Hi,
I've gotten quite a bit of help here with my dead cluster and have dug into it quite a ways but I need a reality check.

Here is what I know:
1) All dash warning lights and gauges are dead. The OD indicator arrow is on and will switch off when the button in the shifter is pushed but this setting is not retained when key is turned off. Fuel and temp gauges are also dead.
2) Car starts and runs normally. Starting the car doesn't get any of the lights or gauges to work consistently. The "battery" light for the charge system has come on a few times but not consistently. It seemed kind of "flickery". It currently is not coming on.
3) Autozone's test machine says alternator (including voltage regulator) is fine.
4) I have power at the blue wire in the three wire connector at the back of the speedometer when the ignition switch is on. Current is getting from this connector to the circuit board it connects to.

Here's what I am thinking. Please let me know if I am missing something or am off track. I'm getting better at figuring out my Bentley wiring diagram but am not good yet.
1) Since both the gauges (fuel and temp) and the warning lights are dead, I've ruled out problems with the grounding system through the alternator. As best I can tell, the gauges ground through their senders so it doesn't seem like problems at the alternator would shut them down too.
2) This leads me to suspect a problem on the supply side, but as I said, current is coming in on the blue wire to the speedometer and appears to be getting to at least the connector on the circuit board. Is there another wire I should be checking for power coming in?
2) I'm beginning to wonder whether there is some kind of problem within the cluster that is interrupting the current. Are there any common failure points internally?

Thanks for your help and patience with this. It's beginning to get frustrating.

Is the 3-wire connector with red, blue, and black wires coming to it connected to the speedo well? If it's loose, it will cause the cluster to go dead and the "charge" light to act wierd.


-b.

There's a sneaky fuse in the cluster made of a thin strip of flexible circuit fastened between two screws immediately above the speedometer on the back of the cluster circuit board. You should have +12 on BOTH of those screws. This is the only fire protection, as the wire feeding the back of the speedo circuit board is not fused anywhere else.


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Art Benstein near Baltimore

Thanks! I took a quick look at that strip this morning. Visually it appears ok and I'm reading something like 60 ohms across it. I don't have the cluster wired up right now to check the voltage.

The interesting check is that I have an open circuit between the connector for the blue wire coming in and both of the screws. This doesn't seem right unless the screws are fed from the voltage regulator or something similar. I haven't had a chance to dig into the diagrams and won't before I have to go to work.

Any input? I'm thinking I need to open it up tonight and start tracing stuff but want to make sure I'm on the right track before starting in.

Input? Sure.

It traces directly from the speedo's board edge connector to the speedo's row of three berg stix mating with the cluster board. Only place it goes on the speedo board.

On the cluster board, the end of that row of three joins one side of the flex fuse (brass ring lug). Other end of flex fuse feeds back through berg stix to speedo, as well as runs around the cluster for gauges and lamps.

You can trace it all by flipping between these two images of an '89's cluster:

back
front

Some notes on the electronic speedo
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Art Benstein near Baltimore

Hi Art,
Thanks so much for the help. The notes and diagram were especially helpful.

Here's what it was. I didn't have continuity between the first (bottom) pin on the board and the brass lug that the flex fuse attaches to. I took the fuse off and suddenly had continuity. I couldn't find any problems with close inspection but I went ahead and resoldered the joint where the lug appeared to attach to the pin. Everything seems peachy now- I guess time will tell if the solder repair is permanent but at least next time I'll save about 3 days of troubleshooting.

Thanks again for all your help with this. The info you provided was invaluable and I'm not sure I would have gotten it figured out without your help.

Lyle

You're welcome, and thanks for the details of the failure point. We've all fixed a lot of solder joints come loose on these cars, but that one - on the brass ring lug - is a new one on me. Your feedback will help someone else.
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Art Benstein near Baltimore