battery warning light

while driving I had my tach go to 0 and at the same time my battery light illuminated. The truck stayed running along with the accessories (A/C, radio< Windshield wipers etc) but it seemed very sluggish. Any help would be great.
Thx
Robert

Rob, does the vehicle start right up after being turned off? Sounds like a alternator or battery problem. Did you go through any big puddles or anything. let me know- Rusty Owens

It starts right up and runs normal. The wipers were slow and it seemed sluggish but that's all. I haven't gone throgh any puddles or anything. What seemed strange is that my RPM gauge is reading 0.
I also took the Battery out verfiied the water level and installed it in another vehicle. I let it run for about 15 minutes or so with no problems. I reinstalled it in the Disco and still had the light and no tach.

It can be as simple as a broken cable up to a knackered alternator.

The rev counter will work off the back of the alternator, hence why your rev counter has stopped working.

Check the cables at the back of the alternator, check that they have not broken away, and check for corrision. If you have a volt meter, clip it on the back of the alternator and run the engine, you should get a reading in the region of about 12 to 14v, (14v with a few revs..

If less than 12V, then your alternator has had it, and time to replace. This is a relatively easy job, only three bolts.

easy job but a bit pricey for an alternator. Thanks for the info on the rev counter (Tach) I will look into that. I do have a volt meter but not on hand so I will check it ASAP

for anyone that wants to know I had the alternator checked and it was bad. I ordered a new one for $214. Not to bad