Balmar 7 series alternator locking up

[s/vbuckeye]

I have a Balmar 110amp 7 series alternator with a ARS-5 voltage regulator that has locked up, the pully won't spin. I just had it replaced and the new one locked up 10 minutes after I pulled away from the dock. Any ideas of what could be causing it to lock up? Some magnetic field issue?

Thanks,
Ben
www.svbuckeye.com

[David M]

Locking up so bad you can't physically turn it by hand or failing to work? The only thing that is going to physically lock up an alternator are bad bearings. No sort of electrical field is going to make it so that it cannot turn at all. The force from your belt is greater than the resistance from the magnets working against the magnetic flux, especially at slower speeds.

Is your belt tight enough?

[donradcliffe]

When you apply field current to an alternator, it gets hard to turn, but not hard enough that a well-tensioned belt can't turn it, even when it is putting out full rated amps. When you turn the motor off (and the field current is turned off), the alternator should be easily spun by hand.

Who did the replacing--you or a mechanic??

[Cheechako]

It's got to be something physical. A chunk of debris from something failed inside. or a REALLY bad bearing!

[bobconnie]

+1 on the bearings, either installed wrong, ot the wrong ones !! Did someone install them with a hammer and a hunk of pipe?? sorta sounds that way !! Just a thought

[s/vbuckeye]

update - it seems to be the magnetic field is building and locking it up. Mechanic did the install, professional rebuild shop rebuilt the alternator. There aren't any error codes showing on the ARS-5. Wondering if there could be something downstream in the electrical system that could be causing the problem. We have a fairly complex electrical system with multiple charge inputs: solar through an MPPT regulator, wind generator through its own regulator. Also, this is a catamaran so another alternator. The system had been stable and running properly for two years before this issue appeared.

[donradcliffe]

1. Try to turn the alternator by moving its fan with the belt on--it shouldn't turn.

2. Take the belt off and try again--it should turn easily.

[Sailmonkey]

Originally Posted by s/vbuckeye

update - it seems to be the magnetic field is building and locking it up.

I just don't believe this is possible unless your belt is way too loose.

Do you mean that when the engine is turned off (or the regulator is off) the alt turns freely?

[Dsanduril]

We're all curious, but I think we need some clarity on what you mean by "locking up". When the engine is off, can you take off the belt and spin the alternator pulley? In that case I would not consider it "locked-up", so there may be a language/usage difference between us.

If it is only "locked-up" while running, is the symptom that the belt starts to slip and makes a lot of noise?

I think we need to be clear whether it locks up and dies, never to run again until replaced, or if it locks up while running, but will then run again after being stopped for some period of time.

Also, is there an idler pulley? Could be nothing wrong with the alternator, and the idler bearings locking up with heat, this would explain the same symptoms with a new alternator if there is an idler.

[s/vbuckeye]

The newly installed rebuilt alternator siezed and broke a belt that only had 15 hours on it (and was tight) and the engine had only been running for about 10 minutes. However, once it was stopped, we were able to move it again so presumably mag flux, not bearings. Mechanic came back out, changed out a failing oil pressure sensor, changed the belt load setting setting on the ARS-5, obviously replaced the belt. Ran it under heavy load for 15 minutes and seems to be working. Calling it good for now since we can't seem to duplicate the problem again although I'm a bit skeptical. We'll see when the new belt gets a few more hours on it.

[Cheechako]

I wonder if debris was inside the alternator from the rebuild ("now where did that little screw go? Oh well I have another one here...")

[Sailmonkey]

Originally Posted by s/vbuckeye

The newly installed rebuilt alternator siezed and broke a belt that only had 15 hours on it (and was tight) and the engine had only been running for about 10 minutes.

Why did you remove the alternator in the first place? was the belt that failed used on the previous alternator that failed? How old was the belt (in years)

[s/vbuckeye]

original alternator locked up, suspect that it locked up magnetically which then caused it to burn up bearing that caused it to lock up mechanically but can't prove it. Rebuild alternator was then installed and still having mag issue which killed a 15-hr old belt, recently purchased. All belts have been fairly new since I have never gotten more than 125 hrs on a belt.

[DeepFrz]

What size is your belt?

[Sailmonkey]

We've got a 7 series also, they're hard on the small belts they use. The only thing you can do is turn down the max field current. I don't know if you can do this with a Balmar but I can with our regulator.
Before I did we were about 150-200 hrs on a belt