No power from alternator 99 24V
 

So i just put a new reman alternator in my truck and im not getting any power from it. Everything is installed correctly and the alternator/batteries are good, but the truck only starts intermittently. As far as i know everything is wired correctly, never had an issue until the past week. I have nothing on the voltmeter and when the truck is running, its only running off the battery.

When i go to crank it, it does nothing, like theres a lack of power.
Any ideas?

First thing to do is check your batteries. DO NOT GUESS! They have to be good. Clean the battery terminals and all the grounds you can get to. This is as important as good batteries. After the 1st 2 have been done, check for voltage across the alternator brushes and see if you're getting power from the regulator. Check voltage at the alternator output and then at the batteries. Report back what you find.

Another thing to is you may have bad starter contacts. If you hear the starter solenoid close, and if your batteries are good, then your contacts are worn out.

Do not buy a new starter! The original starter (made by Denso) is a very well built piece, and is easily serviceable. The quality of a new starter from a parts store is nowhere near the original starter.

I had my starter contacts wear out about a year and a half ago. First time I got a no start, I pulled it apart and only cleaned the contact surfaces with my Dremel. That fix only lasted for a few month and then starting became intermittent. That's when I ordered a new set of contacts (comes with a solenoid plunger). Been good ever since.


Use this thread for reference, it was written by one of our memebers, BC847: https://www.dieseltruckresource.com/...tarter-141395/

Both batteries and the alternator tested good, the starter was replaced in december. The truck starts and runs just fine, but its gotta be running off the battery since it dies if i disconnect one.

If it is doing that, then I would suspect that your battery cables are corroded on the inside. Inspect them very carefully and look for cracks, bulges, and/or corrosion.

It could also be the 140A fuse from the alternator to the PDC on the driver side fender.
Espexially if you had an arc when working on the alternator or while changing the oil filter.

^^^^ More than one of us have taken that fuse out on accident........ [redface]

Does it matter which one?

My PCM stopped regulating voltage a few years ago. All other functions are fine.

Did a 1st gen external regulator setup and has been fine (besides cheap aftermarket VR's not lasting) since.

Do look over the simple things first. I know the battery temp sensor is part of the charge control circuit too...something else to consider.

Checked and replaced the 140amp alternator fuse. Battery voltage went back to normal and the truck started right away. Let it run for a few minutes then shut it off and went to start it again. Same thing, voltage at the low end and wouldn't crank.

Ok, now charge your batteries overnight and try it again.

Now take another look at that fuse. Sometimes the cable from the alternator to the PDC gets chafed, and sometimes (especially with aftermarket alternators) you have an higher output than the fuse can handle. So with empty batteries and the grid heaters you slowly melt away the fuse.