Outlet on alternator of Perkins 4.236

The tach for the port engine (Perkins 4.236) has quit working, and in checking the tach connection at the outlet of the alternator I notice that the bolt on the alternator that the wire connect to seems to be loose. That is, it will turn. The nuts holding the ring terminals of the wire going to the alternator are tight, but when I turn the nut the whole thread assembly (that is, the bolt, if indeed it is a bolt) turns. I kind of assume that it is a bolt, and if it is turning then it is not making good contact inside the alternator. Am I correct that it is a bolt? If not, what does it connect with inside the alternator? Perhaps it is a double-ended bolt with no head, that screws into something inside the alternator?

Thanks for any suggestions. I may not be asking this question properly, but did the best I could.

John

What brand of alternator? It does sound like a loose wire/bolt. But to eliminate the tach as the problem, connect it to the other engine where you know you're getting a signal. If tach OK, disconnect alternator wires and see if by turning bolt you can tighten it in the frame. Clean connectors and spray with electric cleaner.

Look the alternator up on the mfrs website for a internal picture of bolt or just call the supplier as to how internally affixed if all else fails.

Um, I didn't quite give the whole story. There are two port tachs (helm and bridge) connected to the alternator, and neither of them work. Both were working. So most likely not a tach problem.

I do not know the brand of the alternator. It came with the engine, which came with the boat, which I just bought. What I can do, I suppose, is check the bolt on the starboard engine alternator (lot harder to get to, since it is next to the fuel tank, but I may be able to wiggle in there) and see if it turns too. If it is solid, then that points to a problem with the bolt on the port engine. I plan to go down there tomorrow (beautiful weather -- thank You Jesus!) and will see if there is a brand name on the alternator. Also may run by a place which rebuilds alternators and see if they might know.

Greetings,
Mr. jwnall. I think it's quite safe to assume that there shouldn't be ANY loose connections on your alternator or elsewhere in your electrical system.
From your initial analysis of both port tachs being DOA I think you are correct to suspect the alternator.
Since it sounds like you have SOME access to the port alternator. Why not take it off? Will give you some practice and you can have a much better look at just what you've got. Should only be two bolts and some wiring. GREAT excuse to check the other connections, clean up any gunge, check and adjust (on re-assembly) your V-belt and free up your mounting brackets (if necessary). Could also be a good excuse for an expedition to your local tool and equipment livery.
Disconnect battery(s) so you have NO, absolutely NO 12V power to any of the electrical leads on the alternator. Use your VOM (Volt Ohm Meter or Multimeter). No VOM? See reference to "expedition" above. There's a Harbor Freight in Tallahassee in the Parkway Center mall , as I recall and they're dying to sell you one for $4.99 (Item #98025...OK, I'm bored, I looked it up)
Depending on your skill level, tool selection, accessibility and patience it shouldn't take any longer than an hour and I wouldn't be surprised if you got it off in 15 minutes. Wear eye protection and keep the swear jar handy if you are so inclined. You shouldn't have to put in more than $0.35. Label ALL wires and make a diagram or take pictures of your wiring connections before you start. Assembly is reverse of above.
The local auto shop (Murphy's, AutoZone, NAPA etc.) should be able to check it out for you and I think some places offer this service for free.
Oh, if you DO go to HF, you can pick yourself up a reward/tranquilizer at the ABC store on Apalachee. (#3025-Right beside the CVS pharmacy).....Hmmm....Band aids?

Good advice, RTF.

I'd take it off and take it to an alternator repair shop to have it repaired. Loose connectors on any electrical accessory is bad. You might even find by removing the alternator, the solution becomes apparent.

The alternator tach contact should not freely rotate.... its contact internally has broken.... And alternator shop should be able to fix it....

Does the alternator still put out power to the batteries? If not then there is a possibility that something overloaded....but the alternator connection is a relatively low voltage connection.

The alternator does still put out power to the batteries. I think that the suggestion that an internal contact for the tach contact is either broken or flaky is most likely correct. I am going to take a scope down and put it on the AC contact and see if I have a pulse coming out of it. Should be about a 6-volt pulse as I understand it. A multimeter might pick it up, but a scope is better I think. If not, then will have to pull the alternator I guess. Which, as RTF points out, should not really be a big deal.

Thanks.

John

jwnall said:

The alternator does still put out power to the batteries. I think that the suggestion that an internal contact for the tach contact is either broken or flaky is most likely correct. I am going to take a scope down and put it on the AC contact and see if I have a pulse coming out of it. Should be about a 6-volt pulse as I understand it. A multimeter might pick it up, but a scope is better I think. If not, then will have to pull the alternator I guess. Which, as RTF points out, should not really be a big deal.

Thanks.

John

Click to expand...

John,

In the range of 6VDC is good...but if its 8VDC or slightly higher or lower than 6....don't be surprised.... You have an advantage being up where you are...ARCO is in Pensicola....and they have a really great tech guy....
He can be very helpful.....

What is ARCO??

Scratch the (dumb) question about ARCO. I did what I should have done in the first place and looked it up. Marine alternators, etc.

John

jwnall said:

Scratch the (dumb) question about ARCO. I did what I should have done in the first place and looked it up. Marine alternators, etc.

John

Click to expand...

Sorry....I should have said who they were....