Plug Bug: Motor Cooling Ideas and Notes

Electric Bug

Currently, the car is garaged. It has been wet and rainy, and I don’t have the motor water proofed. I tested making it water proof by using some thick plastic underneath the motor area to keep it dry. I used the stuff that you can buy for under you chair when on carpet — Ace Hardware sells it by the foot. After driving home ~25 miles, I touched the motor, and it was excessively hot! Usually I can keep my hand on the motor; it is warm, but not excessively warm. I do have the motor’s over temp circuit wired to a light on the dashboard, but it didn’t kick on, and I have heard that it will only kick on after the motor has reached too hot of a temperature and caused damage.

So, for me to properly water encase the motor area, I will need some other solution. Maybe some slotted venting or something similar to let it still have airflow.

I’m also considering trying to have it automatically turn on a fan after it reaches a certain temperature. I asked about this on the DIY EV forums: Temperature sensor for a Warp9 to turn on fans. has a nice motor cooling kit that I was already checking out, and I might end up getting it or fabricating something myself in a similar fashion. Jeffrey pointed me to the following interesting parts that might let me do what I want:

34-42C NO Temperature Switch

40A Automotive Relay

Ideally, I want to reuse the blower I have for my heater, and have it swap the exit vent to the exterior of the car when I don’t want the heater on. That would allow me to pre-heat the heater with the motor’s heat, and allow the ceramic heater to work less hard.

The blower I got in the CanEV kit is a SPAL 008-A100-93D 12v, multi-speed squirrel cage. I found the spec here:

It looks like it puts out 153 CFM, which is higher than the Jabsco blower sold by EVSource (at 105 CFM) but lower than their Dayton. I’m not too happy with the SPAL blower, as it is a bit noisy, but then again, it is advertised as being “low noise”. I don’t mind the noise as long as I’m driving, but at low speeds I want the car to be dead silent. A few other blowers I found:

It would be ideal if I could use my existing blower to go through the motor and then into my heating system. I want a way for it to automatically come on when the temperature reaches a certain point, and automatically go off when it passes past another point. I can do this with a temperature switch that Jeffrey pointed out, or something like this that another EV’er named Brian did on his car: Brian added a temperature sensor to turn on/off some simple fans. His details on his sensor are here: — awesome job! I wish I knew more about micro-controllers so I could do something like this. Eventually I’ll learn…

For fabricating a blower-inlet box, I think I will take an approach by this guy here. He fabricated a pretty fancy solution, which I like a lot.

So, while the car is out, I took out the Warp Drive controller and mailed it to Netgain. They are going to fix some issues:

* An error code that seems to have just recently stuck on

* Slight bucking/rocking/hiccuping that happens. Sometimes at low speeds, and a reset of the controller fixes the issue. Sometimes it does it under hard acceleration.

* Update the Interface Module — it is showing *higher* voltage when under load (it should show lower voltage)

I also mailed the Lithiumate BMS back to Evolve Electrics to get the software upgraded. Hopefully it will support the Netgain controller via Canbus.

I repaired the BMS with CL-30 inrush limiters and I’ll test it again when I get the controller and BMS back.


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Dan Armstrong

I’m doing a beetle myself, and I’m curious about how you installed the plastic splash-guard. Did you allow air to escape out the bottom rear, as beetle’s are design to handle airflow this way? (with the help of a fan). Do you have pictures with the splash-guard installed? Thanks.


Hi dan,
It was really temporary; I just tested it, and discovered it got too hot. It completely squashed the airflow from underneath to completely keep water out. I’m looking into sheet metal solutions; I may do a version that lets the air escape from the rear, and/or another version that is grated on the bottom to let it always have air flow under neath too.

Are you finding your motor is running too hot? Do you have your bug running yet?


Jay Donnaway

Hi Corbin, great blog, wish I’d found it much earlier, but I don’t get to spend much time on EVDL or DIY EV these days. Anyway, I’ve had great success with my motor blowers. My 9″ motor has no internal cooling fan, just two Vanagon heater blowers with the same outlet size as standard bug heater hose (30mm, IIRC?). Anyway, we fabricated two manifolds with pipe of that diameter (heater box repair part), and clamped the blowers directly to the comm end of the motor. I’ve wired one blower to run any time the controller is hot, just as a safety ‘audible’, and the other is controlled by a tiny thermoswitch that I epoxied to a field coil (just reached in thru the end bell). The thermoswitch is only 70C, could’a been much warmer, as my motor stays very cool, whether barreling up a hill that gains 450 feet in two miles, or drag racing. The thremoswitch signals a relay that is fed by an always-hot wire, so after a hard run, fan #2 continues cycling on and off for a few minutes after I shut the car down..
You can see a manifold here
and I’m just realizing that I’ve never posted a photo of the blowers. Time for a new blog entry!

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