hi everyone, this is a long shot but here goes. My son was handed down an old Kid Trax 12V ride on car but I dont have power getting to the wheels when the foot pedal is depressed! I've verified the battery has 12.5v getting to the board. There is a gear selector that I've taken apart and cleaned and tested for continuity between the contacts (all fine).
When the key is turned on, all lights work. Putting the gear selector in reverse and depressing the foot switch only makes the relays click...no movement from the motors in the tires. (Motors work by direct connection to the battery). 1st gear selector makes relays click....again no movement. 2nd gear selector cause relays to click and after 2 seconds one tire attemps to spin but it cuts out almost instant.

I've removed all 4 relays from the pcb and tested each one and all 4 open/close when supplying 12v to the coils.

My question is what could fail on this pcb that provides 12v to the motors when the foot pedal is depressed.

Thank u so much!

 

When you checked the relays, did you just check that they clicked or did you test that the contacts opned and closed correctly?

 

I would suspect the battery.

 

I would suspect the battery.

It certainly would be worth monitoring the battery voltage while trying to power the wheels as it may drop a lot when it has a load to feed.

 

If possible get the wheels off the ground and apply 12 VDC power directly to the motor(s). Make sure they run. The board images look like things got hot at one point. Anyway if you can just directly power the motors it will tell you they work. Then as mentioned make sure the relays work, not just clicking but passing full current.

Ron

 

When you checked the relays, did you just check that they clicked or did you test that the contacts opned and closed correctly?

Before I supplied power I tested the NC to the com and got continuity for all 4 relays...approx 1.7ohms.

I put power to the coils, each one clicked and tested com to the NO and got approx 1.7 ohms for all 4...

It seems that the relays are working correctly but Im a DIYer, so who knows!

Thanks

 

1.7Ω is high if that is the actual contact resistance. What does your meter read if you short the leads together on that same range? Then you can subtract that from the resistance readings.

 

If possible get the wheels off the ground and apply 12 VDC power directly to the motor(s). Make sure they run. The board images look like things got hot at one point. Anyway if you can just directly power the motors it will tell you they work. Then as mentioned make sure the relays work, not just clicking but passing full current.

Ron

Lifting the car and depressing the foot switch just activates the relays...i hear a click. Direct connection to the motors via the battery spins them pretty good and fast. Whats the best way to run a full current through each individual relay?

 

The throttle or gear selector circuit is burned out.

 

1.7Ω is high if that is the actual contact resistance.

He's right on that. The melted relay case may have allowed the internals to move and not make adequate contact also.

How are the rest of the terminals connected and do any of them ever have power? You may be able to get some standard automotive relays and wire them up instead... just bring the coil wires up from the board itself.

 

I'm on board with checking the battery. You can check a batterie's voltage and find it at 12 volts. But when you try to drive the car (on the ground or lifted) if the motors don't run then I would suspect the battery voltage is dropping way down. You need to test battery voltage while the motors are supposed to be running.

Batteries need to be kept charged. If allowed to sit for a long time they can develop sulfates on the battery plates. They don't affect voltage but they DO affect the ability to deliver current. That's why I am on board with checking the battery with the motors activated. I think the battery is probably shot.

 

I'm on board with checking the battery. You can check a batterie's voltage and find it at 12 volts. But when you try to drive the car (on the ground or lifted) if the motors don't run then I would suspect the battery voltage is dropping way down. You need to test battery voltage while the motors are supposed to be running.

Batteries need to be kept charged. If allowed to sit for a long time they can develop sulfates on the battery plates. They don't affect voltage but they DO affect the ability to deliver current. That's why I am on board with checking the battery with the motors activated. I think the battery is probably shot.

I wish it were the battery, Ive tried 6 different 12v batteries....2 of them brand new and charged fully. Connecting the battery direct to the motors causes the motors to turn very fast. When the gear selector is put in the fast gear....i press the foot switch and 2 seconds later one tire will spin....only one....and I've got no voltage going to the the other tire. Gear selector in slow speed i get no voltage to either tire, same with reverse switch. Im stumped....i just wish I can buy the entire circuit board somewhere!

 

@Tgillard79 OK, thanks for the confirmation of battery health.

Going off of what others have observed, the relays appear to show signs of heat stress. Though they click - that doesn't mean the switches are making contact the way they're supposed to. Carbon buildup could cause problems. OR the controller controlling the relays may be the point of failure. One other possibility I can think of - check the wires to see they're not damaged or burned. Beyond that - I'd have to put hands on the toy to diagnose the problem.

 

? make one more picture (close up - not too close so it had a good detail/resolution) of the relay contacts at the opposing side of the PCB

 

The photo shows that the white wire has a corroded connector and/or the relay terminal.