Speedometer shorted?

[gmoney]

I just replaced my heater core and while I had the dash of changed the bulbs in the gauges. I put everything back together and the heater core works great, the only problem is that when I turn the key to the "on" position, the speedometer needle goes to 20, and while driving it stays between 30 and 40 no matter how fast I go. The rest of the gauges seem to work fine. So does the cruise control. I heard that maybe when I plugged the gauges back in i might have crimped a wire or something but I tried plugging it back in and no difference. Any ideas what happened?

[deevergote]

Either you pulled, pinched, or otherwise damaged a wire while pulling the dash... OR your VSS is going bad. That, or the cluster itself is failing. That happens occasionally.

The easiest thing to do is to replace the VSS. It's probably original anyway, so replacing it won't be a bad thing, even if it's not the cause of this particular problem. Next would be to yank the dash again and inspect all the wiring. If all that checks out, try another cluster. If a new cluster has the same problem, and the VSS is new, then you can be certain it's in the wiring somewhere.

[Fleetw00d]

If the cruise control works correctly (and if the odometer works correctly as well) it is not the VSS. I had a problem with corrosion on the printed circuit board in my CB9 that caused erratic behavior of the speedo and odo. Replaced the PCB with a non-corroded one (from a sedan so I had to change the speedo as well), fixed the problem. I suspect you damaged the wiring.

[batever]

The most obvious approach in cases where something appears after you do a repair is to always look at what you did right before the problem occurred. In this case, you removed the cluster. So something you affected by removing the cluster most likely resulted in the symptoms you are experiencing. Things you affected : 1) you physically moved the cluster and the gauges in general. it is possible they could have been damaged in that move. 2) you affected/moved the wiring as well.

Your two possibilities are damaged/altered wires or electrical contacts, or a damaged gauge.

An answer outside of this system of assessment would be a damaged vss. You didn't directly do anything to the vss so it seems unlikely, but the vss could have taken this moment to take a dump, so to speak. But I would look at other causes first because that seems unlikely that it would choose this moment to act up, when you haven't even touched it during your work. You could have, however, pulled on the wiring in a way that affected the speedometer.

From a more fundamental level, it would be good to figure out what kind of electrical input would cause the speedo to start at 20 mph and top out at 40 mph. Then try and figure out how what you did could have caused that kind of input.

Knowing little about speedometers or the cluster in general, i can't really help you further than that.

good luck.

[gmoney]

Thanks for the input. The only thing that makes me think I might have damaged the vss is I turned the key to the "on" position when the cluster was removed. Could this have shorted the vss? However, it is unlikely since the cruise control and odometer still work.

Any ideas on how to test the circuitry on the speedo?

[TheNextEpisode]

Jeez. Every response in this thread was solid. Can't we lower the bar here a little bit??

I'm having a similar problem that I've been too lazy to diagnose. This is good motivation to get on it. Good stuff guys.