Time-Delayed Circuit or Relay?

[l008com]

I recently wired up my aftermarket heated seats to a relay trigged by an ignition fuse. Before that, I had the drivers seat direct wired off the circuit and the passenger seat was not wired. This made me nervous so I usually just used it on low. Now I put them both on high all the time, it's so nice when its 0° out.

One of the benefits of aftermarket heated seats over factory, is that they have physical switches that say where you leave them. In other words, you can leave the seat on when you turn the car off, and its right back on when you turn the car back on. Unlike factory 'digital' seats where you will always have to push the button again.

So these days, it's often in the single-digits. My truck is old (there are no new trailblazer), and it's cranking away in the cold, with all the extra draw of the heated seats. Sure, I can just turn them off. But I'm never going to remember to do that every time.

BUT If I could somehow delay the relay, so it wouldn't trigger until about 5 seconds after it got power, that would be perfect. Ideally some very simple device I could put inline in the 12v+ lead to the trigger pin in the relay that would somehow magically 'delay' current would be easiest to install. But a 30A relay with a built in trigger timer would also work. Do things like this exist?

 

[Deleted member 20902]

There are actually timed relays available! We use them at work all the time but they are 24v. Here is an example of a relay you could use, obviously you need more than 10 amps capacity, however you could use this relay to trigger a larger one. There may possibly be higher capacity timed relays available but I'll leave that for you to research. What you want to do us 100% doable!

https://www.12voltplanet.co.uk/adjustable-delay-timer-relay-delay-on-or-off-12v-10a.html

 

[mrwitty_1]

I actually used NE555 time delay relays to make sequential turn signals on my Mustang. They are inexpensive and are adjustable 0-10 sec but max out at 10 amp so you would have to use it to close a higher amp relay. Check them out.

https://www.ebay.com/itm/DC-12V-Rel...h=item28276f7209:g:gg0AAOSwvD5aKgu5:rk:1:pf:0

 

[Mooseman]

Why not just add a relay that is wired to a circuit that's powered in RUN but not START? HVAC comes to mind.

 

[l008com]

How would I know which are powered and which are not? There are at least three different HVAC fuses back there, would any one of them work for this?

 

[Reprise]

Why not just add a relay that is wired to a circuit that's powered in RUN but not START? HVAC comes to mind.

I like this. Actually, I think a switch (SPST, SPDT) is better. I can think of times when I don't want the seats coming on. But that's me.

How would I know which are powered and which are not? There are at least three different HVAC fuses back there, would any one of them work for this?

FYI - He's not saying *use* the HVAC fuses / relays - just throwing that out for you as an example of something else that works that way.

 

[Mooseman]

I think even the TCCM fuse does this as I use it to power the accessory plugs. Just test for which one works the way you want (power during RUN but not START) and tap it to power the relay, not the seats themselves.

 

[l008com]

Yeah I already have the fuse tap that is the trigger for the relay, not the power for the seats. so its a simple matter of moving it around to use the fuse I want. It's just a matter of figuring out which is which

 

[l008com]

Well I tried moving my fuse tap to one of the HVAC circuits, but alas, due to the shape of the box and the location of the bolt posts, all three HVAC circuits are unusable for my fuse tap.
I tried a few other circuits and ended up with #29 I think, (rain). It does shut off while cranking, but it stays on when the key is in accessory, so that's not ideal.

I don't suppose anyone has a map of each circuit, and when it is on and off? That could be handy for other future mods too.

 

[Mooseman]

Sure, just check my signature for the manuals which have all schematics.

Did you check the TCCM fuse? I'm almost certain it works only in RUN.

 

[l008com]

I see TCM but I'm not seeing TCCM? I was only trying fuses that I knew what they were.

 

[Mooseman]

I believe so. Try it with a test light or meter. Can't hurt to try.

 

[l008com]

Turns out TCM is the one I had left the seats connected to. And TCM does turn off during start, but also turns on in accessory which is not good for heated seats.