Balmar 7 series alternator locking up

[cwyckham]

Check what the field output is as well. Is the regulator full fielding? What is the voltage output? I had my MC614 putting out full field and putting 17V into the batteries. Regulator ground wire was broken. You may be concentrating on the alternator and not seeing the root cause of the original failure.

[GordMay]

Originally Posted by s/vbuckeye

... 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.

Belt failure at < 125 Hrs is very premature.

The most common reasons for premature belt failure are improper belt tension (too loose or too tight), poor alignment, pulley damage or distortion, environment (excessive heat and ozone), and using an improper belt for the application.

Belts that are too tight put an excessive load on pulleys, shafts, and bearings. Excessive belt tension will also wear out a belt quickly.

Pulley warpage, nicks, and normal wear take their toll on belts as quickly as poor alignment and improper tension. Pulleys should have a smooth wear pattern for 360 degrees and be free of any irregularities. Even a small nick or rise in the contact area will go through a belt in short order. A pulley with runout (warpage) has the same effect as improper alignment because it puts unacceptable side-loads on the belt.

Pulley misalignment, distortion, and misfit can go through a belt in a few hours.

When belts track normally through pulley sheaves, friction between the sheave and belt is reduced. Heat dissipates more quickly as the belt moves through pulleys when there's proper alignment. What's more, accessories such as alternators, water pumps, power-steering pumps, and air-conditioning compressors turn at normal operating speeds. When pulleys are misaligned, friction increases substantially, putting excessive side-loads on belts.

The best indicator of pulley alignment is a straight edge* along with temporary belt installation. The belt and straight edge should be parallel with the pulleys.

Belt width and pulley width must match, in every respect, for proper function. Width match is important because there should be full contact (traction) between the belt and pulley.


* See ➥ Belt & Pulley - Cruisers & Sailing Photo Gallery

Or ➥ Belt & Pulley - Cruisers & Sailing Photo Gallery

[sailinglegend]

Originally Posted by GordMay

............The most common reasons for premature belt failure are ............using an improper belt for the application.

You need a 5/8" belt for a 110 amp alternator. My 100 amp alternator still has a 1/2" belt but we decided that it was much cheaper to change it every year than get three new pulleys made for a bigger belt.

[40 South]

I run 2 x 95 series Balmar alternators, MC624 external regulators with 2 x 1/2" belts each. I change belts @ 1000hrs = yearly........because I can (preventative maintenance). I don't want failure!

125hrs is very short!

Check the long case holding bolts are tensioned equally to keep the two end cases, shaft and magnets in alignment. If they are not tensioned equally when the alternator warms up it can distort/twist and the internals bind!

[Cheechako]

Some of the stock alternators (and pulleys) run small belts... like 3/8 ish. Belts size is not relevant here though as the poster has run the system for years and it was fine.

[Dsanduril]

Belts size is not relevant here though as the poster has run the system for years and it was fine

Not sure I agree. OP has said belts used to last 125 hours, which is very short life for a belt, indicating they are undersized and that the system didn't actually function properly (even though it did keep the batteries charged).

Scenario, old alternator is dirty (maybe from belt dust?) and runs warm. ARS-5 senses alternator temperature and dials down output. New alternator installed. Nice and clean, runs cooler, ARS-5 dials up output. If running next to the ragged edge on belt capabilities (as witnessed by short belt life) additional load (even if only a few amps) could send things over the edge quickly. Belt starts to slip right away (appears as if alternator is locked-up while in operation).