The other night I was about 130 miles from home and my alt quit charging. so I changed the alt at A autozone parking lot. but still not charging. I carged the batteries zipped tyed the fuel pump. went home. also the tach has been erattic too for awile. I dont want to just money at it. that dont fix nothing any insite will help thanks

 

I'd check wiring and if OK, pull alten and return. Perhaps AutoZone has a method to test while you look?

 

I did this morning the alt is good. I got A dodge service book for that truck. The book says the alt field goes thru the AST relay& crank sensor. The ecm regulates voltage. The wires are good up to the ecm. With A scanner IM not getting A rpm signal. I got the sensor off and going to find out good vrs bad. I wish the truck was standard Id do away with all that and go old school like the old chevys.

 

change the crank sensor, if its not reading it wont charge... it runs the ASD (automatic shut down relay) it controls the alt, along with a few other things, with no tach signal, it doesnt work

 

thanks. I read that somewhere. I got A snapon soalics scanner&vantagepro multimeter. But the vantage wont configure scnd gen cummings It will configure 3rd gen an the new 6.7 My dealer cant tell me why. Snapon wont call me back. The sensor will be here tommarow. I hope that cures the problem. A new ecm Is right at 500 from the dealer. My scanner will go to function test and make the relays turn on & off. One one test is to check gen field, It makes the ASD relay turn on and stay on but still nothing at the alt. The trucks got 330000 on it but still runs fine. I dont wont to spend much. Next year I was going to upgrade to A 4wd and 6spd trans but folks are proud of them here. thanks again

 

Without a wiring diagram it is difficult to comment, but do you see voltage being sent back to the alt field?

How did you confirm the alt as being OK?

 

I'll agree with dodgetrucker on this one.

Change the crank sensor.