It's ALMOST cold... Seat Heater thread

[iNeon]

Last spring I pulled heating elements out of an old Volvo 240 at the U-Pull-It and it is getting colder, so I returned to get the wiring harness-- A bad idea!!

It is tied into this crazy 3" thick bundle of wires that runs from the fuse block, through the instrument cluster, down through the center stack, into the shifter, then to the switches by the parking brake and under the seat tracks(needed a wrench I didn't take to get the seat out...) and then to the seat.

So, what did I do? I cut the connections(a 2-prong dealie) and will build my own harness. This is where I need a bit of electrical help!

The heaters are only set up for a single setting, so I'll just get factory pushbuttons and It'll *appear* to be factory-fitted. Does anyone have a part number for the early pushbutton switch?

I want to use a fuse(or two) in the fuse panel to get my power from, are there empties? Should I run both on a single circuit or build two identical ones to be safe?

I'm not terribly electrical minded-- Do I run a hot wire(a fuse on in the run position) to the switch, and then run that wire to the hot side of the heater element, and then ground the second wire?

This is a little computadora drawing that I've put together thinking this is how it goes-- let me know if it is way off!

[babyjames]

Better be a pretty beefy switch, as those heating elements are going to draw some current. You're better off using a heavy-duty relay to switch the power.

Seriously, you could burn your car (and possibly yourself) up if you don't do this properly. Just go to Radio Shack and tell them what you're trying to do. Chances are they'll be able to design this circuit for you, and sell you what you'll need.

Jay.

[bgkast]

Originally Posted by babyjames

Just go to Radio Shack and tell them what you're trying to do. Chances are they'll be able to design this circuit for you, and sell you what you'll need.

Not if they are anything like my radioshack

[iNeon]

Yessir!

I do want the finished product to look as factory. A trip to the dealership is on the itinerary for tomorrow afternoon to locate switches, and then I will get to working on a better circuit!

It just isn't something that I know a great deal about! That's whyever I'm here asking questions!

So basically, I am to make a single circuit and place a relay between the fuse panel and the switches to drop the voltage?

[Mustang_man298]

If you look inside your fuse panel lid you should see on the tag that a fuse has already been dedicated to optional seat heaters, I would tap off of that. I also agree that the heaters will consume heavy current, and direct wiring to a switch might prove to melt it or start a fire. I would get the factory switch, set it up to control the coil of a relay, such as a generic headlight relay, and wire the seat heaters thru a normally open contact on the relay (would close on energizing) Power to the relay contacts should come from the heater fuse. The switch should be wired from a fused source switched by the ignition, so as to make the relay de-energize when the key is switched off for the reasons that you dont want to have a dead battery, and dont want unnecessary fire risk while out of the car should you forget to turn them off.
Understand I am saying you will need 2 individual circuits here to make it right.
Another thing to consider, my 2003 F350 uses a timer relay in the circuit, to prevent it from overheating and igniting the seat material while driving/sitting unattended while running. Adjustable timer relays can be easily gotten for little cost. You would just use this relay and wire as described above.
-Chris

[bgkast]

I'd just wear sweat pants instead.

[PatricdeBoer]

Originally Posted by Mustang_man298

I I also agree that the heaters will consume heavy current, and direct wiring to a switch might prove to melt it or start a fire.

They'll get really warm then

[iNeon]

So what capacity should I look for in a relay?

Is this where I would get the dual-setting from? Hook the larger current prong on the relay to high on the switch and the lower to the low setting?

I haven't really poked around, but is there room in the black plastic relay box under the hood to mount this stuff?

Anyone have factory heaters in a w116 or w123? Can you maybe take some pictures and such?

[1985 300SD Sady]

Originally Posted by iNeon

So what capacity should I look for in a relay?

Is this where I would get the dual-setting from? Hook the larger current prong on the relay to high on the switch and the lower to the low setting?

I haven't really poked around, but is there room in the black plastic relay box under the hood to mount this stuff?

Anyone have factory heaters in a w116 or w123? Can you maybe take some pictures and such?

Typical Bosch or Bosch-Type 30amp 12v relay will work fine. I would not pay more than $5 for one.

[babyjames]

The relay for the rear defroster has a 30 min. timer built into it. You should be able to get a couple at the bone yard. Take the connectors, too. Should make for a nice, clean install. I don't think the seat heaters on my wagon are timed, but having the timer will decrease the likelihood of fire, and extend the life of the heating elements.

Jay.

[iNeon]

Well-- The last question before I run out to U-Pull-It and grab some rear defrost relays-- Where exactly are they?

Are they under the instrument cluster? In the little black relay box on the drivers inner fender?

I'm going to do this right-- every retrofit I've given the car has really made a marked improvement in useability and the enjoyment of the car! Maybe if it turns out well-- I'll make up a few sets and sell them off to cover my costs

[babymog]

You'll want to set it up with a latching relay circuit. The switch on my 124 & 201 are momentary on and momentary off. This also turns off the circuit every time the key is switched off so that the pass-side can't be left on with no passenger, you'll find that M-B didn't install alternators large enough for extended idling with lots of electrical equipment on and having the seat heaters on when not needed isn't desirable.

- Jeff

[iNeon]

The car idles at 14v, It never really idles for extended periods unattended, I turn it off whenever I get fuel as well. Will these things eat that much current?!?

This is the newest diagram I've drawn up-- I'm just going to go ahead and get the rear defrost relays if enough current passes to warm the elements-- I'll build two identical circuits if that is what is needed to make for a safe install--

So what is a factory rear defrot relay rated at? Should I just go to Radio shack and pick up a pair of new relays instead?

Speaking on rear defrost relays-- My rear defrost doesn't work, the light changes in the switch, but that isn't really related to the circuit working, is it? I'd assume it is internal to the switch and the fibreoptic system, and not so much the defrost circuit? Maybe I'll test out one of the new ones and see if it works then--

[babymog]

My '92 discharged the battery at idle with the bun-warmers and rear-defrost on, and since M-B liked using too small an alternator, the voltage regulator died before 100k miles, add to that the un-switched heated mirrors and it's no wonder I spent Christmas Eve in a fire department garage with a dead 4-year-old $74,000 Mercedes. Good riddance to that car (sold it in '96). The only thing worse than its reliability was the dealer service.

Electrical and charging, I like my Land Rover better than my Mercedes, and that's not good. The rather small alternator coupled with low rpm will discharge while idling with lights and heaters on, it was even cautioned against in my manual.

- Jeff

[lkchris]

DIY will probably cost you more than just buying new parts.

http://www.autowarm.com/