by "Tristan" (casselts)
Published 03/27/2017 at 22:47
by "Tristan" (casselts)
Published 03/27/2017 at 22:47
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I’m in need of a latching circuit to activate a light on my dash from a momentary ground signal.
Here’s what I’m attempting to do: I recently performed a 0411 ECM swap on my GMT400 Suburban. This gives me the awesome ability to tap into the newer ECM’s tow/haul mode. It’s a major reason I did the swap since I use the ‘burb to drag the family’s 24' travel trailer all over the place.
The tow/haul mode is activated by a momentary ground signal to a pin on the ECM. Simple ‘nuff. But, I want to hook up a light to let me know that T/H mode is activated... I’m just not sure what the easiest/most cost effective means of accomplishing this would be.
So, how do I make a momentary ground into a constant 12v+ that energizes and de-energizes with each subsequent push of the button?
"Seat Safety Switch" (seat-safety-switch)
03/27/2017 at 23:09, STARS: 0
You are looking for something known as a latching relay. There’s a few circuit diagrams out there that can turn a standard Bosch auto relay into one if you can’t find one off the shelf.
Basically, you feed a relay back into itself so that when the relay’s coil is first energized, it keeps its trigger pin high like the switch was still pushing on that pin.
De-energizing is more of a problem. I think you can set up some kind of reset circuit but I don’t know off the top of my head how that looks. I’m sure there is some chaining of multiple relays that gives you such a magic condition.
Could also just change the button into a mechanically latching on-off switch or something.
"Ike" (untitledcarshow)
03/27/2017 at 23:09, STARS: 0
Huh?
"Tristan" (casselts)
03/27/2017 at 23:20, STARS: 0
I was thinking I needed a latching relay, just wasn’t sure how to make it activate with a momentary ground rather than a momentary 12v+.
"Tristan" (casselts)
03/27/2017 at 23:20, STARS: 0
Which part?
"AMGtech - now with more recalls!" (amgtech)
03/28/2017 at 02:54, STARS: 0
Doesn’t the ECM already do this for you? All of the trucks that use tow mode have an indicator in the cluster. Although, come to think of it, if it sends this signal to the cluster via CAN it won’t work, it would have to be a discreet line. Knowing GM from that time period it could be set up either way.
"VonBootWilly - Likes Toyota, but it's still complicated." (vonbootwilly)
03/28/2017 at 05:55, STARS: 0
Curious what the tow mode does mechanically. I had it on my 2001 V6 Silverado, but I never towed with it and it never did anything different when I tried pushing the button. I wasn’t sure if it was a legit shifting algorithm thing or some GM “innovation” to sell trucks, like drift mode for hatchbacks.
"Tristan" (casselts)
03/28/2017 at 08:11, STARS: 0
From my understanding, it uses CAN to activate the light on vehicles originally equipped with T/H mode.
"Tristan" (casselts)
03/28/2017 at 08:14, STARS: 0
Holds gears longer while accelerating under load and gives quicker downshifts.
"AMGtech - now with more recalls!" (amgtech)
03/28/2017 at 10:11, STARS: 1
Lame. Then I’m afraid I won’t be much help. A matching relay is the way to go, but there are a bunch of variations and I would do a shit job explaining what to get and how to wire it up. Sorry.