zookeeper

I am having problems with my alternator - it pulsates. It will charge then not charge. I've replaced the alternator as the old one quit charging. Now, on the second new one and you can watch the guage bounce back and forth between 8v and 14v. Thought the voltage regulator was faulty on the first new one but this latest one does the same thing.

Its on the 97 Ram 2500 in my signature. Any thoughs or suggestions on what I can look for?

madhat

Is it in the morning when the truck is cold? It could be the grid heaters.

zookeeper

I thought that too, but the alternator is changing from charging to "battery" and would think the grid heaters would pull whether it was from battery or the alternator. This is like it cuts out charging alltogether - not just a load on the system.

zookeeper

This is new news to me and I was told there is a generator relay circuit between the alternator and the computer. This relay supposedly turns on and off the voltage regulator in the alternator.

I thought the 97 was mechanical and didn't depend or work with a computer. Now I'm being told it is most probably the computer that controls this generator relay.

Any idea on how much a computer costs???

rebal

might be the crank senser

mechmagcn

Check your chassis grounds, a corroded ground will cause the regulator to pulse.

zookeeper

Thanks, as an update - the repair shop stated they thought it was the computer. As they tried to verify - the truck quit displaying the symptoms. Either way, they said the computer replacement would be almost $800 installed and the computer is on national backorder. The shop was great though. They did the diagosis all afternoon and didn't charge me anything.

I plan on checking the crank sensor (maybe replace it as a precaution if the cost is not prohibitive) as well as the chassis grounds this weekend. Somehow I feel it has to be something like that verses the computer. Like I said, last night, it quit pulsating and is charging as it should. It has become an intermittent problem which is a pain to track down.

I don't want to continue to "change this" or "replace that" as it is expensive but don't want to leave the wife stranded with a vehicle that doesn't start either.

Thanks for all the advice so far - keep it coming and I will keep you updated on the outcome.

mini14

the charging system is controled by the pcm on the firewall, a quick easy cheap fix is to bypass the pcm and add an external voltage regulator. if u use the search function search external voltage regulator you will have info....its a $30 fix at most.

zookeeper

I sincerely appreciate everyone's help and suggestions. Although I don't post here a lot, I feel like I know a lot of you and the knowledge shared here is invaluable.

No issues this weekend and the alternator seems to be working properly (for now). My plans are to go ahead and clean all the chassis ground points. I am hopeing to wait till the weather gets a bit more decent as I am going to be laying in the weather and the gravel driveway to do it - but if it acts up again, I may not have the luxury to wait

If problem resurfaces, I will see about bypassing the PCM or replacing the Crank Position Sensor (or both).

that_guy

Mine does the same thing untill it gets warm. I can watch the guage in the dash go from 10v up to 18 and back. The colder it is the faster it bounces. I can watch the headlights diim and birghten too. Sound like what your's is doing?

mini14

if its doing it when its cold, then stops after driving, its just your grid heater cycling

vcoyle

I'm having the same problem w/ the truck in my signature. This supposedly blew my battery yesterday. I moved the truck from my dealership after I found out what they were going to charge me to replace the alternator. Now the alternator is charging from 6 to 15 volts. The new shop is waiting to get a wiring diagram on Monday. Not having a backup vehicle is horrible. Any suggestions on what could possibly be the problem would be great.