Racing_Joe66

then i lost my speedo and tach at the same time. i am stranded in Clarion, PA. the battery's tested fine but low on juice from the alt not charging them. but the alt was bench tested and it says its fine. just not getting anything to the batterys.

help

vzdude

Check the 150 amp fues in the underhood fuse box. The terminal on the back of the alt. gets hit many times when changing the oil with a filter wrench and that blows the fuse. It is held in the fuse box with 2 bolts and cost about 10 bucks!

infidel

Sounds like your engine speed sensor or the wiring to it has failed.
The ESS is located at the engine front lower pulley, wiring runs upward.
Sometimes it can get nicked by the fan or the connector to it dirty.

vzdude

BTW the speedo works off of the ABS sensors and that computer is very sensitive to voltage. Speedo quit when the voltage got too low for the Antilock module to work right. Infidel is right too, could be the crank sensor/ESS or wiring.

Racing_Joe66

stopped had 1 battery checked out and they said it was good so they charged it. checked the alt on bench it was good. so checked the other battery and they said it was bad so we put everything back in but that alt and everything was good to go. about 800 miles from home and the same thing happened with the other battery. so i bought 2 new batteries and it didn't fix the problem. this is the 4th time in the past month this has happened.

the sensors are all fine as are the fuses. so it must be the regulator inside the computer acting up??

let me know what u guys think.

wannadiesel

Check the wiring to the crank sensor very carefully. That is a much more common problem than the PCM dying.

Racing_Joe66

ok. after we had the alt checked out fine and then the 1 battery was bad and the other good we had the good one charged an stuck it on the truck. fired the truck up with the 1 battery and it was charging again. so we hit the road and the next morning it starting doing it again the volts gauge started dropping.

so we stopped and i bought 2 new batterys. the volts stayed around 12.6 for most of the way back home and we had 800 miles to go yet. got home and the volts gauge was down to 7.4-7.8 volts.

i let the truck sit a couple days and i went out and i jump started it and the volts gauge went back to 13.4-13.8 volts. drove 2 miles to my shop and was checking stuff with the volts meter and everything was fine then all of a sudden the volts dropped to 11.4-11.6 volts.

the heater grids aren't on at all. i checked them. there is power at 1 of the terminals on the ALT and there is power coming out of the ALT. and there is power coming from the 120 amp fuse to the battery.

so it is charging but something intermittly is draining the power and where the ALT can't keep up.

or could it be the ALT????

i have had it benched tested twice while on the road when it was acting up and both times tested fine at 13.8 volts.

what do u guys think??

need help fast.

thanks