Hey all,

Looking for advice on cooling my alternator, and to share some really useful things I've learned.

I have a Universal M-35 A version in my 1996 MK II. I installed a 100 amp Balmar alternator and the MC-614 regulator since I have lithium batteries. The setup works great except that it is really prone to overheating. With the MC-614, I can set the max temperature before it starts self-regulating and reducing load. I called Balmar and spoke to an excellent tech (best customer service for any company I've ever had btw, and they are a great resource!). So as per their recommendation, I set the max temp at 90 degrees C.

Also, even though I know a lot of people here have recommended using the small engine mode, he cautioned me away from that. Apparently, it works by falsely triggering an overheating alarm which cuts output to half. The issue is if your alternator actually manages to overheat for whatever reason while this mode is engaged, you won't know because it will already say that it's overheating, and you have to manually reset the alarms each time you use this mode. 

The issue comes with the engine cover on (mine has 1-2" of soundown installed to reduce noise, one of my better upgrades, instructions on how to do this are found on this site easily). The temperature slowly climbs until it hits 90 degrees and then the regulator throttles me to about 50-60% field output to maintain 88-90 degrees. However, if I take the engine cover off, I can run it at full output and it never goes above 75 degrees! The issue, I've decided is I need more ventilation around the alternator.

I tried routing the exhaust blower ventilation duct to suck air directly from behind the alternator, and placed the passive intake output ducting near the fuel injection pump to try to get a flow of air over the alternator, but this made absolutely no difference. I will try installing a second blower on the intake to actively pump fresh air in, but also expect this to make little difference.

My next idea is to install two 120mm computer fans on the starboard side of the engine cover to pump in fresh air directly onto the alternator. As you may know, balmar alternators suck air from the sides of the alternator with two bidirectional fans and expel the hot air both forward and backward. I plan to install a regular household HVAC register that can open and close since it's almost the exact same size as the two fans. This will allow me to run my alternator at 50 amps most of the time with the register closed and fans off to maintain as much sound insulation as possible, but then I'll be able to turn on the fans and open the register when I run my engine in "generator mode".

One other concern I have is the alignment of the belt and pulleys. At first, I had terrible alignment and was producing lots of dust (and hence probably heat in the alternator bearing). Counter to most people's recommendations, I have foregone the $500 balmar serpentine belt upgrade and am using a regular v-belt. However, with a thick non-toothed agricultural tractor belt, I've run over 20 hours of this alternator at full output with no issues, so I'm waiting to do this upgrade only if I have to. I noticed that the hole where the bolt goes through the alternator and the alternator bracket was elongated in the alternator bracket. This means I have to do my best to hold the alternator in the correct position while my girlfriend tightens the bolt and hopefully I have the correct tension and alignment. It's not the best, but it seems to reduce dust and friction and therefore heat. I have considered having a machine shop fabricate a better bracket, but am not sure how much of a difference this would make. The only thing I'm scared of is if my current bracket breaks and I don't have a spare I'm pretty screwed. Has anyone found a good solution or source for a new one? All I can find is this $650 ripoff. Does anyone know if a kubota dealer would have this?

I will post photos and updates on this project when I get to it later this month. Before I do, does anyone have any experience successfully cooling their alternator through any other means? Hope this was helpful for others!