windshield wiper motor and arduino digital pin burn


I need help figuring out why the arduino digital pin seem burnt and how to fix the circuit. There is a windshield wiper motor connected to 2 relay shield, and to arduino. The windshield wiper motor provides 2 wires that are always shorted together except once per revolution when they are disconnected (park function). I connected one of those wires to digital GND and the other to digital pin 12 which I set to: pinMode(12, INPUT); digitalWrite(12, HIGH); It worked somewhat but now pin 12 seem burnt. I tried on pin 2 and now it seem burnt too because it is always low.

Thanks for your help.

Are you sure those 2 wires are isolated from the motor circuit? That contact is normally connected to the -ve supply to the motor to interrupt it on cycle completion.

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.,148850.0.html then look down to item #7 about how to post your code. It will be formatted in a scrolling window that makes it easier to read.

Also a copy of your circuit diagram, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom... :)

Thank you MarkT! You are correct.

Motor has 5 wires. -ground -high speed -low speed -wireA -wireB

90% of the time wireA is connected to wireB. 10% of the time wireA is disconnected form wireB and connected to ground.

If the motor is reversed wireA will be connected to +12 and that would damage an arduino input.

Hi, What model Arduino are you using?

Can you post a picture of your motor please?

[u]Please a copy of your circuit diagram, in CAD or a picture of a hand drawn circuit in jpg, png?[/u]

Can you, with wire A and B disconnected from the circuit, get your motor running and measure the voltage on wire A and then wire B with respect to gnd? This is to see if they at some stage have 12V potential on them.

Most wiper motors have switching arrangements where in the parked mode, a short is applied to the motor to make it stop abruptly.

Also they are wired for "intermittent operation" so A and B may not be an isolated switch.

Thanks.. Tom.... :)