M.L. Toys
M.L. Toys
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for smaller 6v vehicles that NEED to be upgraded to 12v.
User avatar
By rachaelchavez
Hi all,
I am a pediatric physical therapist and modify power wheels cars for my kids to be able to have some fun and get around. I was doing well with the 6 volt cars no problem. Simple wiring etc.. but now I am running into some problems with a 12 volt car that has forward and reverse. Also I should note it has 2 motors.

I attempted to add a relay using the instructions from this post:

I wired it just as the diagram showed. When I tested the Ford 150 it worked for the first few seconds and then nothing after that despite anything I did. How could I go from having power and it working to nothing? I am getting frustrated. I previously had it wired with the foot pedal screwed onto always activate and then wired the alternate switch into the hot white line that went to the foot pedal actuator. I was told by an electrical engineer not to do this for safety. So now I'm stuck with a truck that is a mess. Can anyone help me?

User avatar
By wired
Sounds like the relay coil may have failed. Make sure your relay was rated for 12vdc. Can you hear the relay "clicking" when you press the alternate switch?

I'm guessing you no longer have the braking effect by your description of "bypassing" the foot pedal switch.
Thats what I was thinking that the relay went bad. Does it sound like it is wired correctly?

This is the relay I used:

I think its rated for 12 volts?

I do not hear any noise coming from the relay after my initial working point.

What is the braking effect? I removed the pedal, but doesnt the alternate switch take over the same job? When you press the button it goes and when you let go it stops. This is how I have always done it.
User avatar
By wired
Looks like some of the reviewers on AMAZON had issues with that relay failing. You can buy those type of relays (AKA BOSCH style relay) at any automotive parts store or Walmart. If you have power and ground to the relay and you cannot hear or feel it "click" then I would bet it has failed and suggest changing the relay.
If it worked properly at first and you wired it up just like the diagram in the first link you provided then it is wired correctly and you would have the stock braking effect. I breezed through it too fast before my initial post.
Just sounds like the relay failed.
First off, thank you sooo much for your help!

Today I bought a new relay and installed it. The exact same thing happened. It worked for a second and then stopped. I wiggles some wires and got it to happen a total of 3 times. Then nothing.

I tried both relays and now I can hear and feel if I’m holding it the click on both. So I’m guessing it’s not the relay.

Here are my two best guesses at where I went wrong:
1. The battery looks like a 12 volt battery but the label says 6 v so maybe it’s not enough power to activate the relay?

2. I had already removed the foot pedal switch and I just assumed the connections went white, red, orange from top to bottom. I could be wrong and have it wired incorrectly? Maybe I should swap the red and orange wires?

I took some photos of the car and details in case that helps. Now I’m just so frustrated I want to put it all back to the switch wired into the white wire to the pedal as that was working. Is this really unsafe?

I will not fail. I have not given up. Just a bit frustrated, haha. As a physical therapist I never thought I’d be learning so much about electrical, but I’d do anything for these kids who deserve to do what every other kid gets to.
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User avatar
By wired
Yep, it's a 6v battery and a lil f150. You are correct that the 6v battery will not hold the coil on a 12v relay. Drop in a 12v battery or buy a 6v relay. I would upgrade to 12v myself. Those things are a blast on 12v! Here is the pedal switch wiring: ... C_ID=15204

I think you got this!
I worry about it going too fast. These are kids with cerebral palsy and other pretty significant impairments. If I go 12 v won’t it be faster?
I looked at the diagram quickly, if I get a 6 volt relay, do I have to have the brake and throttle? I just want to go from the 3 prong foot pedal to a 2 prong standard female socket.
User avatar
By wired
Yes, it will be faster; much faster. For your application I would highly recommend keeping the truck at 6v.
If you install a single pole, double throw (SPDT) relay you can use your switch in conjunction with the relay to both relocate your switch and retain the stock braking feature.
-Use your switch to activate the relay coil (relay contacts 85 & 86, one needs 6v/+ the other needs ground/-. doesn't matter which one. The coil is not polarized and does not care which is ground and which has power).
-connect stock red wire to common contact (relay contact 30)
-connect stock orange wire to normally closed contact (relay contact 87a)
-connect stock white wire to normally open contact (relay contact 87)

That should work just like stock circuit and you can relocate your switch as needed.

Here is a link to a 6v SPDT relay on Amazon. You may be able to find one locally: ... B00DK899DI

Another option is to use a small separate 12v battery to actuate the 12v relay (which you already have) and still use the 6v battery to power the trucks motors. If you decide to do this, you would still wire the stock wiring to the relay as described above but just run the 12v through your new switch to actuate the relay coil.
Thank you. I bought the relay on Amazon you recommended and I will try that.

Thank you so much for your help! I will let you know if it works when I test it out next week once the relay comes in.
Just to be clear as I think I am confused.

85 & 86 connectors....
I need a white wire that splices into the main positive from the battery to one side of the switch
Then he second side needs to be a combo of the opposite side of the switch and a Black negative wire from the battery?

This would mean I have 2 positive white wires coming off the battery going to the relay?
One goes to 85 and the other to 87.

Sorry I’m a real beginner and I have confused myself so much lately I can’t keep it straight.
Thanks again for your help!

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