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need help with 12 volt relays? Answered

i just purchased a set of running boards off of a 2011 f150. they are electronic and i need to wire them up to a set of relays. what i am trying to do is to make it so that when the door is open it triggers the relay and powers the motors causing the running boards to open up, easy enough. but the problem i am running into is that when the door is closed and the door ajar switch is no longer sending a signal, i need the relay to then reverse the polarity so that the motor will then spin the opposite direction causing the running boards to fold back up. the motors on the running boards do have built in stops so i dont have to worry about leaving power to them. i am also finding out if the door ajar switch on my 2004 chevy silverado uses a positve trigger or a ground trigger. any help i can get would be much appriciated. thanks


Easy. Here's a circuit that will do it. You need one DPCO relay, assuming your limit switches ARE built in....

Motor relay two ways.jpg

the more i look into this motor im not sure that there are limit switches on the motor. i think the motor just spins till the arms attaced to the motor are full extended. how would i wire it so that after the signal is lost it reverses the polarity for a set time frame then shust power off to the relay? thank you for your help

Try them first, personally I'd fit a limit switch !

Doing what you suggest is possible, but very involving, and might not work right when the motors are cold.


i argree a limit switch is the way to go, i dont think i need a limit switch when the motor pushes the running boards to open, but i do need one when they board are closed. how would i go about doing that, but still have it so that once the door is opend and the power is sent to the trigger wire it would open up the running boards

You'd be better with two switches - things are a lot safer and easier.

Are you SURE they don't have any internal switches ? If they don't I'd look at window motor relays to power them.

Are they "aftermarket" boards or original equipment ?


i dont see anything physical on the out side of the case as a limit switch. so im not sure if its inside the case. what should i look for? they are and aftermarket set up that ford now puts on some of there modles of f150 from the factory. ford has a custom harness with a built in control module, ive email the company to see if i can by just the module and controler. the controler is $92 and they dont list a price for the harness so i waiting to see what they say. id like to do it my self if i can. here is the link to there web page


thanks again

I would guess then that they have a circuit that detects the motor stalling, and then stops driving in that direction.

A power window relay might be the thing you need.

I'm working on it....
I have to say, although I can design you one, I don't know where you buy them from....


ok, i have a granger supply company not to far from me so if nothing else im just gonna pic up some weather proof limiter switches along with the four relays. even with that i figure its gonna run me about $150 to make the harness with all the relays and switches. hoping that the company that makes the running boards will sell me a harness and control box seperate or tell me that there built in limiter switches on the motors and how to wire it, that would make my life alot easier. i know that ever time i run the boards from one position to the other, that the motor seems to still be pushing even after they are at full open or full closed. so makes me think that there arent any limit switches on them. all tho there are 5 wires going into the motor on the ford ones vs. the two on the after marked modles. but then again the ford is intergrated into the factory computer. all im using as of now is the two large gauge wires that power the motor. not sure what the other 3 wires do. wonder if those are wired to an internal limit switch that shuts power of to the relays? thanks again for all your help

Use some PTC fuses in series with the motors, and a fat diode in parallel.