Been most-days driving the truck The past couple weeks and noticed my alternator belt tension started going south and needing frequent adjustment. Shrugged it off to “ehh it’s old and getting broken back in”, adjusted and moved on with my day. Noticed yesterday while replacing a leaking steering hose, and trans cooler lines that were on their last leg the alternator bearing made much more noise then had when previously parked. And belts slipped on cold start. So leak checked what I needed to check. Started looking at alternator stuff and realized when full tightened was sitting cocked.

86 D150 100 amp alt, with AC and AUX Air Pump.

my thoughts are this.
a. 6 years parked was enough to warp the harmonic balancer, so maybe it was enough to fatigue the memory of the steel and I need to bend it back.
b. The alternator being new, could have the bushing/sleeve for the bolt be misaligned/bad out-of-box. (I did buy the cheapest one on the shelf )
c. I could have simply kept too much tension on the belts and now that the belts are shot, me having to have it close to the end of its adjustment range under tension is simply the culprit for the misalignment. Say due to length between pivot points.

if anyone else has experienced a similar situation, or even has a spit-ball idea to check or try I’m in to try it out. Truck is down for four more days anyway while I’m cleaning and inspecting other stuff.

 

Is it the pulley that's cocked, or the outer ring on the balancer? If it's the latter, need to replace the balancer, the rubber between inner out outer rings has degraded to the point it isn't doing its job any more.

 

The harmonic balancer was replaced when I first got it running. It would have worn out the belts in a matter of hours.

it’s not the pulley, it’s the whole alternator. Hang on, I’ll go to the garage to add a picture.


Hard to tell, but the belts are pulled more towards the front face of the pulley.

This is current tension (yes I’m putting on new belts, which is part of why I’m sorting this out) the circled bolt print is where these belts started about 2800 miles ago.

Where the upper bolt passes through: when tightened the alternator tweaks the unused hole towards the front of the truck.

since belts are $40 a pair I’d like to hear some input before I naw through the next pair. Also if anyone knows any ideas, toss’em my way.

 

Is the top hole in the alternator drilled at an angle?? (incorrect manufacturing)

 

The bracket is bent or cracked, It should be parallel to the one behind it. You need to see what's going on with it.

 

HeyYou - it was a reman, so I suspect all that happened was replacing that bushing that’s in there. maybe it was inferior quality or pressed in crooked?

Moparite - Any speculations as to what my have been the culprit? Figured it may be a known “gremlin” for trucks that sat undriven for as much time as this one has. (I’ve driven it more in a month, then it’s yearly average, and I’ve seen plenty of signs of “ehh it’ll be fine I don’t drive it much” maintenance /lack of)

I guess I could take some measurements to see how much I need to bend it, and could use some heat with a cheater bar/pipe over the end 🤔

 

The area in yellow is the area where I feel the warp occurred and can be corrected the easiest. Green is the direction of applied force.

With the angle of the bends existent in the bracket, I suspect if I bend back/down that should bring it back in line.


Figured I’d give it a go myself, and if I need to toss new belts on and soft-drive it to bigger hotter tools I can.

thanks gents.

 

check the area of the bottom thru bolt... and no, harmonic balancers don't "warp" I doubt the alternator itself is the cause, they reused an existing housing, they dont redrill anything.
a crooked bearing within the housing would cause a bind when the alt spins and possibly crack the case, unlikely. It's 99% within the brackets.... and I wouldnt worry about the belt being tensioned in a different spot within the slot, they arent the same belts that were on there to begin with, though if something in the brackets was bent and/or cracked that would help explain having to keep adjusting that often though it isnt uncommon to have to readjust some as belts stretch and wear in. Concentrate on the brackets/ what holes were used to mount (and if it were mine it would no longer have an air pump, story for later)

 

Is that long mounting bolt tight? When you had the alternator off was the bracket still bent like that? When you tighten the belts does the bracket bend? I have seen some bracket's get stressed and not hold the alternator in place without bending. Also seen stress cracks.

 

Sorry for the late response. I suppose my speculation on the failure cause of the harmonic balancer Could be wrong, as well as warp being poor word choice. None the less it was crooked and warbling when truck was acquired, and once change smooth as a top. So I figured tension fatigue on the bracket was plausible. I finally had time to work on the truck this afternoon and found two factors actually. The bracket was slightly tweaked, And a contributing factor which I straightened back out. But while reinstalling the alternator I noticed that the bolt pass-through for the bottom bolt of the alternator was actually too large and was more the cause of the misalignment then the bracket because regular fleas of bolt tension flops around like a fish. Calling my parts guy in the morning to inquire about it and get it exchanged. Will post again when I reach the next conclusion.

Lower bolt was tight, bracket was in pictured angle with alternator removed. When I tighten the belt to what felt like appropriate tension the bracket does flex slightly at the “S” bend but marginally, by which I mean isn’t enough tension to misalign the belts. Upon further inspection the lower bolt sleeve inner diameter seems to be the most prevalent and severe of the probable causes. When I cleaned all the welds off and inspected with a mirror under tension and found no stress fracking or fractures to the naked eye. Like stated above, I plan to talk to my parts guy tomorrow and I’ll give y’all an update once I’ve gotten some more information.


Thanks again for all the help everyone. It’s really appreciated considering how convoluted finding some of these specifications are on such an old vehicle.