest out when I get another chance to work on it, getting late here. It waited until I tightened the last screw of the re-install to go bad :) (truth in advertising, I did check the dash lights on the bench, all were good, but couldn't really check them on the truck as I was working in full sunlight, so more fun to go still).

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Did it all work good before the Tach installation? If so, I would be looking at the tach connections and lights. You could take the tach out and see if all is corrected.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Interested to see out come.
I had a nightmare problem.
Finally solved it.
Special thanks to member DonD bought a rebuilt column from him, and turned out it wasn’t the problem .but willing to replace
Member with good integrity. Appreciate that:chevy:

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

Interested to see the outcome of this also. Problems like this can drive a person nuts.

Re: Hmm. Inside turn signal indicators function differently with headlights on
 

I believe everything was working before the tach was installed. However, the tach operates independent of the new printed circuit, it connects directly to the fuse panel and the coil (and works fine except, like the rest of instrument panel, doesn't light up when the headlight switch is on - which kinda makes sense, if the rest of the instrument panel isn't backlit, the tach would not be either (I think) - because I "think" the inner two (of four) instrument panel backlights are the ones that also light the tach if equipped). But good question and good point, I have considered popping the old instrument panel parts back in w/o tach just out of curiosity - I'm starting to wonder if my instrument panel lights ever worked, I haven't driven it at night in ages. But I know they lit up on the bench when I checked them with a power probe, all of them individually and also by powering the harness connector gray wire. So, something's just not adding up. Could be bad headlight switch, but I usually tend to suspect the things I've changed more than the things I haven't when something goes south... ha.

yep, it's sure drivin me :crazy: