1997 Blazer s10

I have a fuse blowing that is a 10amp in the gauge slot of the panel.

I suddenly lost the speedometer and tach as well as the amperage gauge. (what's the relation?)

The result is the alternator not charging the battery.

I've brought in an electrical trouble shooter and determined it's not the alternator wiring.

I had a new trans put in 3 months ago and then moved 3000 miles away. I had some leaking problem around somes sensors and it worked on under warranty.

I was told by the original installer it could be the Neutral safety switch or Range switch. Which sensor picks up the speedo and the tach? I got the feeling from talking to some it could be almost any sensor.

Where would you start? What else runs off that fuse?

Any help would be sincerely appreciated.

 

The speedo is controlled by the VSS (vehicle speed sensor) which is on the output side of the t-case (4wdr) or tranny (2wdr). Yours should be wires and not a cable. Check to make sure the wires are not pinched or shorting out.

The tach is controlled by the distriburator. Check the wiring, it is under the cap and rotor. Could be the module that picks up the signal is causeing your problem, or the wiring.

The tach and speedo are not related in any way, except they might be on the same fuse. They operate independent of each other and might share the same power supply. That would be the extend of the commonality of the tach and speedo, they share the same fuse.

Your problem may lie in the alternator circuit. There is a wire connected to the post on the back of the alternator, actually should be 2 wires connected to that post. One of the wires has a fuseable link within 12" of the post and provides power to the truck when the engine is running. The battery idiot light on the dash will tell you if you have an alternator problem via the wiring harness on the alternator. If there is a problem with the charging circuit the idiot light will come on and stay on. The second wire runs to the battery and is how the battery is charged while the engine is running. On newer trucks there might be one wire that runs to the under hood fuse box, from the underhood fuse box the path is split and one wire powers the cab, while the other wire runs to the battery.

The battery has a wire that runs to the engine, to the frame, and there should be a wire from the body to the engine behind the block, look for the wire on the firewall in the engine compartment. Should be the black wire on the battery. Make sure there is no corrsoion on any of the connections and that the wires are in good shape. Ground side of the battery.
The other wire on the battery runs to the starter and alternator/underhood fuse panel. There should be two wires on the same starter post as the wire from the battery. This second wire runs to the cab of the truck and provides power to everything when the engine isn't running, although with the newer trucks this wire might run to the under hood fuse panel. Should be a fuseable link within 12" of the starter.

Now for the voltage gauge, this reads the amount of charge in the battery. This is not related to the alternator directly. The voltage gauge shows how much juice the battery has, not how much the alternator is pushing out. The idiot light is the only clue of alternator power.

I do not know if the voltage guage is tied into the same fuse as the speedo and tach. I would have to check my Chilton manual to verify, and can do that tonight if you would like.

Where specifically your problem lies, hard to tell. I would disconnect the VSS wiring and see if the fuse doesn't blow out first. Then disconnect the distribuator next. By eliminating them one by one you can narrow down where the problem lies. Post up what you find out.

 

Disconnect the VSS at the t-case or tranny by pulling the electrical conector off. On the t-case the wiring is next to the rear driveshaft. On the tranny is it also next to the rear driveshaft.

The wiring harness for the distrurator is behind the distriburator, this can be a real pain in the butt to work with, much easier to disconnect the VSS first.

I don't think you can disconnect the voltage guage without killing power to the cab of the truck. I believe the gauge reads power off the main wire to teh cab via the starter. No way I would disconnect the starter with the battery hooked up, and no way I would disconnect the battery with teh engine running.

 

did you ever figure out what the problem was mine is doing the same thing