Alternator Troubleshooting - Case Study

[Maine Sail]

Hi All,

I thought this would be a fun exercise. In the world of Biotech where I used to work case studies were a fun mental exercise.

I will present the data as it was presented to me and then you guys get to throw out ideas of what the issue may be or was.


Case:

An owner of a 34 foot sailboat had installed a new Balmar 60 series 100 amp alternator and ARS-5 regulator. He told me he was "not happy" with the performance but was not overly descriptive.

The boat has two analog volt meters, one at the engine panel and one for the two banks of batteries with a toggle switch to select which bank you're looking at. There is not battery monitor or ammeter of any kind.

With the batteries at rest the volt meters read nearly 15V. With the engien on they read the same. There is no solar on the boat.

The engine panel meter reads 14.5V with the batts at rest and the same when engien is on.

The banks consists of 1 each Lifeline AGM group 31's via a 1/2/BOTH/OFF switch.

The alternator is fed through the factory wire harness to the starter post where it picks up the wire to the common post of the battery switch.. The factory wire to the starter is roughly 10GA and about 4 feet long before it meets up with the 1GA battery cable.

Battery wire is original 1981 and 1 GA.

Alternator was non-operational.

There were multiple problems, one of which was the alt was non-operational. What could they have been?

This is the access & visibility I had of the alternator.

 

[Witzend]

Right away it look like the belt tension adjustment is maxed out. loose belt = nominal or no output. I would also think that the analog meters are out of calibration. 10guage seems pretty light for a 100amp alt output.

 

[Velero49]

Was the regulator working? Could you read the short/long display in the regulator? if not check fuse to the regulator. Fuse OK - continuity test and voltage on hardness between alternator and regulator? hardness Ok - altenator and temp sensors disconnected and try again. Now the sensing wire (blue) do you get any voltage after you wait a few minutes with the engine on? if not regulator may not be working.

A couple of concerns - that old cable may have a huge resistance causing a voltage drop and that the 15 V reading is very high - check w/volt meter to confirm.

 

[Maine Sail]

Right away it look like the belt tension adjustment is maxed out. loose belt = nominal or no output. I would also think that the analog meters are out of calibration. 10guage seems pretty light for a 100amp alt output.

-1 Not belt tension

+1 Analog meters are WAY out of calibration as they often are

+1 10GA was part of it

 

[wetass]

Is that an isolated ground terminal on top of the alternator - and if so, I assume that "fat" red wire is the 10ga making the green ground connection (I assume that is what that is?) 14 or 16 guage at best - 100 amps might be a bit much for that if Im seeing that correctly.

 

[wetass]

ONe more thing occured to me - If that alternator isn't working at all (and I assume its grounded with a 14ga - probably through the engine panel somehow) then the batteries are likely almost dead - Id be surprised if they both were the same voltage unless somehow they are being parralled - How did he wire his toggle switch?

 

[Maine Sail]

Is that an isolated ground terminal on top of the alternator - and if so, I assume that "fat" red wire is the 10ga making the green ground connection (I assume that is what that is?) 14 or 16 guage at best - 100 amps might be a bit much for that if Im seeing that correctly.

+1 Bingo!

The tough thing when called in to trouble shoot someone else's work is always understanding what they've done. The owner told me he "grounded" it and on some alts you can ground at a couple of places the complete back of the alt was nearly impossible to see even with a mirror. I initially trusted his statement and began the trouble shooting steps.

When going through all the steps I discovered that with the key on but engine off I could see 8 volts on the field. When the motor started it dropped right off to about 1.2V. There was enough of a ground to get the reg to turn on but not enough to support it when the alt was trying to develop output. Problem = bad ground or bad termination.

The major issue is that Balmar alts are not case grounded and there was no ground but the owner had cleaned the mounts well thinking it was grounded to the engine block. There was no ground wire large enough to handle the alt when powered up enough to even get the field voltage above 1.2v which is not enough to kick it into output mode.


Solution- The fix was to add two 4GA wires, one negative ground direct to the batteries and one positive wire direct to the starter post. I will be installing a combining relay and battery monitor within the next few weeks and the alt + will go direct to the house battery bank for the most accurate sensing.

Another issue discovered was a 0.4V drop between the alt and the batteries because the regulator sense wire & regulator negative / black wires were on the alt output posts and the battery cable terminations were in rough shape. Once the alt output can be run to the bank the positive & negative sense will be moved to the battery post so the alt can see the correct battery voltage and adjust its output accordingly..

Voltage Sensing is a critical part of alternator regulator installations!

Regulator RED/V-Sense AND regulator Black/Neg MUST be wired to the same bank the alt is feeding if you want the performance you paid for. The reg black and v-sense wire make the voltage sense circuit. Simply addressing the red is only HALF your voltage drop!!


Leave it to a CS owner ti figure it out!!!

 

[Witzend]

Nice find! Yea, there are always multiple problems especially if someone was working on it before. Hmm, no case ground on a Balmar, I will put that in my Funk and Wagnalls.
If I'm interpreting the picture you supplied correctly, I would still be concerned that the adjustment range for the belt tension is maxed out.

 

[kloudie1]

Excellent, Maine.. That is one of those things that will be in my head every time I work electrics now..