Wiper Speed Control Not Powering Motor

Question:
Hey Doc-
I have an older Tamiya Blackfoot that uses a wiper speed control. When I turn it on, the servo moves the wiper arm back and forth, but the truck doesn’t go anywhere. I’m pretty sure both the battery and motor are good, so I’m not sure what the problem is. Help!

Dave

Answer:
Hi Dave,
The Tamiya Blackfoot was actually one of my first RC cars. I loved it; cool, hard plastic Ford body sitting on the lifted red chassis, big offroad tires … it was great. It didn’t work very well now that I look back at it, but it was still a great truck to have.

The wiper speed control pre-dates any electronic speed controls (ESC), and while it did a good job of sending power to the motor, it did have a few drawbacks. I’ll run down the short list of things to try first – you can probably do all of this with the unit still in the truck, but I would suggest removing it to make it easier. You MUST unplug the battery first, though!

Let’s first inspect the speed control to make sure it’s even salvageable. Are there any burn marks or smell like it’s been burnt? Are the motor wires ripped, frayed or disconnected? If there is any damage to the unit, it may be time to toss it out. If not, let’s move on to some clean-up steps to try and get it back to working order.

• The wiper speed control relies on two metal pieces touching each other to transfer power from the battery to the motor. One thing that might be wrong is that the unit is all gunked up, a very common occurrence. We need an eraser, so find a pencil and remove any build up on the two tabs that the wiper arm comes in contact with. We want them nice and sparkly – like the picture shown – we basically want to get it back to its original state. You want to remove any gunk on the underside of the wiper arm itself (you might have to take it apart to get it).

• Using some rubbing alcohol (ask mom if you’re under 18), pour a little on a small brush (an OLD toothbrush works great) and scrub the bottom of the unit to get all the gunk off of that as well.

Once it’s clean, re-install it back into your Blackfoot, hook everything back up and give it a try. If it’s still not working, chances are it’s dead. At this point you have two options:

1) Try another motor.
2) Dump the wiper speed control and pick up an electronic speed control (ESC).

If you end up needing to pick up a new ESC, I have made a few suggestions below that will last for a LONG time and give you plenty of hours of fun with your Blackfoot! It’s a great truck!

Good luck!
The Doc