NHC250 alternator pulley loose, throwing belts!

[sed6]

NHC250 alternator pulley loose, not charging?!

I've lost count of the number of belts it's thrown in the last year, prolly 6-8. I finally identified the problem as a loose alternator pulley that wiggles and throws belts off. I tightened it down once only to have it come loose again. I was going to red locktite the nut tonight but the pulley seemed to bottom against the alt housing before the nut drew tight. What's going on here?

Add to that the pulley also rotates about 45° on the shaft instead of being more permanently fixed. Is there a keyway on the shaft and pulley?

I tried to get the pulley off but my puller bottomed out before it came free. It's dark and after hours now so I'll look for a new puller tomorrow.

I appreciate any ideas or suggestions!

 

[98G]

The A2 pulley has a keyway as best I can remember. And I'm thinking the alternators are interchangeable across all 93series, so I'd expect a keyway on the nh250,as well.

I'd start by pulling it, realigning it, and cranking it down. (Which is obviously what you're doing)

I never had to replace a belt on that truck the entire time I had it, fyi. (For that matter, I've never had to replace a belt on any of these trucks...)

 

[Shoprat 19th Engr]

Sounds like the pulley is worn on the backside and in the front of the pulley also sounds like the keyway on the pulley is worn bad you might take the pulley off and have a new keyway cut in the pulley and put a thick washer behind the locking nut and this should fix the problem

 

[sed6]

I'll have to pull it and look but I wonder what forces in play keep the pulley from being drawn down tight against the housing?

I think it chucked it's first belt right after I got it...

 

[73m819]

First he DOES NOT have a a2, the key sheared which allowed the pulley to walk, wearing on the shaft and the pulley mounting hole, THIS just made things WORSE, you CAN NOT straighten things, the alt/pulley NEEDS TO BE REPLACED.

 

[74M35A2]

98G didn't say OP had an A2, he gave his experience and said the OP's engine was likely the same. Stock mil alternators are garbage, and yes once broken loose it will damage and continue to do so. An $89 Chinese Delco would be a suitable replacement. You will also need a pulley which are easy to find for them. As a last shot, you could weld your current pulley on and call it a last effort since these things are junk to begin with and even worse once "rebuilt".

 

[sed6]

Think I'm better buying the alternator and pulley myself or going for this? http://www.wolverinetechnologiesllc.com/M925Alternator.html

I'm not sure where to find a pulley by itself.

 

[74M35A2]

I could point you to the pulley, but for the $89 alternator, the distributors don't even have a listed phone number, and don't really offer returns if failed, though they say they do. I'd go with the Wolverine one. He is a member here, he answers his published phone number, he will honor the warranty, and has already done the homework to include all of the fasteners and pulley and such you will need to make it a bolt on deal. That alone is worth the additional $100 or so he gets.

 

[swbradley1]

If you go with the civi version you already have the needed pulley. If it is just loose and wobbly you have to drill it out anyway to go on the Delco style.

Wolverine is good to.

 

[Spyderman]

Think I'm better buying the alternator and pulley myself or going for this? http://www.wolverinetechnologiesllc.com/M925Alternator.html

I'm not sure where to find a pulley by itself.

Sounds like the way to go.

 

[simp5782]

Oshkosh has the A1 pulley for about $80. or I have one for $20 shipped.

 

[74M35A2]

If the pulley spun on the shaft already, like it has several times, the shaft and pulley will not be true anymore to hold correctly again, even with a new key. Weld it on from the nut end with a big glob, or replace the entire thing. People are still paying good money for working mil alternators, you could cover at least half or more of your replacement cost. Just be honest in the assessment of it, which most people are. That's what I would do anyway. Another big bonus about a Delco or Delco clone is it won't over-volt on improper shut down and trash your ABS module.

 

[sed6]

Got it out and apart...

Got it out and apart. Indeed the key on the shaft ate the inside of the pulley. The key faired fine and just needed clean up with a file. Same for the inside of the pulley. With them both cleaned up they just slide right together relying on the nut to hold them together. My pulley doesn't bottom out after all.

So it might be repairable. Maybe a machine shop can cut a new keyway or I can always weld it on.

While I have your attention, what's the small wire here do? It's connected to just one terminal as shown by the pencil, but the others have signs of being wired up once as well.

 

[jonesal]

Your unit needs repair if you plan on returning it to service. You need a new rotor and pulley. I have attached two documents - a parts list and a wiring diagram. The "R" is not used on the 250. The parts show up fairly frequently on ePay. You have lost shaft section - if that lets loose, you could have some very expensive repairs.

Al Jones
M923

View attachment AMA Parts List.pdf View attachment AMA-5104UT_wiring.pdf

 

[sed6]

Thanks all. I was able to find a replacement pulley for cheap and will slap it on when it arrives.

 

[73m819]

THE SHAFT IS NOT REUSABLE It WILL break which could BUY a RADIATOR.

 

[Monkeyboyarmy]

Yeah. That pulley wont last long on that worn out shaft. I have new rotors.

 

[sed6]

Yeah. That pulley wont last long on that worn out shaft. I have new rotors.

You guys probably know better than I but why not? Is that little ground up area behind the key that bad? It doesn't go all the way around. Several washers on the front overcame the stripped threads and gave the nut good threads to grab on to.

I just don't want to throw too much money at an old one if a new clone can be had for $100-150.

 

[sed6]

Let me ask, how hard is that rotor to replace? I appreciate the exploded diagram above! It looks straight forward, are the bearings pressed on the rotor shaft? Will I need any special tools?
Thanks!

 

[73m819]

You guys probably know better than I but why not? Is that little ground up area behind the key that bad? It doesn't go all the way around. Several washers on the front overcame the stripped threads and gave the nut good threads to grab on to.

I just don't want to throw too much money at an old one if a new clone can be had for $100-150.

1 -- The shaft got HOT
2 -- The gouge is BEHIND the pulley, the shaft bends a bit there now the shaft can bend more and then BREAK.
3 -- The pulley will NEVER be true, this WILL cause vibration and the SHAFT WILL break.

This is your truck. your money, you asked for advice, you got it, You have TWO choices
1 -- Fix it right the FIRST time OR
2 -- Fix it right the SECOND time AFTER you FUBRED the radiator.