Scorching hot alternator pulley

[Flanders 46]

My PA Performance alternator has stopped working again.  The pulley is getting super hot!  I measure the temp with my pyrometer about 30 seconds after the car is running, when I stop the engine.  The alternator case +engine is around 70F but the alternator pulley is 240F!  I've tried both PA Performance billet and my OEM pulley, with a new v-belt on fairly tight (barely 1/2" play).  I've also had the battery on a trickle charger overnight (a few days, actually) just in case it was dead, but didn't seem to make a difference.  I have not tried a new battery yet.  The belt doesn't feel very hot either.

Prior to testing, battery voltage reads solid 12.8V.  When the car is running, voltage drops to 12.3V.  When the engine is off again, voltage goes back up to 12.8.  The case of the alternator, along with the internal windiings, seem to stay nice and cool (according to pyrometer) so I don't think the alternator itself is overheating.  It seems to only be the pulley (and the nut keeping pulley attached to alternator)

 

When the engine starts up, there's belt squeal for a second or two before it's quiet (might even be power steering belt, as it's definitely a bit on the loose side). PA Performance is convinced the belt is slipping, causing the excessive heat.  Any thoughts from the years of wisdom here?  I'm at a loss.  The alternator is aligned pretty good, perhaps maybe a degree? off center, but I wouldn't think this would cause the pulley to overheat so quickly.  Not sure I can crank the v-belt much tighter.  Help!

[J's69Mach1 17]

Any noise coming from the alternator bearing ? Where pulley sits there should be a spacer also, I am Just saying ideas. 

[Mach1 Driver 560]

How many amps is the alternator?  From what I've read, anything up around 95A needs two v-belts or a serpentine to drive it. It certainly sounds like the belt is slipping. I know some people say they have no problem with a single v-belt, but others do.

This may be of little help, but shows the mental gyrations I've been going through to solve the belt problem on my car. Depending on your accessories, going to a serpentine will usually require getting rid of the stock fan and using electric cooling fans- which drag an additional 20A. That's counter productive in my opinion. I prefer the look of the stock fan and v-belts, and I've been looking at them for 50+ years, so I really don't want to switch to a serpentine. I have PS and AC so I'm already running 3 belts. One approach would be to extend the PS belt around the alternator and use two pulleys there. However that changes the contact area for the PS belt on the crank pulley, potentially causing a problem with PS operation.

What I'm investigating is using a double-v belt. This type of belt has a "v" on the top and bottom. It would allow me to make a custom bracket for an idler pulley (like the one on the AC) so a single double-v belt for the alternator will have more contact area on the single alternator pulley. My preliminary investigation shows the contact area on the alternator pulley is increased by 55%, and by 48% on the crank pulley. The available belt length factors into the design. because these belts usually tend to be longer than what is really needed here. The workup below is using a Mitsuboshi 1222  double-v belt which is 48.1" long.

I have to get more accurate measurements on the exact positions and dimensions of the components before I can proceed further, but it looks promising.alternaor pulley.pdf

[danno 128]

I am sure you have considered this, but are you sure the V of the pulley is the correct top width, bottom width, and angle?  Is the belt correct for the pulley?  

Going along with what Mach1 suggested, another option is to have the V belt wrap further around the alternator pulley.  This requires a flat surface pulley to push the back side of the belt in,  I have seen serpentines use these all the time. 

Also as suggested, maybe it is the bearing? 

It is also odd that the voltage drops from 12.8 to 12.3 when the car is running.  It is supposed to increase to 14.4.  That indicates it is being overloaded, and that will heat it up.  Disconnect all wires to the alternator and run it to see if it gets hot.  That will definately tell you if the heat is from the mechanical spinning or electrical load. Without lights and a fully charged battery, a car should run for an hour or more on just the battery. 

[Mach1 Driver 560]

5 hours ago, danno said:

This requires a flat surface pulley to push the back side of the belt in,  I have seen serpentines use these all the time. 

Yes we all have seen serpentine belts which are thin and wide, where the outside wraps around an idler pulley, but can you show us an example of a single V belt doing so? I would be interested the application. I don't recall seeing a pulley made for that purpose, whereas a double V belt is trapped in the V of the idler pulley, so it can't flop over and spin off the edge. A serpentine won't flop over- its too wide, and can't stretch what way, so all it takes is a vertical wall on the idler pulley to guide it around the radius.

[Flanders 46]

Thanks for the feedback.  The belt size is definitely correct, I've been measuring and adjusting and have a nice collection of belts :) to make sure of this.  The angle could be a touch better, but maybe a degree.  I've also read about running a double v-belt pulley on the alternator (it's 95A), but I'm just not quite sure how to go about this.  I'm definitely nowhere near the 95A load, and I have good wraparound on the alt pulley.   As suggested, one big honkin' PS belt that covers both alt and PS might do it, but this may cause other issues.  Easy enough to check, I suppose -- just gotta buy one more belt and a pulley.  

The bearing seems quiet -- good idea about disconnecting the wires to the alternator (just need to unclip the harness), that's an easy test for the bearings + load.

Half my brain says to go serpentine, but I do like the look of the 'classic' v-belt and fan on the front of the engine.  What have others on here done when upgrading alternators?

[Mach1 Driver 560]

1 hour ago, Flanders said:

 As suggested, one big honkin' PS belt that covers both alt and PS might do it, but this may cause other issues.  Easy enough to check, I suppose -- just gotta buy one more belt and a pulley.  

If you do add a pulley to the alternator and extend the PS belt, let us know how it works out- it would save all the work of a custom idler bracket and be an easy fix. 

Everyone I know with big alternators use a serpentine system. I don't like all the bling.

[RPM 1,190]

If I were you, I'd go to great lengths to get the V belts to work. I didn't even think to try a double V belt when my single belt kept slipping with a ~100 amp alternator. I even used a turnbuckle to tighten the belt. Even though I dislike the serpentine belt look, it does work. 

My need to use the 100 amp alt was a classic rabbit hole affair, which I don't recommend. Since I just had to have a shaker air cleaner, tIhen found it sat too high thru the hood. Shoulda milled the Stealth intake, but lowered the motor. Which required custom motor mounts, engine crossmember, electric fans since stock interfered with lower radiator hose, custom tranny mounts to keep angle correct.

All for a damn shaker. With dual fans, power windows, and stereo, I went big on the alternator. 

In hindsight, I'd keep it stock. Much more simple, and stock works just fine. 

 

[1969_Mach1 333]

13 hours ago, RPM said:

If I were you, I'd go to great lengths to get the V belts to work. I didn't even think to try a double V belt when my single belt kept slipping with a ~100 amp alternator. I even used a turnbuckle to tighten the belt. Even though I dislike the serpentine belt look, it does work. 

My need to use the 100 amp alt was a classic rabbit hole affair, which I don't recommend. Since I just had to have a shaker air cleaner, tIhen found it sat too high thru the hood. Shoulda milled the Stealth intake, but lowered the motor. Which required custom motor mounts, engine crossmember, electric fans since stock interfered with lower radiator hose, custom tranny mounts to keep angle correct.

All for a damn shaker. With dual fans, power windows, and stereo, I went big on the alternator. 

In hindsight, I'd keep it stock. Much more simple, and stock works just fine. 

 

You're right, after all that, it would have been easier to remove the intake and mill the carb pad down, or replace the intake with something else.  Maybe find one of those old stock aluminum intakes that Buddy Barr designed.

You have to be diligent about what combination of aftermarket parts you use.  Some of them can really snowball into a mess.

[dbmac 22]

You might try dropping the belt and spinning the alternator by hand. It should be completely smooth, no gritty/grindy feeling. And freewheel a bit when you spin it.  If its rough, then it's the bearing. If that's good then it may be the belt. A single v should be fine; I have a 100a Tuff Stuff on a single vbelt with no problems.

See pic here: http://1969stang.com/forum/index.php?/topic/81155-i-need-to-finish-serpentine-belt-help/&tab=comments#comment-250121 .

Starting cheapest first, I'd try: 1. Tighten belt. 2. Belt dressing / grip spray. 3. New belt. 4. New alternator. 

New belt and pulley system will be way more than an alternator.

If you do upgrade the belts, CVF Racing makes a serpentine style system with an 8 groove belt but no idler pulley. Or you could go up to a Gilmer style with toothed belt. I bout one but decided not to use it. Plus they whine. For sale cheap if anyone's interested.

 

[danno 128]

OK, let's step back for a moment from the belt issue.  The issue could be electrical with the alternator or elsewhere.  Just because you have a 100 amp alternator, it does NOT mean the alternator is putting out 100 amps when the car is running.  It puts out the amount of amps needed to keep the car running. It could be 10 amps.  I see that you do not have electric fans, and no A/C,  so what is taking all the amps?   The truth is, maybe nothing is taking all those amps, and the alternator is really not working that hard.  Maybe something is taking all the amps that should not be?     

What are your special items in the car that consume all the amps?   Halogen lights can, turn them off.  The A/C can, but you do not have it. A sound system can, so turn it off. You need to find out if your car is consuming a lot of power, and where is it going?   I think you have an electrical problem, espicially when you see the voltage drop when the car is running.   Something is fishy.  

You need to go about some electrical tests, we can help with that.