Newell Gurus

I put a brand new Delco Remy alternator in with new belts.   It only shows 12.3v on the Blue Fire.  Any ideas why this would be? Belts seem to be tight I torqued the pulley but to 80ftlbs that it stars on the alternator

Internal or external regulator?

Why did you replace the old one?

Internal voltage regulator. The old one was making noise had a broken rotor inside

And have you measured voltage at the alternator with a meter?
Were the batteries down on charge?
Just trying to get the total picture before condemning the alternator.

So I got a good meter. Batteries measure 12.89 V they measure 12.89 V at the main battery shut off switch where the cable goes to. I believe the alternator and the battery merge switch my eye terminal is receiving 12.8 V the ground checks good with an ohmmeter with the engine off I’m showing like .6 V at the alternator positive. if I turn the house batteries on it shows 11.3 V not sure why that would be related to chassis.. with the engine running I still show 12.89 V at the batteries and blue fire shows 12.4 V I cleaned every battery terminal. They’re spotless, clean the terminals at the chassis shut off switch, which did have some corrosion on them. They are now absolutely spotless I’m confused.

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These are pictures of my rear power box

Have you tested voltage at the alternator with engine running ? The reading of .6 DCV seems suspect , I believe that should be battery voltage . 
Chris

Also, check at the alternator itself at the output terminals. I had low battery voltage and it was actually loose alternator belts! The belts seemed tight, but actually it was the weight of the alternator pulling down on them, the tensioner was completely loose!

YMMV

Assuming the voltage checks out at 13.7 to 13.9 directly at the alternator terminal with the engine running………..

The voltage that the Bluefire is reporting is taken from the Detroit DDEC computer.

So the alternator voltage could be OK and the computer not getting the proper voltage. The first place to check voltage would be at the two circuit breakers in the right rear engine electrical compartment. There are the only two push in circuit breakers in that compartment, and they are labeled. https://newellgurus.com/showthread.php?tid=5756

I emailed Creslie at Newell yesterday morning he responded within 20 minutes via email and said he would have someone call me at 9:15. I had a tech call me exactly at 9:15 talked for a while. He went down and looked at a coach similar to mine. It was in for service. Give me a couple things to look at.. I ended up, jumping the alternator post from the isolator to the chassis batteries after taking the ground off the chassis, batteries and reconnecting after. And 12.8v at alternator Started the boss took a reading with a meter at the batteries. It’s now pushing 14.2 V into them. The isolator is bad! i’ve been thinking about this and trying to get my head wrapped around it for a couple weeks.. But I have learned a lot about how this coach is wired in the back with the chassis and such and I’ve definitely learned how to use a multimeter properly.

Good for you Willie! I do have a question have you been merging your batteries much?