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Hi,
Interesting that he brought up the idea that there is some sort of automatic circuit breaker built into the circuit board on the cluster. This I do not think so!
The brains to do such a thing are not on that circuit board. It might be in the ECU, if this year cluster even talks to the ECU. I don't think that started until 1992 and may have more to do with idling or timing, I have read.
There is a fuse strip, made out of circuit trace material, that fits right over the top of the speedometers white housing. It is held down by two screws at each end.
Sometimes people who do the service work, like you did, remove those screws inadvertently when removing the backside from the black housing.
If this is done it will cause some things like idiot lights or the charging function until you make sure the strip is put back tight.
I can, on most occasions, see the speedometer needle jump up when first starting the engine but it's not very far up, maybe up ten mile per hour. I have always written it off to the electronics or the speedometer electrics first getting its jolt of juice when coming on line.
Yours does seem to be excessive. On new cars some do that to impress somebody? Not me, I see it as wear!
When you say something about the tachometer, is this one built into the cluster itself and is as big as those with a clock in that spot? You did not say if it was still working now as usual? Just it was before the tear down.
There is a white wire with a red stripe that you have to be careful with. It goes only to a tachometer and no where else on the cluster! If you plug it on the cluster it can fry the speedometer.
This white/red comes from the ignition coil and it is run loosely out of the normal wiring loom. It is to be used only the small diameter tachometers mounted to the right of the cluster as it easily reaches that far over. Thus is not saying it can't be used elsewhere.
I have never owned the large tachometer cluster so it do not know how those are wired. The big clock gets its power off the circuit board through wired up plastic towers on the board that have 12 volts on all the time.
Double check what wires really go into that left area! Don't put anything on those double prongs ones, near the speedometer. They usually have a piece off rubber hose on them to stop you.
The tachometer must have a separate power system that goes off with the key switch and possibly that wild white/red wire on goes to the negative terminal on the tachometer. Don't hold me to that!
Maybe you have got something in the wrong place despite your best efforts!
I have learned its better to take pictures unless it's a one hour turn-around job!
There is a single yellow or a yellow/red that only goes to one bottom corner of the cluster. A shift up arrow light maybe ? I don't know what it does but as I remember its non-insulated terminal on the end, as where as the White/Red has a plastic tipped end on it.
For all I know, if the White/red gets grounded, it might kill the engine.
If I'm not using a small tachometer, I keep black tape on it, so I will not hook it to anything!
I still have one car that I will be putting a small tachometer and voltmeter into soon.
I was into the dash, not long ago, for a non-working clock and I also put in a new odometer gear ahead of it crashing.
I still put some tape on the loose wire to keep that snake from biting me!
If I go to remove black tape off of something, I'm suppose to think, Why is it on here?
Habit from working with High Voltage AC, it might be a hot wire! This works for me anyways!
Again, It has been mistakenly used before and has harmed a many of our Brickboarder's speedometer clusters.
Phil
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