reverse sensor disable for towing?

Hello All. I am trying to figure out a way to configure a relay setup so as to disable a pos. ON reverse sensor unit when a trailer is hooked up to a standard FOUR ping trailer hookup. Maybe when a relay senses a ground or positive input from the trailer pig tail indicating that a trailer is hooked up, disables power to the reverse sensor module. The module would come on, or receive a Pos. + input to turn on via a simple reverse light wire splice in. Thanks for your suggestions!

Various methods. Probably the simplest being an SPDT relay with 30 & 87a inserted into the reverse sensor's power path, 86 to sensor power or +12V, and 85 to a trailer socket pin that is grounded (thru the trailer plug) when connected. 30 & 87a are NC (normally connected) until the trailer plug grounds relay 85. If 30 is +12V, 87 could be used for a "warning - reverse sensor disabled: light etc.

I see, i will definitely experiment with a relay and a trailer pigtail. The only thing i an see being tricky is how will the relay know when the trailer is connected if the trailer pigtail pin on the vehicle is already grounded? Just something that came to mind. Thanks!

No - not the trailer GND pin, a "pin that is grounded (thru the trailer plug) when connected". The trailer sockets's GND pin is always connected (to GND). I thought you had it when you mentioned a trailer pigtail - ie, a jumper or loop-back. So you need a dedicated (unused) pin on your trailer socket & plug. If not, there are other ways.

I think i understand. Need to experiment with the info you gave me previously. Thanks!

It should be (relatively) simple. Split it into 2 parts, eg: - sensing when the trailer is attached, & - then stopping or interrupting the reverse sensor. (It take that to mean not the reverse switch since that's needed for reverse lights or cameras or sirens etc, but some distance sensing circuit on the back of the car/vehicle.) The first part - trailer sensing. You have some n-pin socket into which the trailer plug connects. The pins are used for left flasher, right flasher, brakes, clearance/tail, etc, but ONE of them must be a GND pin to ensure the trailer is grounded (forget relying on tow-ball etc connection!). Now, if you have a spare unused pin, you can use that for a "loop-back" connection. EG - a relay has its coil (86) to IGN +12V. The coil's -ve/GND end (85) goes to the unused pin on the car's trailer socket.    When the trailer is connected, a link from that unused plug pin to the plugs GND pin grounds the relay coil and hence energises the relay.    The second part is how we use the relay contacts to prevent the reverse sensor from operating. I reckon it should probably break (interrupt) the sensing circuit and hence be an SPDT relay aka a changeover relay or "5 pin relay" (though I dislike that last name because there are 5 pin SPST aka on-off relays). But more on that later. Let's get the first part first. Use any 12V relay to test, but if you have to buy one, get a changeover type. (As was written on the12volt recently, many gurus recommend ALWAYS buying the changeover/SPDT/5-pin relays. If mere on-off (SPST or 4-pin) relays are needed, just leave one of the 5 pins disconnected. Hence one part fits all. And they are usually the same price - sometimes even cheaper because SPDTs are becoming the norm. SPSTs require an extra production step - namely breaking off the 5th pin!) I reckon I have repeated the obvious, but just in case this clarifies or simplifies the project a bit more, and maybe provides the useful "5-pin for all" tip. Looking forward to how you go. If there are no spare pins, there are other methods. Some add a phono jack & socket or some other connector. Electronic sensing circuitry can also be used, but that has issues (like complication, electronics, solder, maybe reliability...).

Thanks for all the info! The problem I see immediately is going to be that I only have FOUR pins and both the ground on the trailer and ground on the vehicle side are connected to the trailer and vehicle, therefore providing a ground to the trailer via the vehicle. in that case will I need to wire another connector trailer and vehicle to provide a ground. Oh and yes I only need to deactivate the sensors, not lights and backup camera.

You know, the more i think about it.. Would It be out of place of installer's code to use a ring terminal to place over one of the safety hooks from the trailer to provide a ground to trigger the relay to de- activate the reverse sensor? Would like a cleaner way, but this would work...

Apologize Sir for the continued random ideas on this subject, but that is what makes an electronic hobbyist who they are I believe. Now I have another bright idea. I previously wired a switch from up front in vehicle to turn on the back up camera manually via a pos charge routing diodes, so as not to illuminate back up LEDs or back up lights. I believe that would be ideal to wire to a relay somehow using a positive current to disable / disconnect the relay in turn de- activating the reverse sensor which normally receives its pos current from the reverse factory lights. So some how interrupt the wiring w a relay that will disconnect when a pos current input is given to the relay via the switch mounted near the dash of the tow vehicle. Thanks again for your kind help.!

But tresvatos, this is an electrical forum! (ha ha) Random ideas are good. That's brainstorming, and often triggers ideas and solutions from other people. (And to restate business brainstorming rules, NEVER lampoon any brainstorm - no matter how stupid or far fetched. And as one that has sometimes implemented those "ludicrous" ideas, I can take pleasure at ridiculing such scoffers. Not that I would of course, even I respect the dignity of morons.) And okay, you don't have a spare pin. Rats! But yes, any loop circuit would work - ie, something that closes or completes a circuit or path when the trailer is connected. It could be a switch - hence the added phono-plugs etc that some use (but that's an additional hole etc). The only caution is path quality. EG, trailer plugs have their a GND wire because even the tow-ball & socket cannot be relied upon to provide GND. Same with chains, and safety cables that are not rigidly clamped or fixed. A capacitive delay could be added if breaks are intermittent (and relatively short), but IMO that's not that elegant. Anyhow, it sounds like you have the solution to sensing when the trailer is attached - namely your manual reverse LED/lights disabling. It's now a matter of finding how best to disable the reverse sensor, and then interfacing to that switch - maybe via an SPDT relay.