'79 Speedo not working

[Rupesy]

Well since I bought the car, the speedometer has not worked. I have just been using a GPS for reference. I decided to take the winter months to figure this one out. After doing some research on a few websites and forums, I found out that the issues can be with with the sending unit, corroded connection in the spare tire compartment, cruise control, or printed circuit board. My speedometer, odometer, and cruise control do not work. I decided to start with the sending unit. Directions I found said to use and ohm meter and rotate one of the the tires and it should open and close a few times a revolution. I hooked up my meter and found it to be working. Thought I would post a picture for reference and I post follow ups as I work my way through the problem.



Next I am going to test the terminal connection at the CE panel to see if I have a signal that far and work from there. Supposed to be terminal T1 and T2. I'll post back my findings.

Let me know if anyone has additional suggestions.

[garylewa]

Check the printed circuit board.....95% sure your problem is with the board

[Rupesy]

Ok, finished checking at the CE panel and it looks good up to this point. Gary, looks like I will be checking the circuit board....

[Maleficio]

It's definitely the board. I found several terminal screws totally backed out on mine from a local shop that fixed the lighting for the PO. Ran them in, all gauges work great. Hopefully you'll be as lucky.

[Pete R]

my board had a hairline crack in it. When I was driving I could reach under the dash and touch parts that made it start working again

[Landseer]

Good methodology. thanks.

[Maleficio]

Sounds like the connector on my ignition switch. I can reach under and wiggle it making the stereo shut off. Need to pull and tighten/compress the terminals.

[Mrmerlin]

Mal replace the ignition switch,
or you might just let the smoke out of your ignition harness

[Maleficio]

Mal replace the ignition switch,

or you might just let the smoke out of your ignition harness

But it only affects the stereo. I csn induce the gripe by wiggling the connector.

[Pete R]

poor connection = resistance = heat = smoke= fire

[Maleficio]

Haha

[Maleficio]

Oh, you fear mongerers!!

[Pete R]

When I bought my car half the electrical stuff didn't work. The more I drove it the more stuff started to work. So I do the same thing.. that was our legal disclaimer, besides that's what fuses are for.

[Maleficio]

Yep, they've got to wake up, and WD-40 helps this process.

[Rupesy]

Finally got the gage pod removed (not too bad of a job) and it revealed some interesting things. The first thing I noticed was that a connector was kind of dangling from the pod, although still hooked up to the circuit board (Wow). It looks like the plastic broke and they tried to use a piece of an old computer circuit board for a cheap fix. This is the speedometer connector and turn signal light connector which are both not working. It is interesting to note that the speedometer is the last connection on one end and the turn signal is the last connection on the other end. The copper connections do not seem to have a good support under them (lousy circuit board fix) to make a good connection so I am hoping that this is all that the problem is. Also found a soldered in wire, but it works just fine. I don't have any other issues that I know of, but I plan on just doing some continuity and light bulb testing anyway. Do I have to buy the bulbs somewhere special or just at any car parts store??

[garylewa]

Ohhhh, that looks familiar! I'm glad you found what looks to be the problem. I will offer you another piece of advice. Buy a new printed circuit board from 928 INTL for ~100.00 clams.

My reasoning (short story version): You are going to remove the cluster, clean everything up, check continuity (it will pass, believe me), re-install it and the speedo probably still won't work . Then, you will repeat this same order of operations many times (I did this as well as new soldering for a couple of weeks straight to "fix" my speedo problem). this thing will defy all laws of electricity. I even had my cluster bench tested by someone that I deem an electronic whiz (PhD EE); he even stated it should work; it didn't . I bought new speedo's and tach's; they didn't work either. By this time I invested so much time and money into this cluster problem I had to solve it. My wife thought I was nuts.
All hope was restored when I found someone selling an '83 cluster on the internet (not eBay). I bought it, installed it and happy, happy, joy, joy!
The Porsche paper circuit board is one of the worst damn inventions I have ever seen in my life. Make your life easier and spend the money for a new board.

[tmpusfugit]

He needs more than a new circuit board. The plastic housing should have extensions that the circuit board folds over and there should be a black plastic piece on each connection that locks the connection together. I will try to post a photo or 2 later today showing details...one of the black plastic retainers can be seen on the laast photo, all 3 connectors should have these, otherwise, many problems...

and you are very correct, this is a very poor method to connect electrical devices...starts out OK but over time and repeated disconnects/reconnects the stuff ages and becomes brittle and fails....

[Pete R]

Someone has already put a new board in it once. The original ones were brown.(not sayin you don't need a new another new one) The tabs must be a common failure, Mine looks exactly the same. I've had the tabs "hangin" for 20 years. When I put a new board in I couldn't find a new back to the cluster. So I just had to roll with it. Still working ok.

[garylewa]

Originally Posted by tmpusfugit

He needs more than a new circuit board. The plastic housing should have extensions that the circuit board folds over and there should be a black plastic piece on each connection that locks the connection together. I will try to post a photo or 2 later today showing details...one of the black plastic retainers can be seen on the laast photo, all 3 connectors should have these, otherwise, many problems...

and you are very correct, this is a very poor method to connect electrical devices...starts out OK but over time and repeated disconnects/reconnects the stuff ages and becomes brittle and fails....

Yeah, I'm looking at the photos and you are correct! He is missing the connectors. Good call!! How's your resto going??

I have cannabalized three instrument clusters so if he needs any parts he can post here or PM me and we exchange info.

[tmpusfugit]

One thing to keep in mind, I believe that starting with MY '83 the clusters moved from 12 pin connectors to 14 pin connectors so the clusters are somewhat year dependent. I have both a very poor '81 with broken off plastic guide parts as well as a very good '84 that I got from Mark Benton for a very reasonable amount of $$. I think '82 back to '78 are generally pretty much interchangeable, at least as far as all the major functions go. I understand some 5 speed cars have a shift warning light(?) and Euros may also differ? My '81 was a 5 speed and all the others have been autos so what I know for certain is very limited...like maybe the sun will rise tomorrow, all else is speculation on my part...

Regards my resto efforts, one car scrapped, one car on the road running well and sold, and the 3rd car is licensed and inspected, but currently have a leak in the vac line to the transmission so it is up on stands awaiting dropping the exhaust and heat shields to find said disconnect.

PO's mechanic really did some crap work.....bad rear wheel bearing now replaced, axle nut on bad WB was finger tight, as was new starter mounting bolts, flex plate to drive shaft coupling was torqued to about 5 '#'s, all lug nuts were finger tight, 2 directional tires were running the wrong direction, the Boden tube retainer was on the wrong side of the bracket, the kickdown cable was entirely hosed leading to no more than 1/3rd throttle possible.etc...etc....

The good news, I have the gremlins out of the cluster, the interior of the transmission looks like it is all new, the engine runs very solid, it has a new TT, new alternator (also with finger tight bolts), very clean, new dual exhausts with Holley glass packs (loud) etc etc...the interior has cleaned up great, with a few interior parts from Mark Benton as well as fellow Pelican listers as well as some from Renn.....as I recall I got the dash and pod from you Gary did I not? Thanks on that one, big time....a big help to me!