upgraded my M936a1 with the delco 33SI alternator

[gstirling]

Did not want to replace the voltage regulator (again) on my original 60 amp alternator, so up graded to the Delco 33si 100 amp (classified section see SS-74M35A2, easy to work with). it is bigger and you eliminate all the operator error issues with the original (improper shut down sequence).
Here's how i did it:
First, the best way to do this is to fab up a new bracket for those's with welding/fab skills. Lacking in both time and skill i took the less elegant path using an all-thread rod and pipe for shoulder support on the mount ears. The install was fairly straight forward, the issue is getting the new alternator pulley lined up with the engine drive pulley. then cutting the shoulder pipe to length to support the alternator tightly (don't want to snap off the cast case ears). The pictures show the differences in the two alternators - size wise the are very similar but the mount ears and the pulley has different spacing. In the picture with the 2 wrenches in an attempt to show how the new/old alternator pulleys are different (the new alternator will sit forward), the bracket is 180 degrees out, the bolt holes should be to the rear of the alternators as shown in the mounted pic.
Wiring is a breeze, old ground goes to the new alternator case ground (can use the original terminations). the hot to the hot, and the old small control wire is abandon. Once installed - so far - the alternator is a champ. right on the tick mark on the gauge. Had to get two new shorter belts - went from the original 3L480 to 3L460 (i.e. 2 inches shorter).

I recommend this swap.

Last note, if anyone wants my old alternator (cheap + shipping) with bad regulator let me know.

 

[74M35A2]

Good job, glad you like it. They are brushless and rated for nearly 1 million miles, 2 remaining in stock.....

Consider to put a second tube sleeve covering the exposed threaded rod portion of your lower long bolt (2nd pic), otherwise tightening that bolt could be pulling that lower-rear ear forward, and will snap it off, depending on the tension on it.

 

[simp5782]

Hopefully you were advised by the seller that the alternator has a 200 degree internal temp control in which it shuts off and quits producing power. You need to cut an air passage for it under the headlight. Otherwise it will quit po producing amps and drain down so you will be stranded.

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[74M35A2]

This is the exact same alternator in use on todays over the road trucks, without issue. You overloaded yours continuously running 6 electric fans including (4 on the radiator, 2 for the A/C). You overloaded it, so it went into thermal shut down, per Delco design, like you overload nearly every inch of your truck. If you are unhappy with Delco's protection strategy to protect their device against your abusive environment, you should take it up with them. They make an oil cooled 50DN unit that may suit you better.

 

[simp5782]

This is the exact same alternator in use on todays over the road trucks, without issue. You overloaded yours continuously running 6 electric fans including (4 on the radiator, 2 for the A/C). You overloaded it, so it went into thermal shut down, per Delco design, like you overload nearly every inch of your truck. If you are unhappy with Delco's protection strategy to protect their device against your abusive environment, you should take it up with them. They make an oil cooled 50DN unit that may suit you better.

The load had nothing to do with it. These trucks do not have much airflow thru the radiator which doesn't help a truck. Like a wrecker that will be pulling hills long and slow and getting hot cause the fan clutch doesnt kick on all the time. Like right now. No load on the alternator at all. No fan clutch on. Pulling a 6 percent grade for 5 miles even with better air flow it drops to 25.5. Kick the fan clutch on itll jump back to 27.2 when the engine temp drops to 180. The lack of rpm doesn't help either. Itll drop voltage more than that if I let the temp climb to 210 or more. The alternators proximity to a 240+ degree oil cooler doesn't help along with the block temp. I believe the air flow that gets between the oil cooler and alternator helps best. Its location doesn't get good flow of air at all.

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[74M35A2]

They do have temperature compensated voltage regulators, the higher the temp, the lower the voltage, and vice-versa. This deliberate, and is to keep the batteries from boiling (can use higher charge voltage in lower temps to recover batteries quicker).

 

[simp5782]

This would be further addressed on a wrecker with it having to cool the transmission, oil, and itself while using its crane unit. It Is suppose to have a fan clutch control so that when the power divider is on it turns the fan clutch on but not all got the mwo done.

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[gstirling]

SIMP5782 - there was a MWO that added (or can be added) that engages the fan when the crane PTO is engaged? i can see how that can be done with a second air supply around the shutterstat to the clutch using the same air from the auto throttle. Any idea which MWO it is? (guess i can google each of the tags on my truck and see what they are, and probably should anyway...LOL). my truck seems to run with the fan engaging only on long hills and if running the crane PTO on a hot day, for a long period, it will cycle every once in a while. I don't pull heavy loads (M1061 trailer) with a few tons of logs.

I think i will put a cheap remote air temp guage (temporary) under the hood next to the alternator and see just what the alternator sees air temp wise. I would have thought the fan windmilling would be sufficient for the alternator cooling when on crane PTO... but that engine is a 200 degree hot chunk of iron...

 

[simp5782]

SIMP5782 - there was a MWO that added (or can be added) that engages the fan when the crane PTO is engaged? i can see how that can be done with a second air supply around the shutterstat to the clutch using the same air from the auto throttle. Any idea which MWO it is? (guess i can google each of the tags on my truck and see what they are, and probably should anyway...LOL). my truck seems to run with the fan engaging only on long hills and if running the crane PTO on a hot day, for a long period, it will cycle every once in a while. I don't pull heavy loads (M1061 trailer) with a few tons of logs.

I think i will put a cheap remote air temp guage (temporary) under the hood next to the alternator and see just what the alternator sees air temp wise. I would have thought the fan windmilling would be sufficient for the alternator cooling when on crane PTO... but that engine is a 200 degree hot chunk of iron...

That is my alternator temp. At idle. Fan clutch on with a 7amp draw. Engine block at 180. Oil cooler above it at 166. And 68 ambient temp

You can install a Horton fan clutch solenoid. This gives you a thermal sensor to mount in place of your stutterstat location and you can choose a higher temp as well. This solenoid allows you to install a manual switch override as well. So you can shut the clutch off on long hills to maximize power then it also allows you to turn it on for downgrades so you can use it as an engine brake

You have a wrecker that weighs 40k +. That is the equal of any other 923 carrying 10tons in its bed or a 934 with 5tons. It's a load on a 939 truck.

https://www.steelsoldiers.com/showthread.php?t=169313

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[gstirling]

yeah when i got the truck i did that weight math... and figured that's one reason my truck is soooooo slow and why i get to pay extra each year for a 44k lb. tag. LOL
i've only run the truck for a hour or so since the alternator install on the crane PTO so that did not load up the truck heat wise. will see what i get temp wise here in a bit. Or if a simple heat shield between the alternator and the block would measurably help. did that on several old chevy's to keep starters from cooking (exhaust headers close by). as a last resort could reroute the upper head cooling return line a bit to allow the alternator to sit up and away from the block might allow it to run measurably cooler? take some fab work for a proper support bracket and some creative new tubes in the cooling system to run it neatly out of the way. but will see if i hit any temp issues first.