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Replacing controller on rad2go sunbird

 I think my original controller is burnt out so I bought new controller (36V/500W) :

However my original controller (check attached pic) don't have so many connections and names are also different than the ones referred in link.

I can't decide which connections should I do from new controller. I would appreciate any help



The Rad2Go Sunbird's original throttle is a 2-wire non-variable speed on/off type of throttle which will not work with the item # SPD-36500B speed controller. A standard variable speed 3-wire throttle such as our item # THR-35 needs to be used with it.

The SPD-36500B controller also requires a brake lever switch with 2-wires instead of 1-wire and I notice that the original Sunbird speed controller has a 1-wire brake input. The original brake levers most likely have 2-wires which can be rewired directly to the SPD-36500B controller to get the brake switch motor deactivation feature to work. Another option would be to leave the brake lever switches disconnected from the new controller and bypassing that feature.

Regarding the original controller's thin green 'Gauge board' wire I do not have a wiring diagram for the Sunbird electric scooter so I am not sure what type of output it has. It might be a +36V or Ground output wire. I recommend testing the continuity between the green 'Gauge board' wire and the thick red 'Power' wire to confirm if it is attached to it. If there is no continuity between the green 'Gauge board' wire and red 'Power' wire and then it might be a Ground wire which could be confirmed by testing continuity between it and the black 'Power' wire.

This shows how to wire the new SPD-36500B controller:

I hope that this information helps. Please let us know if you have any further questions and also please let us know how it goes. If you have any further information to add to this forum topic such as what the thin green wire output is please feel free to post it here so other people will have an easier time installing new controllers on their Rad2Go Sunbird electric scooters.
Thanks for the info,

 Please let me know if I understood this correctly:

 I definitely need to buy  one of

 And as for brake level I couldn't follow your paragraph if you don't mind explaining a bit about it. I'll probably leave it unconnected.

 Power switch just needs Blue and Red shorted whenever key turned on, I'll connect it accordingly.

 I'll check green gauge wire today and see how/where its connected.

Yes you will definitely need a standard 3-wire throttle such a our item # THR-35 to make it work, the Rad2Go Sunbird's existing 2-wire throttle will not work with the new SPD-36500B controller.

If you want to connect the brake lever switch(s) to the new controller then both wires from the brake switch will need to be connected it. The new controller will not accept only one brake wire like the original controller does. If you connect the brake lever switches to the new controller they should be disconnected from any other existing wires, otherwise a short circuit might occur. The brake lever switches might be wired to a brake light. If they are wired to turn on a brake light then you might want to not connect them to the new controller because they are already wired to that circuit.

From looking at the original controller it looks like the existing power switch turns on and off the power before it reaches the controller's power wires, so the new controller's thin red and blue wires could be permanently bridged together to make the controller always on whenever the power is going to it.

I hope this makes sense. Please let me know if there is anything that you do not understand, or if you have any further questions.

Thanks just bought THR-35WG.
I may have trouble with power switch, by bridge do you mean just short those 2 connections?
I'll check where my key connections are going.


Yes by bridge I am referring to shorting the two connections together. The original controller does not have a power switch connector so it is always on whenever power is being supplied to it. So the key switch has to turn the power on and off before it reaches the speed controller. By bridging the new controller's blue and red wires together it is made to function as the original controller did.

Please let me know if you have any questions.

I've done wiring as per instructions, guage wire turned out to be ground so I connected it to ground and left brake wire unconnected.
Bridged/Shorted Blue and Red wires.

However what should I be doing with output connected? (Black is ground output and red is +36V output) ? How and where should I connect them?



The connector with one thin red and black wire (Black is ground output and red is +36V output) does not need to be connected to anything. The reason I did not mark it as 'not used on the Rad2Go Sunbird'  is because one of its wires could be used for the gauge wire. If you already attached a ground from another source to the gauge then this connector can be left disconnected.

Awesome, thanks.
I think I'm done with all wiring. I'll try to put all the parts together and see if I can start it.
Is there an easier way to test if everything is working? (Before putting on all the parts)


Installing all of the parts and then testing the scooter is the best way to see if everything is working. After I install new parts I will usually lift or block the rear wheel off of the ground and then test the scooter or bike to see if the wheel spins in the air. Then if the wheel spins in the air I will take it outside for a test ride.

I've installed everything but just realized key switch connections are not made.
It seems original sunbird key have 3 connections while all key switches I'm looking at have 2 connections.
Can you let me know how are these connected or link me correct part for key switch.



Most key switches with three wires have two position other than off which are as follows (off-on-lights). If the original key switch has three wires and two positions then the third wire may be for the headlights. Unfortunately there are no wiring directions available for the Rad2Go Sunbird scooter so I do not have anything to reference to know how the key switch is supposed to be wired to the scooter.

It makes sense to me that when the power wires were cut off of the old controller that those wires would have been controlled by the key switch because the original Sunbird controller does not have independent wires on it for a key switch. So the key switch should already be wired to turn the controller on and off unless it has been disconnected from that circuit.

Please let me know how it goes.

Original switch had 3 poisitions, marked: A, B, OFF (I don't know which is what since I never got key from owner).

But if I understood you correctly then controller power connector should be wired to key.


Most electric scooters do not place the key switch between the battery pack and controller because that is a lot of current to run through a key switch. I do not know how the Sunbird scooter is wired though or if its key switch can handle the direct current of the speed controller. If the key switch has thick wires then it might have been wired between the battery pack and controller. The key switch may also have been run through a relay or contactor to turn the controller on and off. Without a wiring diagram I can only speculate though.

If you do not know how the scooter was originally wired then the safest thing to do would be to run the battery pack directly to the controller without it going through a key switch, and then connect the key switch to the controller's small white connector with thin blue and red wires. This way the key switch is only switching a very low amount of current. All key switches can be wired to the controller's thin blue and red wires without having to worry about overloading them.

Please let me know if you have any questions.

You this is what i was thinking, because original key switch has thicker wires (similar to power and motor wires of controller). New switch has really thin wires comparatively.

Even I want to know wiring diagram of original sunbird to achieve what you mentioned in second paragraph, to connect battery directly to controller and run key to controller (Red and Blue wires which were bridged together). However I don't know how to battery routed right now.


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