If the speedometer is not working but the odometer is, I would suspect the dash cluster is at fault. If both speedometer and odometer are not working I would suspect the speed sensor on the transmission is at fault.
If both the speedometer and the odometer work on and off, I would blame the vehicle speed sensor. If only the speedometer is acting up, I would blame the cluster.
The lights on the odometer on a 1999 Chevy Blazer might not work because of a burned out fuse. They might also not work if the lights are burned out.
I believe that the first digital cluster on a S-10 Blazer was in 1989.
Need to figure out what's wrong with them, first.
unhook it from the speedometer head and unhook it from the tranny and take it out.
i had this same problem, it was the headlight switch, cost about 30 bucks in a 2002. it also messed with the navigation system
If both the odometer and the speedometer do not work it may be the speed sensor in the transmission is bad. If only the odometer does not work it is probably a bad cluster.
Left side of the where the speedometer is there will be a panel you can remove and there will be where the fuses are
If it is electronic (not cable driven) and both the speedometer and odometer are not working I would suspect the VSS (Vehicle Speed Sensor) is faulty. The VSS can be found on the tail end of the transmission. If only the speedometer doesn't work I would suspect the dash cluster has to be replaced with a new or good used one. Really need to know what year S10 Blazer you have.