Posted: 6/30/2026 11:01:14 AM EDT
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I’m trying to use an existing switch in my truck to trigger a light bar, due to the logic that GM built into the components it is not doing exactly what I want. Currently in park it works as expected with the button on the dash sending power (signal) to activate a relay I added and power up the light bar, however in drive the dash switch must be held and the signal stops when the button is released. I know that a flipflop relay is able to take a momentary signal and change state, i.e. momentary on then same momentary off. But how would it react to the continuous signal that is sent while in park? I know that normal latching relays can burn out the coils if given a continuous signal, but does a flipflop care? Specifically looking at this module:  
Not much documentation and it is in bad chinglish, if anyone knows of the same functionality from a reputable brand I would definitely be interested. |
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How many watts is your light bar? Those relays are only rated 10 amps, and the description says not to run them close to the limit. 10 amps is only 120 watts at 12 volts. You can always use the relay you linked to control a higher current relay. |
9 lives - 9 pellets... Coincidence?
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Originally Posted By INI: I can make a relay (automotive, Bosch type) latch with a momentary input, but you still need a toggle to break the ground to unlatch. What year/model truck? Yeah I know how to wire up a regular relay to latch, the function I’m looking for is to use the same momentary switch to work for on and off without adding another switch to the dash. These exist and are called flip-flop relays (or bistable relays). |
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Truck is a 2022.5 GMC Sierra 1500 AT4, and I am using a switch that controls the mirror spot lights (GM calls them task lamps in the wiring documentation). In order to use this I had to tap the wire coming out of the lighting control module that powers the left side lamp for my signal to the light bar relay under the hood, I’m thinking I can put a flip-flop relay on that signal wire to get the function I’m after. Also found this on amazon that I think might do the job better than the chinesium one I posted earlier, only downside is it looks to be low (ground) trigger instead of high (+12v) trigger like I think I need… 
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Originally Posted By TX_Critter: Truck is a 2022.5 GMC Sierra 1500 AT4, and I am using a switch that controls the mirror spot lights (GM calls them task lamps in the wiring documentation). In order to use this I had to tap the wire coming out of the lighting control module that powers the left side lamp for my signal to the light bar relay under the hood, I’m thinking I can put a flip-flop relay on that signal wire to get the function I’m after. Also found this on amazon that I think might do the job better than the chinesium one I posted earlier, only downside is it looks to be low (ground) trigger instead of high (+12v) trigger like I think I need… www.amazon.com/dp/B08HSG7YVK You can use another relay off the switch 12v to convert it to a ground signal. Just wire a ground through the contacts. You could also do it with a transistor. To better answer your earlier question about maintaining the input vs. a pulse, the flip-flop will be "edge triggered". It will trigger on the transition from 0-12 volts - actually somewhere in between. Holding the 12 volts will do nothing. Only the transition from 0-12 should trigger it. |
9 lives - 9 pellets... Coincidence?
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Originally Posted By ske714: You can use another relay off the switch 12v to convert it to a ground signal. Just wire a ground through the contacts. You could also do it with a transistor. To better answer your earlier question about maintaining the input vs. a pulse, the flip-flop will be "edge triggered". It will trigger on the transition from 0-12 volts - actually somewhere in between. Holding the 12 volts will do nothing. Only the transition from 0-12 should trigger it. Originally Posted By ske714: Originally Posted By TX_Critter: Truck is a 2022.5 GMC Sierra 1500 AT4, and I am using a switch that controls the mirror spot lights (GM calls them task lamps in the wiring documentation). In order to use this I had to tap the wire coming out of the lighting control module that powers the left side lamp for my signal to the light bar relay under the hood, I’m thinking I can put a flip-flop relay on that signal wire to get the function I’m after. Also found this on amazon that I think might do the job better than the chinesium one I posted earlier, only downside is it looks to be low (ground) trigger instead of high (+12v) trigger like I think I need… www.amazon.com/dp/B08HSG7YVK You can use another relay off the switch 12v to convert it to a ground signal. Just wire a ground through the contacts. You could also do it with a transistor. To better answer your earlier question about maintaining the input vs. a pulse, the flip-flop will be "edge triggered". It will trigger on the transition from 0-12 volts - actually somewhere in between. Holding the 12 volts will do nothing. Only the transition from 0-12 should trigger it. Great, thank you. I only know enough about this stuff to know what components exist and what they (are supposed to) do, appreciate the insight. |
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