My 91' CTD, before I got it, had a history of alternators going bad... the previous owner rigged an air scoop injection (piece of dryer vent hose) to gather air and cool the alternator while going down the road. I have put over 100,000 miles on this truck since I got it (scoop still in place) from him and have not had an issue with the alternator at all.
The 89' I just obtained (retired scool bus service truck, CTD, with utility bed, 192,000 miles) had a belt tensioner that was making noise. I went to Advance and got a new belt tensioner. I was familiar with the Dayco brand as I had put one on the '91 without any problems. When I went to put the tensioner on the '89, it would not fit. Scratching my head, I noticed that the new alternator (installed by the PO) on the '89 has a fan on it... I went right to the '91 and it has no fan.... I tried replacing just the pully
($23) but the rascal is still making noise... I have, by way of elimination, determined that it is, in fact, the belt tensioner that is making the noise..Do I grind the belt tensioner untill it clears the alternator fan (and mess up any warranty it might have) or remove the fan from the alternator?

 

Interesting,
Where is the fan behind the pulley, is like the fan on the HO Delco units.

I had to grind a relief in my tensioner also to clear my Leece Neville and I had no problem returning it for warranty, I used my die grinder and did it carefully and it just looks like part of the factory casting and after it got dirty all of the grind marks blended in.

I think the heat from the exhaust manifold and the turbo is what kills the alternators on these trucks, I was going to fabricate a heat shield to deflect the heat on mine.

Some of the high amperage units have a cold air duct in the housing.

In the 70's the alternator to use was off the old Dodge Highway Patrol cars, it was a 150-amp large frame Leece Neville that was shrouded and had a cold air duct that came from the core support.

Can you get some pictures of it?
Jim

 

I'll take pictures... the factory tensioner was just fine,,, the Dayco is just a little bulkier.. I'll get pictures this morning... I gotta take it off anyway.

 

The first picture compares the stock tensioner to the dayco... the second picture shows the clearance and the third picture shows the fan on the alternator... I ground down the boss on the dayco and it clears and is working...

 

Grind the tensioner as required.

 

For some reason that doesn’t look like the same NipponDenso alternator I had on my truck although there are many variants.

When you get it all back on the truck and have the belt on, take a good look and sight down along the belt and make sure the pulleys are lined up and the belt is running flat because I have a feeling it might not be because when they installed the fan behind the pulley, unless they machined the back side of the pulley down to match the thickness of the fan web it might be forwards about 1/8".

A clue could be the back edge of your belt is a bit frayed.

Or since you also have another truck see if you can get a measurement from the face of the alternator to anywhere on the pulley and then compare the two.

This could cause tracking problems for the serpentine belt and could cause premature wear the same as a bad idler could.

The fan is a good idea and I am not putting it down in any way but I just wanted to make sure it was straight; I have rebuilt many alternators and stuffed oversized units on lots of different engines and alignment was always critical.

Jim

 

Don't 89's have a different alternator than 90-93? I was thinking the one on the '89 looked different.

 

That is either a Chrysler 60/90 or a Bosch 90 amp alternator. Unless Chrysler used something special on those early trucks.

 

Everything appears very lined up and straight... I looked but could not find a manufacturer's name on the alternator.. I'll look again...

 

'89's did have a different alternator.