GEM Motor Overheating

I have a 10.5 motor on my '02 E2. I have larger tires and also the 12:1 ? gear ratio. I can only drive about 3 miles in 80 degree heat without the motor overheating. I’m guessing it is a controller reprogram issue. I love my little Tiffany blue gem, but she’s not very useable now. Any ideas from the experts ?

Bypass the thermistor , probably not good idea but since u swapped motors already compatibility could be thr issue , to bypass disconnect the 2 pin connector from motor and jumper together those 2 wires going back to controller , go 5 miles stop touch motor with hand, if fried egg hot it’s bad idea , undo reconnect , LMK…

Hey What controller do you have T-1 or T-2 next question Has the controller been rebuilt? If it has it will have a Blue Sticker on the controller with some numbers possible the date.

It’s very common that after you replace the motor to a larger HP motor that it puts extra strain on the controller if you controller is a stock controller then Most likely you need a Rebuild that’s gonna set you back $450-$500

Please tell us about your 10.5 Hp motor.

I have a 2000 E2 with the same problem although not as severe as yours. Forget the T1 rebuild. I talked to the guys who rebuild them and they said that it would not help heat issues caused by a large motor. I have the 7.5 motor and bigger wheels and was having code 41 on hot days. Look on this site for my solution to the heat problem. Some here argued that I could have left off the copper plate but I think not. See if you can find my pictures of the simple fix I added to my E2 at a cost of about $125.

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Okay, pretty sure it is a T1, yes has been rebuilt/reprogrammed. Original
owner had gel batteries and had it redone for that. My 10.5hp motor came
from Marlon, but I haven’t been able to get ahold of him.

The motor gets EXTREMELY hot after 3 miles. Worked OK for me before, when
I drive mainly to and from work. Now, I’m retired and want to scoot around
like 5-6 miles on a trio, butt can only go about 3 miles before it is hot
enough to fry an egg on!

I completely rebuilt this green with custom paint, upholstery, and have
worked on a lot of stuff (my third gem), but this motor thing really has me

Well I know the tea one controller is not as good as the tea to controller for dissipating heat so that maybe one of your options but most likely reprogramming your current controller to the lower field current and I’m at your current settings could possibly help cool things down. Other options would include a cool air kit and that would be a heat sink that sits on the bottom of your controller along with a fan that tries dissipating heat and some motor scoop vents. If you search this forum you can see where I added some motor vents to my gem. Last but not least would be switching to a 7.5 hp motor. I did the whole programming thing with Marlon and he tends to program on the high side of the settings I found that lowering some of his recommendations decreases performance but adds efficiency and lowest temperatures

I thought the biggest motor you can buy for GEMs is the 7.5? where is there 10.5??? website?

Post the controller settings so we can see what was changed.
Did it always run hot? Or something new?

I got my motor from Marlon, but then he got in a bad accident, so I don’t
know about anymore.

Hmmm, controller settings. It has never been changed, so I have no idea
what they are. Sorry!

and I’m guessing it always ran hot. I just retired, and work was really
close to home, so I didn’t drive as much as now, when I have time on my
hands and lots of beautiful beach to drive it on!

what is marlon? website please? Im interested in a bigger then 7.5 motor for my e6

I will make you a deal on mine. Contact me

Id rather not buy a motor that is having overheating problems haha. Can you please tell me where you purchased it from? Im not sure what marlon is, is that a person on this website? or a company?

Marlon Zendejas of MZ Motorsports

From your link to d&d motor, the new motor will not work properly without being reprogrammed.
“It has never been changed”

My 2007 Gem E2 lives on a small (7 mile long), hilly, Caribbean (80 degree) Island. I have been having a problem with the motor overheating. This occurs regularly on the return trip from town; about 4 miles round trip, as I approach the last hill to get home. The high temperature icon come on and the available power is minimal. I have to wait about 20 min. in order to continue. This appears to be happening at about 130 degrees taken next to the sensor switch (it is hotter on the other end of the motor) and becomes usable at about 100. There is very little temp rise going up hill but it heats up going down so I am equating this with the regenerative braking. I also notice a temp rise when I leave the key on with the car not moving…Any ideas?

I agree the Re-Gen creates lots of heat.
You have 2 different types of Overheat.

First step is to find out what’s over heating.

Is it the Motor or is it the Controller. Example No use adding vents to the hood if it’s the controller that is overheating.

Gem Cool Air Kit

#1 the most common is -41 “Controller Motor Over Heat” if the controller overheats it puts your car in limp mode.

You can add a heat sink and fan to the controller to keep it cool. This Is talked about in a thread here on this Fourm called “Cool Air Kit”. Gem Cool Air Kit

The #2 is actual “The motor gets HOT and overheat’s”
This is from hills and heavy load and slow speeds. You can add vents to the hood and scoops to the sides to draw in cool fresh air.

I recall there being a discussion some time ago about needing a way to turn a fan on to cool the controller but only when going up hill. IIRC, one idea was to use a tilt sensor with a relay so the fan wasn’t making noise and using power on flats where it wasn’t needed.

You need to test and see if the motor is drawing power when key on but not moving . If it is you have a problem . If you have software , remove all of reh plug braking . It is really hard on a Gem going down hills .

I had overheating problem as well, I have a 2002 4 seater, that I have reprogrammed and bigger motor. I created a mount and added 3 mini fans that blow at my controller. I have not had any issue since, however it hasn’t been that hot outside but seems to work for me.