problems with alternator

[rdbishop]

I have a 1968 MC7 bus with an 8v92 engine and automatic transmission.  My alternator has frozen up on me several times.  I have had it to three different alternator shops and had the bearings replace 3 times.  After driving for approximately 6 hours it freezes up.  When I let it cool down, it will work fine but when it heats up again, it freezes up again.  Has anyone had this problem?  And if so, what was your solution.

[pvcces]

You'll need to post the details of what you've got, so that people can help you.

For what it's worth.

Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska

[NCbob]

The first question which comes to my mind is:  Is the alternator being overspeeded?  With all the alternators out there working every day without similar problems this was my first thought.  The second question is:  Does the alternator have the right fan for the rotation it is asked to turn?  Alternators will work in eitherdirection (or so I'm told) but proper cooling would be a concern given the history of this particular unit.

I'm sorry I can't give an answer and it would seem that asking more questions wouldn't help solve the problem....or would it?

NCbob

[bruceknee]

If it is an oil cooled unit, is there a blockage to it?

[FloridaCliff]

RD,

Just trying to understand!

You are saying that the alternator seizes up and wont spin after lets say 6 hours.

By seizes up I mean doesn't turn.

Or do you mean doesn't produce any power?

And then you let it cool down and it spins and produces power?

I am just a little confused

Give us the all the details and we will be glad to help you......

Cliff

[rdbishop]

Sorry for the lack of information.  I am his wife and didn't know what information I should put in.  He is now telling me exactly what to say.  ---- 
It is a 225 amp., air cooled alternator.  It came with the bus before the 8v92 was installed.  It freezes up (will not turn), and breaks all 4 belts before he knows alternator is not functioning properly.  After it cools down, he installs new belts and then it works, until it heats up and breaks the belts again.  He installs belts from MCI, made for the alternator and all the same size.  He has replaced the belts several times because this usually happens when we are on a long trip.   We continue our trip by turning on the generator or using the invertor for power.

[roadrunnertex]

I think you need to call Mike Martin at Kirks Automotive 1-800-321-5989 EX102.Monday through Friday
Mike has helpd many of us bus fans out with alternator problems like you speak of.
I can not recall what Mike said that causes you problem with you alternator to lock up and burn the belts off.
jlv

[Greg Roberts]

Did this problem first appear right after rebuilding the alternator or did it first appear after many hours of successful operation? I have seen bearings of the wrong clearance installed and tighten up too tight from thermal expansion. Also, the must be a specified amount of thrust clearance in the assembly so that the bearings are not "pinched".

[rdbishop]

Thanks Greg for your response.   The alternator worked fine for years and it began to give me problems and has been giving me the same problems ever since (3 or 4 years).  I get everything running well and think the problem is fixed and then will take a trip in a month or so and have the problem again.  It was rebuilt 3 times by different alternator shops, which was recommended by Kerrville Bus Company in San Antonio, Texas.   Everyone I talk to seems to think the lock up is caused by the bearings so that is why I have them replaced.  But that doesn't fix the problem.

[Torquester]

If the belt tension and alignment is correct I'd suspect a problem with the alternator core. This could be a housing alignment problem. I'd opt for a completely different unit, new or reman. hth

Tq

[Sammy]

Does it burn up the belts at low engine rpm or higher engine rpm?

[rdbishop]

The belts burn up after I have been on the highway for several hours, high rpms, usually driving 65 to 70 mph.

[scanzel]

Are the belts being over tightened to the point of no play in them. I can remember years ago guys over tightening the belts to the point where there was no flex in the belts causing extreme side stress on the generator shaft which causes side stress on the bearings causing heat to the point of failure. I'm sure you have checked this but sometimes we over look the obvious.

[TomC]

Highly recommend you start fresh with a brand new alternator (not rebuilt).  Then you'll have factory warranty.  Look how much money you've spent, not even counting the aggrevation and time loss, by trying to salvage the same alternator.  There are many new designs of alternators out now to compete with the high temperatures that are being created by the new breed of trucks that have the smog engines (lots of heat under the hood).  Leece-Neville, Delco, all make updated new versions.  Use one of those new ones, and go down the road.  Good Luck, TomC.  PS-if you want expensive, I just paid $1,100.00 to have an exchange/rebuilt DN50 Delco 300amp with new regulator!