I have a 2000 4dr 4x4 S10 blazer. I have been having what I would call some weird electrical issues. fuel gauge is stuck on E (I just replaced pump and sending unit and its still stuck on E) connections all seem to be fine. 2nd, in park with engine running, when I rev the engine the spedo will jump as high as 5mph. 3rd, if I sit with the engine of and my stereo on for any more than about 5 min I cant start it the battery will be dead, but my truck starts fine every morning. when I measure output of my alternator it reads only 13.5v (load or no load). I tried to jump my truck a few minutes ago and when I did my fuel gauge went to full for about 30 seconds and then back to E. In my experience most alternators should put out between 14.2v and 15v. yes my belt is tight.

suggestions???????

 

Load test the battery with the proper tool or take it to a parts store and have them test it

 

I second motion to test the battery. 13.5V out of the alternator isn't bad but it isn't great, either. Test the battery and if it's bad, re-test the alternator after replacing. Can't hurt to upgrade while you're at it; The stereo in my 2000 caused a few gremlins in the battery and alt, replaced with Optima and an alternator for a 2003 (I think, maybe 02-03) which has a little more power, problem solved. Also note that these cars are poorly grounded at the factory. You may have to add another ground strap or two....

 

Yea, Battery. I just had a battery from NAPA that I bought in December for my 86 F250 4x4 460. a few months ago it would be dead if I didn't start the truck every couple of days. (This truck has NO ELECTRICAL PROBLEMS. I keep this truck in top shape all the time because it pulls our 10,000# travel Trailer.) I took the battery to NAPA & it checked OK. But they replaced it & the trouble ended. My alternator with the battery they replaced would show 13.2 V with head lights on about 12.7 V. With the new battery the alternator charges 14.2 V period. My thought was some of these batteries have shorts inside not letting them take a charged.