My wife took our 1996 Ram 1500 to the airport the other day to pick up the in-laws. As far as she can remember, nothing unusual happened from the time she started the truck at home until she parked it at the airport. When she went to leave the airport, the truck would not turn over. Windows and other accessories worked, albeit a bit slowly. AAA came and provided a jump, but the the truck would cut out if it dropped below approx. 1500 rpms. On the way home, the generator light went on and off. The truck is now home, and I need to troubleshoot. I was thinking alternator, but I can't imagine that it would be the cause of such a sudden and dramatic failure. I was thinking instead that maybe it has something to do with the coil or the Powertrain Control Module, but I honestly don't have a clue. Suggestions, please!!

 

I would check for parasitic draw as well as the alternator, to check for parasitic draw take the negative cable off the battery and take a DVOM (Digital Volt Ohm Meter) and put the negative lead on the negative terminal and positive lead on the negative cable and turn the truck on, record the voltage and then turn it off and record the voltage.

It could be a combination of the Parasitic draw and bad alternator, bad alternator not charging the battery and a draw taking voltage away enough to not be enough to start the truck.

 

i had one one time that had same symptoms, had it in the shop for a couple days.

cust didnt want to replace alternator because he said it was new btw

i finally ended up leaving my Fluke on it overnight and letting it record the voltage through the positive cable directly to alternator and found out it was losing power thru it

i took alternator apart(so called remanufactured) and found that the brushes were tore slam up and had melted into the stator andwindings and eveywhere else and was just a HUGE mess

tested parasitic loss again with one i had laying around the shop.
and it was fine!

replaced alternator - good to go!

yes it could actually be the PCM

or something as simple as a Bad battery or an interior light - glovebox maybe left on

an alternator DOES NOT WORK if your battery is dead

an alternator NEEDS voltage to make voltage

so there is a good chance it could also be your battery.
the truck cannot make enough current at idle to keep truck running.

test your battery - charge it back up first
test for parasitic loss
if good, test your alternator

 

I feel good when after I post help to a problem, you (XXL 1500) post the same thing haha, it reassures me.

 

You can take the alt and the battery to advance auto parts if you got one near you and have them test it....

 

yup
they seem to be pretty reliable

 

Not sure where you are located, but here in Oregon there are several shops that will let you drive your car into their parking lot, and they will wheel out a machine that will test your battery and your alternator/generator. The best thing is - they do it for FREE! The stores that I have used to do this in the past are Autozone, Napa (I think), and Les Schwabb tires. Not sure if you have something similar in your area - but if you go to a local auto parts store and ask, I'm sure you'll be pleasantly suprised.

If I had to guess... I would say your alternator is on it's way out.After a jumpstart,your alternator should be able to provide enough charge power to keep the truck running.

Good luck!
Cartman