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Old 04-08-2016, 23:13   #1
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Question Overheating Alternator replacement options Perkins 4236

It's been a recurrent theme on my engine. The previous owner had even warned me of it. The alternator heats up too much (85 to 95C) so the Sterling charger goes into overtemp protection. This seems to happen within 30' of constant motoring. At first I though the belt was too tight. I replaced it and it helped but after a while the problem came back. Even with the dedicated fan blowing through a hose right into the back of it, the alternator would overheat. So I give up.
It is probably the original alternator so it had a good life. If the bearings are worn out and making hear, I could get it rebuilt but I'm sure technology evolved a lot in 30 years so I'm considering buying a new one.
The question is: what aftermarket alternator would you recommend for my 4236? I have a Sterling controller but the alternator wires go through a "magic grey box" first which I would get rid of first?

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Old 05-08-2016, 00:09   #2
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Re: Overheating Alternator replacement options Perkins 4236

Any hot rated alt. The issue very likely is the sterling reg is pushing the alternator harder than a Standard automotive reg, and the alt can't handle it. Some smart regs allow you to program max outputs or time...
There are plenty of alts around that will work very well. Balmar are one of the best known, but very expensive. Just make sure that the manufacturers info states that the one you are interested in is hot rated, and suitable size, voltage, and belt system for you engine. Sorry, I don't have specific model suggestions, but it's likely someone else here will.
Oh, hot rated means it can put out its rated output indefinitely without overheating! Most automotive alts are not like that.
Good luck

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Old 06-08-2016, 11:24   #3
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Re: Overheating Alternator replacement options Perkins 4236

First off check for the thread on max alternator temp. You will find that 85 to 95 C is well within normal operating specs. If the regulator is shutting the alt down and the temp is correct (use an IR temp probe to check) then the regulator, temp probe is bad. Most likely (as a wild ass guess) the temp probe.

I have a Balmar 91-100 with a MC-612 reg on my 4.236. It runs under 95 C while pumping out 85 amps full time. Closer to 80 C at 80 amps.

I get pretty much the same from a HEHR Powerline 120 amp alternator.

It sounds like there are some issues with your regulator/temp-sensor rather than with the alt overheating.

As a side you can check out my thread on installing a serpentine kit on my 4.236, see here: Who makes the TAD and SW Diesel Serpintine pulleys?

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