W116 Alternator overheating - PeachParts Mercedes-Benz Forum

PanzerSD · #1 03-11-2010, 01:33 AM

In my 78 SEL, I installed a reman alternator in December, 75A.
throughout my day, it doesn't overheat untill I have turned on my fog lamps and leave them on for a length of time, (20 minutes or more) my dash lights dim, tach jumps and engine starts missing (ignition starvation)

Is this going to be a matter of checking/improving my grounds, or upgrading to heavier gauge throughout?

JohnM. · #2 03-11-2010, 02:09 AM

My vote is grounds, grounds, grounds.

280EZRider · #3 03-11-2010, 12:24 PM

Grounding is a good place to start. I would also put a meter on it and check the output. If it was remaned in China, it probably isn't producing anything close to the original required amperage, let alone 75 amps.

loepke72 · #4 03-11-2010, 12:34 PM

Something that got me on both my 450SEL and 560SEL was a bad ground right at the alternator. I was losing .5V across that ground. In both cases I removed the upper alternator bracket and cleaned off the areas that touch the alternator and alternator mount. That restored the good ground there. As far as "overheating", it is normal for an alternator to run hot if the battery is discharged and/or there is a high amount of electrical load. I've seen alternators get hot enough to burn your fingers, but they cooled off after a while once the battery got charged again.