Retrofitting heated seats and illm wire?

Looks like an abbreviation for 'illumination', i.e., the circuit that makes your heated seat switch light up so you can see where it is to turn it on. For the most 'integrated' look, you would find wires that are on the car's dash illumination circuit, the one that is dimmed by the knob on the panel. The wiring diagram (more info) will show you where to find those. If you have a lower trim, you can probably find it on existing unused connectors behind the dash, such as for the headlight washer button in cars without headlight washers.

It sounds like your seat kit wants a positive 'illm' wire, and will reference it to a common ground. I've had at least one car where the dash light dimmer circuit actually went between the lights and ground, rather than between the + supply and the lights. I've forgotten whether my Gen 3 is that way or not ... I must have looked it up in the wiring diagram when I put in the switch for my inverter, but now I'm drawing a blank and would have to look it up again.

 

I wouldn't expect it to be anything complicated; it's probably just a wire leading to one side of whatever light or LED is inside your heated seat switch.

Have you looked closely at the switch itself? Sometimes they have both legs of the illumination lamp brought out to separate terminals, not shared with any of the switch contacts. That gives you the most flexibility for wiring. In some cases, they might assume one of the switch terminals will be grounded, and common one leg of the light to that, leaving only the other leg for you to hook up to a supply some time, which you would have to connect to a +12 supply (or a dimming supply, +12 at full brightness).

Or, they might assume one of the switch terminals will be getting +12, and common one leg of the light to that, so the one left loose for you would have to be connected to ground (or to the kind of dimmer that goes on the ground side of the light).

Now that you have the diagrams from TIS, you should be able to look at the circuits for all the other various dimmed lights in the dash, and that will show you whether the existing dimmer in there is the kind to go between +12 and the light, or between the light and ground.

You've got the primary reference material now that you've got your own year's wiring diagram. Just look up a few of the dimmable lights in the dash and trace back to what's supplying them. If you're lucky there will be some unused connectors behind some of the unused switch blanks on your dash, and the wiring diagram can show you (by pin number and by color code) which wire at one of those connectors will be the illumination circuit. Then you have a super easy place to tap. (I sometimes just extract that wire, terminal and all, from the unused plastic connector, and slip it, terminal and all, into a barrel of a Euro-style terminal block, with a wire off to my added circuit going off from the same barrel. With a little care to insert the original far enough that the screw clamps down on the crimped part, not the shaped part, the car can later go back to fully stock just by clicking that terminal back into its original connector.

In a Gen 4, that would mean a firewall penetration, right? Sounds like too much hassle to me. There will already be at least one heavy wire bringing that in through the firewall to your inside fuse box (wiring diagram will have details); you might find that there is some unused fuse position that will already work if you put an appropriately-sized fuse there, or you might tap off the input side of the box. Doing so, you're already protected by the fuse link on the battery side of that cable, saving you one detail that you'd have to attend to if connecting to the battery yourself.

Knowing the total draw of your seat heater will help make the right decisions....

 

How many connectors and/or junctions do the factory seat switches go through on the way to IG1 No. 4? Are any of those present and easy to reach in your car? Maybe with an empty terminal position at that spot? Get the proper repair terminal from the dealer (see the part number by clicking the {Wire Harness Repair} link in the EWD page for that connector), crimp to your aftermarket seat heater IG wire, click into the connector in the proper position. Elegant and reliable.

Same approach can work for the other circuits.

 

On the Gen 3 (the Plugin anyways) could explain some of the confusion in the manuals, the seat heater switches don't have illm, but they do have on low and on high. It is the same with Gen 4, (the Prime specifically) no light on the switch, but low and hi settings for the amount of heat.

 

ooops, I finally see the seat heater switch lights. 3 lights on each switch, the illm, a low on and a high on.
no more feeling around in the dark to find those switches for me... sorry bout that.

 

Euro-blocks are cheap and work well, and if you avoid crushing the hollow parts of terminals, completely reversible to stock.

 

@mjoo I like the link in your sig Cleaner, quieter engine
I went to the walmart and got a 2 oz bottle of their cheap stuff to use as a measuring container. I'm going to try the formula out in our 02 civic first.
When reading about the research, it brought me back to the days my dad used to feed marvel mystery oil straight into the carbs while running the engine. It would smoke like the engine needed new rings on all the pistons for a few minutes as long as he poured it in slow enough not to stall it out. When my dad did that it would always remind me of the Mosquito Bug Spray trucks that used to go up and down the streets in August.

Thanks for the time and effort you and the team at ls1 put into the research and testing.

 

Hello! Im trying to make the retrofit for gen3 and I can’t find any electrical wire scheme. I bought a second hand interior. From what I see I’m missing 2 Wire from each front seat. Can someone help me where should I connect the 2 wires?