Code -41

I have a 2000 two seater that gets a code 41 almost everytime I use it during the summer hot days. I also live in a hilly area and along with the 7.5 hp motor and larger wheels, there seemed to be not much hope for a cure. I have cut the thin aluminum firewall behind the T 1 controller and will install a 1/2 inch thick copper plate that is 7 by 10 inches onto the aluminum frame. Then I am going to bond the controller to the plate with screws and sink grease. In the picture of the frame between the battery and the controller, I am going to mount a small muffin fan that will blow air from the outside onto the back of the copper plate. I wanted to use a liquid cooled plate but they are too expensive and the available space was too limited. After I get it finished I will post the results of this modification. Click on the pictures to make them larger. If this works it will be a good fix for less than $200!

Drop your tire diameter or install a 12.44 gear box. A 2000 has an 8.9 gear box. Good for flat land and hot rods - no good for hills.

Your probably wasting your time with the copper it makes a good heat sink but you need something that will radiate the heat away from the controller… The finned heat sink used on the 6 passenger will help some but with the gearbox you have and the large tires you will still get 41’s.

Make sure you use heat sink compound or at least grease between the controller and mounting surface.

There are only so many times you can do a 41 before the controller pukes.


I agree. A finned aluminum heatsink with fan may help.

Put one on my brothers. Easily found on junk electronics.

Cu on al just seems wrong.

Copper is 50% better at heat absorption than aluminum. It may not work but I am going to try it. I think with the fan it may solve the problem. If not I am confident that I will get more range than I get now in the summer days. This was a terrible design flaw that with normal NTSB laws would probably be a recall. The GEM car is a rolling disaster and under normal circumstances, it would be banned. I have contributed to the problem by buying into the Ride-4-fun lie about having it all. As with any car if you put in a big engine and then do nothing about the original brakes or cooling systems, then you are setting yourself up for a big letdown. I would like to have a lower geared drive but I haven’t been able to find one as a swap. I have the high-speed gear box for flat land and I live in a hilly area and would like to have the lower gear version gear drive. I am doing what I can to overcome a poor design without spending a ton of money.

What size tires do you have?

You would be way ahead to cut a heat sink out of this.

XL Large Black Anodized Aluminum Heat Sink 11 75 x 11 75 x 1 625 in 300 x 40 Mm | eBay


I finally received my piece of copper plate and the finned aluminum heat sink. I mounted the copper plate to the back of the T 1 controller and then mounted the finned heat sink to the copper. The heat sink came with a thermoconducter gasket which I used between the copper and the aluminum heat sink. I fabricated a piece os sheet metal to cover the recess between the bottom dash brace and the top brace behind the top front battery. I bent the outboard end of the metal strip to hold the small 12 v fan that will blow into the recess. I left a space at the sink end so that the air blowing over the sink fins could exit near the windshield wiper motor. Then I mounted an on/off switch on the panel in the cab. I took my wife and drove the exact same route that I did two weeks ago and then I got a code -41 but this time I did not get a code and I used the street setting more than the turf setting. I ran the fan the entire time and I can feel warm air coming out of the area near the wiper motor. I do not know if this will eliminate the code 41 but it worked today and seems to be a simple fix for those of us with the old T 1 controllers. Below are some of the pictures of the parts and installation. The copper plate was the most expensive at $160 for a 6 x 10 x 1/2 inch piece. The fan was $5 and the metal sheet was a piece of scrap that I had. I covered it with the sticky backed auto insulation. Click on the pictures to enlarge them.

1 Like

Heat sink and fan is a good idea.
However, copper and sheet metal don’t play well with aluminum. In the presence of moisture and batteries, it is not a good idea. Mechanically or electrically. IMO
Very little surface area compared to your finned aluminum, made for the purpose.

Probably better off to eleminate the copper and mount the finned heat sink directly to the back of the controller with the heat conducting gasket.

inspectorudy, Love your work.
I understand the cooper plate, you are sinking 100 times more with that heavy plate, the the finned aluminum and fan is just dissipating heat from the plate.
Love it.

There is no contact with any sheet metal. The metal wall is stainless steel and the copper plate only touches the frame’s aluminum in two small places. The copper plate absorbs so much heat from the controller that you cannot believe it. The finned heat sink then helps carry that heat away from the copper. If I had gone with only the finned heat sink then all of the unvented heat would still be in the controller and I would have had to go to a much larger fan. This way the copper soaks it up as fast as the controller produces it. I have done some auto body welding and when I wanted to not damage the car skin I used copper behind the weld and it worked great. I’m sure there are some scientific things that I could have done better but I used what was readily available. The copper plate was by far the hardest to find and the most expensive. A funny thing is the plate came by UPS in a big cardboard box and it sat in my foyer for a day in air conditioning. When I opened the box up the copper was still hot from the day before being in the UPS truck. That gives you some idea how much of a heat sink thick copper is.

Think about this. The heat is absorbed by the copper plate. It is then radiated to atmosphere by the finned aluminum plate. The question here is: Why would you want to store the heat before transferring it? Why not transfer the heat as its generated? Mount the finned radiator direct to the controller with the heat transfer gasket

You eliminate the ineffieciency of the dry joint between the copper plate and the controller, and the copper plate itself.

Much quicker heat dissipation for the controller.

What say you?


Well, the plate and the controller are bonded together with high temp grease so they are pretty efficiently continuous. The copper has a much higher thermal transmission rate than aluminum and therefore will absorb heat much faster from the controller than they finned aluminum piece would. And finally, the heat absorbed by the copper plate allows the controller to stay at a lower temp than if there was only the finned heat sink attached to it. As I said before, if all I had was the aluminum heat sink it would have to have a much stronger fan to remove the heat from the controller and even then it wouldn’t be as quickly.
From a heat sink designer:
The best practical coolers have a copper base, usually heatpipes, and aluminum fins. Copper is better at heat transfer and aluminum, because it is much less dense, is better at heat dissipation, so good heatsinks have a copper base that quickly/efficiently gets the heat away from whatever is being cooled, heatpipes that quickly take the heat away from the base, and the heatpipes are attatched to aluminum fins that quickly dissipate heat. Some coolers are just a block with a copper base and aluminum fins. The aluminum absorbs heat away from the base and dissipates it at the fins.

I did not know this but was using the knowledge I gained from school many years ago. Like I said, copper is the quick exit path for the heat in the controller and then the aluminum is the exit path for the heat from the plate into the air. I tried to find a liquid cool plate but the beer plates were too large and one that would fit was over $400 plus the radiator and pump system. I appreciate the discussion about this and hope it will help someone with a similar problem. For less than $200 I am a happy GEM owner!

It’s a matter of thermal resistance. Anything between the controller and radiator has less than zero resistance. Raising, not lowering temperature.

It’s only the principle, in practice, it will work just fine.
Remarks are just to save someone else the expense of an unnecessary cu. plate.

I look at the copper plate the way I would look at a holding pond for the heat from the controller. If we had a home that was slowly flooding and hooked up a pump to pump out the water the pump would only be able to pump so many gallons per minute out of the house even as more water comes into the house. But if we had an empty holding pond next to the house then much more of the excess water could flow into the pond, through the doors and windows instead of just the pump hose, at a much faster rate than the pump could evacuate. It may not be the most efficient way to do it but I know that the copper will allow much more heat into it than the aluminum fins can dissipate. Just like the heat sink maker said, copper is the preferred sink and then aluminum fins to dissipate its heat.

Not so. The heat sink loses heat faster than the copper plate absorbs it. If it didn’t it would build up in the copper and trigger the 41 code. That’s why they build the finned units.

Copper is a real good heat moderator and is used to absorb and moderate temperature fluctuations in a brick form as you have done.

However as a dissipater of heat it has to be in a finned configuration. Think finned automobile radiator

if you hadn’t added the finned unit the heat in the brick would have finally risen to a temperature to cause a 41.

There is not a thing wrong with your set up. The copper brick is just redundant.

The best little tool to analyse this is a IR heat gun with the laser. Got mine at Harbor Freight for 34 bucks.

Amazing: I got it because I play with programming and need to check motor temperature with different settings. It will also tell you which brake is dragging even when you don’t think they are.

Yes I also use it to chase down 41 codes.

I agree. A better analogy of the water would be a pump and a sponge.

The sponge is best at soaking up water, and good at moving water to the pump sump.The pump can then remove the water.

It’s a great sponge. It can suck up the water faster than the pump. It can hold more water than the pump sump.

For short time periods it can keep things dry without the pump. Some water will even evaporate.

No matter how big the sponge, in time it will saturate. No matter how porous it will slow the flow of water to the pump. The total water removed will fall to the pump after saturation.

Wait! I’m confused! These cars got water and water pumps in them? Lol. This stuff is way over my head! ( poor little retired school janitor brain)!

I disagree with you about the copper although I think the sponge analogy is a good one. The copper is the sponge that wicks away the heat very quickly and if the finned sink wasn’t there it would eventually re-enter the controller. But the copper can absorb heat faster than the aluminum sink can dissipate it because of the fin square inches and the fan size. Without the copper the ability of the fins to dissipate the heat would depend on the fan and the square inches of fin surface area. No matter the reson for the heat loss, the copper is the sponge that helps relieve the controller heat quickly. and its capacity to absorb a lot more than the controller makes it the escape hatch for the finned sink to work without having to be rated to cool a certain amount of heat quickly. If I were a thermodynamic engineer I could calculate the finned area and fan size to eliminate the heat from the controller but I’m not. If one of you wants to try your theory then you do the test with just a small aluminum heatsink and let us all know the outcome. BTW, I have the 7.5 hp motor and the 14-inch wheels and live in a hot very hilly area.

Don’t fight success:)