MMM gettin really hot lately
 

Thought I'd throw a question out to internetland for you all. Been using a MMM for almost a year in an RC8. Worked great on 4S with a 1512/2D, for the last month I've been using a T8 2250kv truggy can motor. I've had the fan die before, and it's always been fine without it until I could get some new ones. I've been without a fan for about 3 weeks now (trying a different brand) but I need the right connectors to use them. Yesterday I thermalled for the first time that I can recall after about 7-8 minutes of really hard practicing on a medium-large track. Motor 110 deg, batts 88 deg, ESC 190ish but it was probably way hotter as I didn't get a temp very quickly. I was running 15/46 timing low, start power low, punch control off. I thought I might be overgeared so I tried 14/46 for the first qualifier. After 2 practice laps and a hard 5 minutes it came off at 200 deg. I saw that a fellow racer using a RC8/MMM/2650 combo was geared 16/46 and I temped his MMM at 120 right after his run, so I though maybe I'm undergeared, so I tried 16/46 for the next qualifier. Well, it came off at 212deg (BTW, when are these supposed to thermal?). Well, we got rained out so I didn't have a chance to try anything else, but I'm stumped. I had rigged up a fan to run directly off the receiver for the next race but we got rained out. A buddy mentioned that maybe some of the FETs were damaged and the rest are compensating for it, I have no clue at this point. Everything feels normal when driving it, has plenty of punch. Any opinions?

Have you checked the drivetrain for any binding or increased resistance that may have come about recently? Maybe the ESC is totally fine but something in the drivetrain is causing increased rolling resistance putting more strain on the ESC. The problem with that theory is that the motor would be getting much hotter too, and it isn't. Thought it would be worth a check though.

mine did the same thing. next day, MELTY.

Drivetrain is more free than it's ever been. Tekin motor was new 1 month ago. This is my 4th summer racing electric 1/8 (used Quark 125B/ many Neu motors) and I've been into RC since I was 8 (24 years ago) so I am pretty well versed in this stuff. I just don't know the details of how a brushless ESC dies. I always thought it was: running fine, running fine, poof! Do they die a slow death like a rotor losing it's magnetism?

Was this with the stock fan? It could have died and overheated because the MMM's heatsink is rather enclosed and doesn't cool very well without the fan.

ive got mine up to 222 before and it did not thermal, are you temping this outside of the case? if so the inside is about 30 degrees hotter!

It was directly down on the heatsink when I measured. Since there is no fan in there currently, and I dremeled out the fins in the top of the case I have straight access to the heatsink.