1999 S10 Blazer- after disconnecting battery and letting car sit for a while speedometer 'pegs" at full scale. Battery is disconnected as car will sit for 30 + days without being driven. Reconnecting battery does not bring needle back to rest. Sometimes after reconnecting and driving speedo will come back to normal. Other gauges work normally.

 

It sounds like your cluster is on the fritz. It isn't all that uncommon for the stepper motor inside the cluster to go wonky. But you should verify the VSS signal and speed reading that the PCM is seeing first to make sure that it is a cluster issue.

Once you have confirmed that the cluster is at fault, you can decide whether you want to tackle the replacement of the stepper motor your self, have someone rebuild your cluster for you, or replace the cluster with a used unit (which I believe will require the cluster to be programmed with your mileage).

 

Thanks. Gut feel was cluster problem but hoping for easier fix.

 

I am trying to locate stepper motors for '99 speedometer repair. Any leads on who may have for sale? I dont want to replace entire instrument cluster. Thanks

 

eBay has a ton of stepper motor listings. I haven't looked into the availability of stepper motors for the s-series trucks though.