Gem overheating problem

I’m trying to use a gem for strip spraying weeds in an orchard. I would like to keep the speed at a constant 2 to 4 mph but it seems to be overheating like that. It puts up the code for overheating ( can’t remember the number right now) . I converted it to 20s and had the controller rebuilt. The weight of the sprayer full and me are about 500 lbs total… Any suggestions on keeping it cool?

It would help if you let us know more about your car, any additional mods(besides the 20s), and a few more bits/observations so we can make an educated guess.

What is overheating? Motor or controller?
Who did the controller rebuild?
Any programming changes?
How long are you spraying before you get the code?
What is the code and is it always the same?
Are you in turf mode?

No mods besides the 20s. The controller was rebuilt by flip. No changes to it. The code was 41. When the code comes on it starts slowing down and if I let off the throttle it quits completely until it cols off. The motor has new bushes. It seems sliuggish taking off ant top speed is 20mph.

I’m spraying for about a half hour before it gets hot. The motor does feel pretty hot to the touch . I’m not sure what turf mode is. Is that the lower gear that only let’s it go about 15mph or something else

Yes- turf is low speed. It tells the controller to use a different set of numbers to control your motor. Without knowing what is programmed in there I cant say if it will make a difference, but since you aren’t needing high speed give it a try to see if it acts different.

Code 41 looks like controller overheat. I would think that is related to a high speed(big current) thing but maybe you are still using quite a bit if surging, going uphill and possibly the controller is working harder just going slower? Coupled with no airflow related to going fast this may be an issue.

When you removed the controller there may have been some sticky paste on the bottom. When you remounted the unit did you put more back on? It uses the plate underneath it as a heat sink. For those who use their cars in hotter/desert conditions I’ve seen pics of an aftermarket(factory?) finned aluminum extrusion with fans that go under the controller for extreme heat conditions.

  • Just guessing since you still haven’t fully described your car.

Thank you. I will try some of those ideas. I didn’t put any paste back on when I put the controller back on. Do you happen to know where I could get the heat sink/ fan ? It does get pretty hot around here.

Dragging brakes. Measure temperature with an IFR heat gun

He’s using the car in his orchard as a transport for his sprayer. He only does 3~5 mph.
Would dragging brakes still cause a -41 problem going that slow?

Yes, we had this exact issue looking at Christmas lights a few years ago. One of our rear brakes wasn’t releasing completely. We were driving slow without a great deal of air movement, and I couldn’t tell the brakes were dragging. Our 05 e4 kept throwing the 41 error.

After checking the usual suspects of dragging brakes, loose wiring, corrosion on terminals, and the controller being secure to the plate, I would still recommend a heatsink if you are going to be doing lots of slow moving driving with a large load. Check out: Controller Heatsink Upgrade

@RS_E6 went with a beast of a heatsink, and I think it looks awesome on top of the function :grinning:

A heatsink can be purchased from 10.080" Wide Extruded Aluminum Heatsink - HeatsinkUSA


I believe there was a factory heatsink plus fan option for the earlier GEMs. I’m not sure if those kits are still available. Heatsink USA has another heatsink that is of similar dimension but the fins run perpendicular to the one I installed. If your controller is mounted front to back (versus side to side like mine) I’d go with the other heatsink for proper airflow. That’s my theory anyway, I haven’t done any kind of airflow testing to confirm the theory. I just know I never received another overheating error after installing the heatsink.

This is very interesting! I will have to keep an eye on the rem pile at my local metal supply for these extrusions.
If they can’t be found elsewhere and there is enough interest I might be talked into knocking out a couple.

Agreed, I have seen about half and half on all the GEM’s I have worked on. I think most of the E6’s had sinks, but I have seen factory sinks and fans on many E4’s as well. I don’t know if it was an option or just certain years/models.

For sure. If brakes are ok Got to a 14.76 transmission and smaller diameter tires (21inch) we dont know what year present gear ratio or tire diameter.All are factors.

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Thanks a bunch guys. These are all good ideas. I’ll start working on them.