67 deville more cluster hiccups

[TomB]

Devil is in the details. Finally the instrument cluster in, but half of the meters, bulbs, lights don't work. Usually ground is the culprit, according to the shop manual several ground wires have to be hooked up...but from the printed circuit, lightswitch, wiper switch, climate control, radio or else?

[Cadman-iac]

  Hi Tom,
I am not familiar with the 67 dash, but I did want to ask, did you figure out which way the connector plugs into the cluster?
If I'm not mistaken, I believe that one of the connections on your printed circuit board is a ground. Do you have a service manual that you can check for a schematic to verify that?
Also,  the connection between the terminal block and the printed circuit board is somewhat delicate. It's not really a circuit board,  but a flimsy piece of plastic with the circuits laid on top in copper strip. The point where it contacts the connector block, or terminal block, whichever term you prefer, is pushing up against the terminals in the connector block, and they don't actually have a positive inter-lock between them like most  of the other connections in your harness, so it's possible that you don't have a good connection on some of those. The opening where the connector block goes and the circuit board wraps into it is where the connection is made. The circuit board is "pinched" between the connector terminals and the cluster housing inside that opening.
I have taken a little pick or small screwdriver and pulled outwards slightly on the terminals in the connector block to make them protrude a little more, as they sometimes will settle over time, and might not put as much pressure on the circuit board as it used to.
Also, the little ends on the circuit board that are supposed to contact the terminals could have accidentally been deformed during the handing of the cluster and now they won't make contact. Have you looked at that to make sure they are all uniform and none are pushed back too far?
I don't know if there's a separate ground wire that goes between the cluster and the body metal someplace, but that's where your schematic will come in handy.
Beyond that, I don't know what else you should look at. Did the stuff that's not working now, work before you removed the cluster? If so, the connection may be the reason. If not, check the circuit board for any burnt places, or broken strips somewhere. A power feed strip might be damaged and not powering some of the lights or gages.

Good luck,  I hope you find the problem.

Rick

[TomB]

Hi Rick, thanks for the feedback. Will certainly try some of your options tomorrow. The terminal/connector that goes into the mylar circuit board has a shoulder on one side, but the board has no opening and the layer beneath it neither. Will scrape of the shoulder (see picture) since it serves no purpose, it might actually disable proper connections. It is quite obvious that the side with the numbers 1 to 6 should face up. I found the car in pieces, so have no recollection how to put it together again. The shop manual is quite vague on where to put ground wires and schemes don't show routing of grounds either. I believe that the climate cluster, lights, wiper have nothing to do with the flexible mylar board and probably might need their own ground connection. So far the car is coming along nicely, but it feels like hitting a brick wall just before the finish. Car is in mint condition..keeping up the good spirit, I will drive it into Paris in the spring.

Cheers, Tom

[Cadman-iac]

  I'm confused then. What does that connector your showing actually plug into? Another connector?
If it is connected directly to your printed circuit board, then it should be going into an opening in the back of the cluster, making contact as it goes through the printed circuit board. The circuit board should have an opening in the exact same place as the cluster housing. Unless the 67 is much different than a 69 is.
I'm going by what I remember about the 69 I used to own 33 years ago. My memory might be more fuzzy than I thought if I'm that far off about this.

[TomB]

Hereby a picture of the opening in the circuit, the 12 pins terminal/connector, slides in and locks ok(I guess). The description in de shopmanual describes the 12 pins nicely, 11 have a clear purpose (no ground}, one is has no purpose and has no copper strip on the board, helps me to be convinced that I am not putting the connector upside down. By the way, none of the pins communicate with the climate control, lights or wiper. Obviously no crevice for the shoulder on the connector.

Am I overlooking something?

[Cadman-iac]

  Tom, to me it sounds like you have a broken power supply path in the circuit board, because only half of the cluster is working. I also noticed that the circuit board has 12 connections where it plugs into the harness. Could you be missing a wire in your terminal block maybe?
You must have a good ground point somewhere for your cluster, because half of it functions.
  If you can remove it from the dash once again without too much trouble, I  would suggest that you trace each of the circuits on the board visually, but then also check each one with a multimeter for continuity.
The lights for dash illumination are on one circuit, but may be split between both sides of the cluster, so you could have 1 or 2 power circuits for those. Your turn signal indicators will be separate power circuits as well.
Which gages are functional and which are not? You don't say. And what lights are working, which ones are not?

Another thing that you can check is if you have power coming to your connector terminals. If you can identify which ones are which, then you can check for power when the accessory or switch or whatever is turned on. If this all checks out, then you will at least know that the issue is with the cluster itself. Either with a ground point, or a power path. Also check out the bulbs themselves and make sure that they are not burned out. You could be chasing gremlins for nothing if the bulbs are bad.

[TomB]

More options to check, really appreciate your steer. All bulbs are new and just ordered an NOS flexible circuit board. Fuel gage and tempgage are stuck at max, only generator and brake light up when making ccontact. Will take dash out tomorrow to probe the terminals and seek ground point. Rule of thumb I learned is that bad ground is 95 pct of the causes when it concerns electricity. I ll keep you posted, thanks a million.

[fishnjim]

If there's copper under where the attaching screws go, that'll likely be the ground(s).   Most automotive doesn't have a separate ground unless it fiberglass or plastic.   They tend to ground through the body.
Could be a broken connection on the board on one half.  Look at the board connectors and determine if there's two circuits or individual.  Follow the copper strips.   You have to "ring out" each pin one by one to where it terminates for continuity checks.
They did it this way so not to have a bunch of wires dangling and the reduce time it takes to assemble.   Pre-war they used wires.   It goes back a decade or more.   Early days of plug and play circuit boards.   They tend to delaminate and corrode over time.   I'm not sure if anyone's making the '67 boards.   
I found repro ones for my '58, but repaired the original and it works.  You can solder over the copper if you carefully remove the insulating top coating.   A circuit board shop or maker can make or repair.   You'll find a lot of issue with the old wiring, too, as it's probably brittle and prone to corrode inside after that many years.   You can't see under the harness tape, but it can be ugly under those wrappings.

[TomB]

A couple of ground wires from the screws attaching the printed circuit to the firewall did the trick. 9 out of 10 is indeed grounding....Thanks for all the tips and tricks.