Hello,
I am pretty new here so sorry if this is the wrong place to post this.
A family member recently gave me their child's power wheels type vehicle to fix because it was not working. I got out the multimeter and after doing some tests I found out the power from the battery was dropping out when the switch was flicked to on. Immediately I thought it was the battery, but after getting a replacement it's still showing the same behaviour. So then I tested all the ground wires for any resistance and found one, but after replacing it nothing had changed. I had the ground wire heading into the 'gas' pedal disconnected for testing (The pedal has ground, +6v going in and outputs +6v when pressed down) and when I measured the voltage from the battery again I was getting the full 6v. I decided to plug everything back in to see if things were working and then the voltage dropped again. A little while later I realized when I had the ground from to the gas pedal connected the voltage dropped, but not when it was disconnected. Does anyone know why this happens or how to fix it?

A little insight into how this thing is wired. First, it has two switches, one is on/off the other is forward/reverse. It has two buttons in the steering wheel and two more on the dashboard that just play sounds. The battery is under the seat and power and ground goes out from it to a place where it splits to go to all the other components, then the power wire goes to the switch. From the output of the switch, the power splits to the components going to the pedal, the buttons, and a small PCB that controls the speaker and lights. From the output of the pedal, the power goes to the forward-reverse switch whose output is connected to the motor. Based on what position the forward/reverse switch is in it inverts the power to the motor to go forwards/backwards.

I hope I have provided enough detail and that this is the correct place to post this if you have read this far thank you for taking the time to read my question. If you need clarification or images on anything just say something I will be happy to provide!

 

Does the motor run if you connect it directly to the battery? If it does, then the most likely is a failure of the forward/reverse switch. This happens if the switch is thrown while the motor is running. The sudden reversal creates arcing that welds the switch contacts. Good luck,
Keith

 

Thank you so much for the quick reply - I will make sure to try that as soon as I have the chance. And one question, if the contacts on the switch were welded would it still be able to work sometimes? As when I initially disconnected the ground wire I was able to get the vehicle to drive, but after that, the motor did not seem to be getting any power while the lights and sounds were working. Thanks again!

 

Does the motor run if you connect it directly to the battery? If it does, then the most likely is a failure of the forward/reverse switch. This happens if the switch is thrown while the motor is running. The sudden reversal creates arcing that welds the switch contacts. Good luck,
Keith

That wouldn't explain why disconnecting one of the gas pedal wires changes the battery voltage reading, would it?

 

Thank you so much for the quick reply - I will make sure to try that as soon as I have the chance. And one question, if the contacts on the switch were welded would it still be able to work sometimes? As when I initially disconnected the ground wire I was able to get the vehicle to drive, but after that, the motor did not seem to be getting any power while the lights and sounds were working. Thanks again!

It sounds to me like maybe there's a short of some sort in the gas pedal and, when the wire in question is connected, it's drawing most of the available current from the battery.

If you have a multimeter that can measure DC current, you could test this pretty easily:

• Disconnect the pedal ground wire again
• Set meter for highest amperage range (hopefully 10-20A or higher) and make sure probe cables are in correct position for current measurement.
• Connect one probe to pedal's ground wire connection point.
• Connect other probe to ground wire that was previously connected to pedal.
• Read current value.

 

It sounds to me like maybe there's a short of some sort in the gas pedal and, when the wire in question is connected, it's drawing most of the available current from the battery.

If you have a multimeter that can measure DC current, you could test this pretty easily:

• Disconnect the pedal ground wire again
• Set meter for highest amperage range (hopefully 10-20A or higher) and make sure probe cables are in correct position for current measurement.
• Connect one probe to pedal's ground wire connection point.
• Connect other probe to ground wire that was previously connected to pedal.
• Read current value.

I tried that and it was giving me 13 amps. That most definitely means a short, correct?

 

It sounds to me like maybe there's a short of some sort in the gas pedal and, when the wire in question is connected, it's drawing most of the available current from the battery.

If you have a multimeter that can measure DC current, you could test this pretty easily:

• Disconnect the pedal ground wire again
• Set meter for highest amperage range (hopefully 10-20A or higher) and make sure probe cables are in correct position for current measurement.
• Connect one probe to pedal's ground wire connection point.
• Connect other probe to ground wire that was previously connected to pedal.
• Read current value.

Thank you so much for your help! Will try to repair the switch now.

 

I tried that and it was giving me 13 amps. That most definitely means a short, correct?

Yeah, I'm sure the gas pedal isn't supposed to dump 13A to ground by itself! Does the pedal look like something you can disassemble? Maybe it can be repaired?

 

Yeah, I'm sure the gas pedal isn't supposed to dump 13A to ground by itself! Does the pedal look like something you can disassemble? Maybe it can be repaired?

Yeah, I was just gonna check to see if it could be disassembled, I'm hoping so because I don't think they really sell a replacement gas pedal for this sort of thing, especially now...

 

Yeah, I'm sure the gas pedal isn't supposed to dump 13A to ground by itself! Does the pedal look like something you can disassemble? Maybe it can be repaired?

Sadly I couldn't open up the pedal. But thank you for your help you always replied very quickly and answered all my questions! I can't believe there was that much power coming from a 4.5 amp battery! It could've exploded correct? Or was the fuse the only thing stopping that.

 

Does the gas pedal give proportional control, or is it just on/off? If just on/off, then leave the ground wire disconnected.

 

Does the gas pedal give proportional control, or is it just on/off? If just on/off, then leave the ground wire disconnected.

The gas pedal is on/off. So you think it's okay to have the ground disconnected?

 

If it is on/off, then I see no need for the ground. Yes, leave it off - no one is going to get a shock from a 6 volt battery.

 

I bet the ground connection allows it to coast when you release the pedal. Won't an open circuit motor resist turning? Or am I remembering that wrong? I get mixed up about motors sometimes.

If it does need that to make it less lurchy, we might be able to provide the same effect with a giant diode.

 

I bet the ground connection allows it to coast when you release the pedal. Won't an open circuit motor resist turning? Or am I remembering that wrong? I get mixed up about motors sometimes.

If it does need that to make it less lurchy, we might be able to provide the same effect with a giant diode.

Do you think it's safe to reconnect the pedal? As for coasting I am unsure if it did, but it's not something it neccessary needs.

 

The only reason I can see that the pedal would have a ground is that it really should provide variable power to the motor. It that function has failed, but it still works for on/off, and that is OK for your use, and there is fuse somewhere in the power line, then you will be fine reconnecting the pedal without the ground connection.

 

I bet the ground connection allows it to coast when you release the pedal.

I wouldn't bet too much.

 

The only reason I can see that the pedal would have a ground is that it really should provide variable power to the motor. It that function has failed, but it still works for on/off, and that is OK for your use, and there is fuse somewhere in the power line, then you will be fine reconnecting the pedal without the ground connection.

The battery has a fuse connected to it. Also the power from the gas pedal does not go directly to the motor, it instead goes to the forward reverse switch which does have ground in it.

 

The forward/reverse switch will just swap the hot and ground lines. You're good to go.

 

The ground on the gas pedal is probably there to slow the motor down when it's not pressed, dynamic braking.