Electrical Gremlins

[bobk]

Our cruise north is just three days underway and gremlins have arrived that must have been hiding during the southbound stint. I'll post them in separate threads.

For this one, we have a rebuilt alternator on the stb 6V92TA powering the starting and gen 8-D batteries. There is also a battery combiner leading to the house bank. Twice in the previous three days the volt meter dropped to 10 volts and stayed there even with the the generator/battery charger running. Then after a time, several hours or several minutes it came back up to 14 volts. Ideas? Is the voltage regulator integral or remote and could it possibly cause a drop to 10 volts. The voltage reading is the same at the upper and lower helms. Battery wires are tight as are those off the alternator that I could feel. No signs of melted insulation etc.

Bob

 

[Will]

I've had two alternators that wouldn't charge when the engines were started. After revving the engines up to at least 1800 RPM they'd start charging and acting normal, even charging at idle. I suspect it's issues with the internal regulators. Perhaps you should take yours into the shop to be checked out.
Will

 

[egaito]

I've had two alternators that wouldn't charge when the engines were started. After revving the engines up to at least 1800 RPM they'd start charging and acting normal, even charging at idle. I suspect it's issues with the internal regulators. Perhaps you should take yours into the shop to be checked out.
Will

My Cummins do this as well. If I leave the slip at idle, and cruise around that way, they never "kick in" and start charging. If I bring it up to 12-1500 RPM for a bit, they kick in, and stay in.

 

[Traveler 45C]

Same with my 871’s. Alt output will increase at about 900rpm.

 

[TedZ]

Assume both diesels are running. The battery charger has nothing to do with engine speed obviously and should have been charging/maintaining.

First item on the agenda is to put a meter on the battery in question to verify that the gauge is reading correctly. You are going to chase a lot of issues if the gauge is wrong and you are actually ok in the voltage department.

If you have an alternator where the engine has to be rev'ed to 1500 before it charges then the regulator has a bad SSR if it is a solid state regulator or a bad relay if not. They pick up but you have to coax them...not good as they will become uncoaxable! Alternators charge at 800 rpm or less. That is why they were so welcome in the 50's as the generators did not.

Ted

 

[bobk]

Thanks Ted. This will be a pain to check while underway, but I will get into it next time it happens. This is on the starboard side.

My port side does require a push to get it to start to charge. Usually rev to 1000 rpm does it. What's on a 1980 6V92, solid state or not??

Bob

 

[TedZ]

I would bet they are relay regulators. They can be cleaned and oiled lightly in the solenoid area but when they start to stick it is best replace it. Marine environ hard on relays/solenoids.

Ted

 

[Brian Degulis]

Many simple "ONE WIRE" Delco type alternators will not kick in untill the RPM is brought up then they operate normally. There isn't anything wrong with them other than they should have been set up to cut in at low RPM for diesel aplication but it's often not done.

If you have a field tap you can wire that into a pressure switch or to the key switch to engerize the field then it will cut in at idle. You can also take it to a shop and they can modify it for low RPM cut in. Or simply rev the engine to kick it in.

Brian

 

[Genesis]

Are these the flange-style alternators (no belt, mounted off the back of the blower drive)?

If so the regulator is internal and they are notorious for this; get it fixed as it will eventually stop working all together.

BTW, those alternators are made by Leece-Neville and are readily rebuildable. DO NOT attempt to buy a new (or "reliabuilt") one or you will be leaving parts of your anatomy at the counter in payment - take it to a good alternator shop and they'll fix it right up.

 

[bobk]

Karl they are indeed flange mounted and the bill for the rebuild in June '06 says Leece Neville. The rebuild was 3-4 hundred off the top of my head. should the regulator have been done as well at that price? What is a typical waranty?

Bob

 

[bobk]

Karl, thinking some more about this, how can a bad regulator drop the voltage instantly to 10 volts and again instantly jump back to 14 volts. The battery can't go down or back up that fast, can it?

Bob

 

[Genesis]

Not unless the battery is no good.

You may have a bad battery and the alternator is dropping out due to overheating; its charging, the regulator overheats due to what amounts to a shorted cell, and drops out - then re-engages when it cools down. Get out the ball float and check the cells and connections.

 

[bobk]

Re: Electrical Gremlins revisited

Well darn, now we have another identified gremlin and it seems related to the battery voltage. The synchronizer has been acting up and the slave engine throttle doesn't always disengage when the syncronizer is turned on. Today, I noticed the slave engine (stb) is showing 10-11 volts when the Glendinning is on, and normal 14 volts when it is off. It is a consistant thing now. So it looks like the charging system is OK, but how can the Glendining cause the voltage meter to show low voltage. The battery bank seems OK reading 13.5-14 volts with hand helt volt meter even when the ships instruments show less.

Bob.

 

[Pascal]

always always always verify voltage with a meter, dont' trust the gauge !

i'd look at the wiring diagram to see how the glen. is fed. i forgot off hand if there is a relay but if the switch is somehow on the same circuit as the voltmeter and you have a loose /corroded wire, the draw from teh synch coudl pull voltage down on the gauge but not in the rest of the system, coudn't it?

worth checking before pulling the sync out.

I have one wire alternators, they need to be rev up before they kick in 1200rom or so. Even modern alternators dont' put out a lot at idle or low rpm. look at the voltmeter in a modern car with AC and lights on it will dip even at 800 or 900 rpm.

 

[Genesis]

You got some sort of loose/corroded connection.

The Glendinning is VERY simple - get their troubleshooting manual - there's really only one or two things that can go wrong with it, the most common being that the solenoid is sticking (lube fixes that) or is not getting power.