could my troubles be from not having my tach sensor hooked up? does the alt sense anything from the tach to decide when to turn on or off?

 

yeah... i've heard that it uses tach signal to let the pcm to charge... has to know the engine is turning b4 it can excite the fields. why dont you have the tach sensor hooked up?

 

my tach riped out when i pulled the head. now i have tried hooking it up every which way u can with the three wires and it wont work. i have the center wire hooked because its the one i know is correct but switching the other 2 wires nothing happens.

i got the alternator to work tho by doing the thing RSWORDS posted and it cranks 15 volts about.

i still think the comp is toast tho unless that tach sensor is giving me trouble because my AC doesn't work, and my cruse control wont work on top of the alt not charging untill i did the fix on it. ill prob start another post to see what everyone thinks on that tach sensor controling the entire computer or not.

 

look at the plug in that goes in the alt, the wires on the male end , see if they are broke at the plug, i had the same prob and went through two alts and had both of them checked and they were good, but i found that the wires were broke inside the plug ,,HOPE that helps

 

well your tach sensor is shafting the operation of your PCM... go buy a $20 haynes manual... and a new tach snesor if it isnt too much... your alt may start charging but your cruise and A/C will work again for sure... the PCM has to see the engine spinning b4 it'll execute any of those commands

 

well 94cummins12v unplugged his sensor and said his alt was still charging fine and his ac still worked the only thing that changed was his tach wouldn't work. he has the same truck as me. im sure that my computer isnt working but im not sure if it is because it doesn't sense the truck running or if the computer is just toasted. where else could the computer be getting the info that the truck is running other than from the crank pos sensor?

 

how about my speedo being way off? tach being way off? not charging?

 

i still havent found my problem out. im putting in a tach sensor as soon as it gets here in the mail to see if that is what my comp is reading off of and if its still not working im gonna buy a used computer and that will hopefully solve my problem.

what have you tried to fix your problem?

 

nothin yet...just got the truck and have been focused on some other non electrical things. keep me up to date and ill do the same for you

 

all my problems solved it was the crank position sensor/tach sensor