Alternator/Generator getting toasty with engine off

[RyanN]

To avoid confusion between a Diesel Generator for providing 120VAC and the Generator on our Detroit Diesels, I named this thread kind of funny.

So, we have not run the boat since Sunday, so no reason for the generator to be warm like it is.

I compared both generators for our DDs... the port side is warm while the starboard side is cold to the touch. I checked to make sure the keys were off and they were.

I've always noticed that the battery charger is running too, so somehow it's getting back current.

If your curious as to why I noticed this... I was rewiring our stereo on the boat today, dropped the tube of zip ties all over the engine. I stuck my hand down and noticed it was warm.

I would say it's about 115 degrees or so... not too hot to burn, but definitely hot enough to say "geez that's hot!"

Any ideas? I assume that there is a diode or something to control the flow of electricity, so that may be bad.

Thanks in advance!

[OBXTucker]

Do you have a battery isolation switch from the battery to the generator?
They're pretty standard on engines, but few people put them on generators. They weren't on Kismet's two generators when I took ownership, but I quickly added them to be able to disconnect power if ever necessary.

You're correct in assuming that it's getting current from the battery - and the charger that's feeding the battery. Unless someone has been running it in your absence!

Sorry, I can't help past the power feed portion, but I'd be concerned. Disconnect the battery until you can diagnose it further (imho).

Disconnect is just to the left of the generator.

[Canuck Dennis]

Check the fuel pressure switch, it may be in the closed position and the "alternator/generator is trying to turn,,,,probably shot by now....been there done that, rewired to eliminate the fuel pressure sw problem, even if it stuck closed..

[J's Dream]

I had the same problem...my stbd alternator was hot to the touch when the engine was off. My solution was to replace the ignition switch. Fixed the problem immediately. Less than $20.

[BUSTER]

I have not seen generators on engines since the early 60's,but if indeed it is a generator,the regulator has malfunctioned and it is trying to motorize much as a golf cart or lawn tractor does to start,then charge.

That being said,if you have an alternator and not a generator,the problem is much the same except the alternator is excited instead of motorized. If it is a one,or two wire /internally regulated "most are" alternator,with just a positive and negative cable,it needs to have a new regulator installed as this type of alternator is motion/RPM excited and the regulator is most likely stuck.If the alternator has an externally stimulated regulator check your ignition switch.If it is not the problem you are back to the regulator and the regulator will need to be changed.

Before you attempt to remove the alternator or generator, turn the battery switch for that engine in the off position and remove the positive cable "the large cable with a 7/16" or 1/2" nut on it" and tape the cable end up with electrical tape,then remove and label any other cables. Now put the battery switch in the on position.This will stop the battery draw and allow you to safely remove the alternator or generator for service.

[REBrueckner]

For an '80's boat, almost certainly you have an engine mounted alternator.

Buster posted:

" If the alternator has an externally stimulated regulator check your ignition switch. If it is not the problem you are back to the regulator and the regulator will need to be changed."

One clarification...last sentence:

An external "smart charger regulator" may be fed dc voltage via either the fuel pressure switch OR the ignition switch. I happened to have had one engine wired each way.

If you have an external "smart regulator" check the wiring diagram to determine which wire is the dc voltage supply...and almost certainly you'll find unwanted dc voltage there with the engine and ignition switch OFF....tracing that wire can be annoying because it's often wrapped in a bundle with other wires....see if you can find the same color at the fuel pressure switch if you can find that....remove the lead, and check continuity back to the regulator to confirm it's the same wire....either that, or somebody wired it to the wrong terminal of the fuel pressure switch....

[RyanN]

For an '80's boat, almost certainly you have an engine mounted alternator.

Buster posted:

" If the alternator has an externally stimulated regulator check your ignition switch. If it is not the problem you are back to the regulator and the regulator will need to be changed."

One clarification...last sentence:

An external "smart charger regulator" may be fed dc voltage via either the fuel pressure switch OR the ignition switch. I happened to have had one engine wired each way.

If you have an external "smart regulator" check the wiring diagram to determine which wire is the dc voltage supply...and almost certainl you'll find unwanted dc voltage there with the engine and ignition switch OFF....tracing that wire can be annoying because it's often wrapped in a bundle with other wires....see if you can find the same color at the fuel pressure switch if you can find that....remove the lead, and check continuity back to the regulator to confirm it's the same wire....either that, or somebody wired it to the wrong terminal of the fuel pressure switch....

Well then, it's probably an alternator then. I know it has a reset button on it, so I would assume that the reset button is on the regulator part. I'm going to have a looksie tomorrow after work. I'm hoping that it isn't wired wrong, but I'm not impressed with the previous owner's electrical job. I think the engines were rebuilt right before we purchased the boat, so it's possible that it was never wired correctly. What does the fuel pressure switch look like?

I know the throttles are cable driven, and the shut off solenoid just pulls a lever that kills the engines.

Thanks for all the input thus far.

[Canuck Dennis]

I would strongly suggest purchasing the engine manuals, you don;t want to be a good member of any towing company.!!!

[RyanN]

Hmm. Both seemed to be wired the same. I don't see how it ever worked. Don't they need the IGN connected at least?

I have a picture on my phone... I'll try to remember to upload it tonight when I get home.