srv8800

my truck wasn't charging so i replaced the alternator. it worked great for a day but now it's trying to throw 16v at the battery and it's boiling over. ideas? i gotta get to work in the mornin.. thanks

dkenny

bad ground?
the alternator is controlled by the ECM unless an external voltage regulator has been added..
depending on how far you have to drive..unplug the alternator.. you be running on battery only..so turn off everything you can.

-dkenny

srv8800

already did. ground looks solid. any other ideas? thanks

Robert Rausch

I'd say the internal regulator failed. I'd take the alternator back to where ever you got it and ask them to test it. Most places that sell alternators also have the equipment to test them.

I've replaced internal regulators before--it's not a big deal.

nickg

to my knowledge the voltage reg is in the ECM/PCM not the alternator, so that would mean the alternator is fine, the ECM is not.

you can get an old dodge external regulator or 15-20$ or so and wire it up rather than replace the ECM/PCM, that will eliminate the overcharging, and is cheap and easy to do

Robert Rausch

Nick, I think you're right. The internal regulator I replaced was on a GM alternator that is on my old tractor.

blackimpala

If you want to try the external reg here's the way it's wired up.
http://www.cumminsforum.com/forum/94...w-89-02-a.html

I did it on my truck just to trouble shoot it.

Floyd

Busboy

Could be the ground cables internally. Just short to ground from the Neg battery post and see if it cures the problem.

infidel

Anymore the first place I look when there is a problem is at any new parts.
The quality control is very poor.
Have the alternator tested, if it's good do the external regulator mod.
The regulator failing in the PCM but everything else working normally is somewhat common.

mechmagcn

Yep, used to have a Dodge van that would boil the battery when running and then drain it when not. An external regulator took care of the problem.

bent valves

You don't say which battery is boiling or if it is both of them but if it is only the passenger side, try cleaning the battery terminals on the driver's side. As strange as this may sound, the PCM samples the voltage on the driver's side and if the connections are dirty it will boil the passenger's side battery.

srv8800

the truck only has 1 battery, the driver side. the alternator is brand new. i replaced that thinking it was the problem before it started boiling batteries. doesn't sound like anything is wrong with it, right? sounds like the voltage regulator just died. should i replace the computer or add an external regulator? a used computer off ebay can't be that much..

blackimpala

Check out the difference in prices, In my opinion the external reg. is a good fix. Has worked on many cars for many years.

infidel

Don't know about you but $20 vs. $600 is a no brainer for me.
Plus you might have to pay the dealer to reprogram a new computer which will probably cost at least fours time more than an external regulator.