Throttle connections to Crystalite controller


New Member
Hello all,

I recently had a Montague e-bike come to me for repairs, in hacked up condition. According to the owner, it had stopped working. They ordered a new throttle hoping that would fix it.

The bike went to another person who hacked it up further. It came to me with wires cut and stripped.

The bike has a Crystalite controller 7840E and Phoenix II motor. The person I got it from tried various connections and was not able to get the motor to turn. The control panel does come on.

I have not been able to find any documentation on the controller.

It looks to me as if wires may have just broken loose from the board as flexible, silicone wires were not used.

I’m hoping somebody might recognize the device and know where the throttle connection is made. 3 wires come from the throttle, red, green and yellow, I would like to know their function. Also, is the throttle a potentiometer, signal generator, step controller or what?

The new throttle which was never connected came with no documentation either. I hope somebody can recognize and tell me the wire functions. It looks like something I see on eBay.

I did get hold of somebody at an email address on the controller, he said to replace with a controller, don’t remember which. About $500.

A search on eBay shows many controllers, from $35 and up. I would avoid the low end stuff. Any advice would be appreciated.


Mike Burns

New Member
MOST throttles that have red, green, and yellow wires are designed as follows:

Red = +5V Input

Yellow = Ground

Green = 1-4V Output

Naming convention for Crystalyte controllers: The first two digits of the model are the voltage and the second two digits of the model are the amperage. Thus a 7840 would be a 78-volt/40 amp controller.

I am familiar with the 7240 but have never seen a 7840. A new Crystalyte C7240-GR is $185 from Grin Technologies. They may also be able to help you out with the wiring on the one you have.

I can pull the cover off my 96-volt/60A Crystalyte when I have time and see where the throttle is connected and it may or may not be similar, but I would call Grin first.


New Member
I figured it out with some help from a FB group. What had happened was that a wire or two had broken loose from the board. 2 or 3 people before me had hacked it up and tried reconnecting things, matching wire colors to the throttle. In the process they had connected battery voltage where it didn't belong.
Testing both old and new throttles revealed no output. I took apart the old throttle and the hall sensor chip had burned up, that's what happens when connecting 72 volts to where 5 volts is supposed to go. A new throttle off ebay fixed it and the bike is back to it's happy owner.
I did ride it a few times and it hit a top speed of 47 mph.