Adding Front And Rear Seat Heaters

[Squiggle Dog]

I used to have a 1979 300SD parts car that had front and rear heated orthopedic seats with headrests, front and back. I removed every part of the seat heater system that I could find with the intention of installing in my daily driver. I sold the complete assembly for $50USD to someone who wanted to install the parts in a W123 coupe. I later regretted the decision!

The buyer ended up not needing some of the parts, so I bought everything back except for the front harness and heat pads. Someone is parting out a 6.9 and is pulling the front harness for me, so I believe I will have all of the parts I need to install in my car, except for the heat pads--however, I have a set of front and rear pads from a W126 that may or may not fit.

One thing I am wondering about is if there is a relay cube, thermostat, or computer that regulates the heat, or if the switches do everything. Is it as simple a system as a wire harness connected to an auxilliary fuse box with an orange switch to power the heat pads?

It just so happens that the B-pillars with switches for the rear seat match the color of my interior (bamboo). I'm converting the power windows to manual so I have installed a nice zebrano wood center console piece without window switches. Unfortunately, I will have to cut holes in the console wood for the seat heater switches. Looking at the back of the console wood I can see one square hole in the plastic backing through which I can see where the hole would be punched out for the seat heater switch to go. I do not see one on the other side, but maybe there is a "punch-out" in the wood behind the plastic backing. Looking at the console piece the seat heater switches came from, it appears the holes were made by drilling a hole at each corner then "connecting the dots" by cutting between them and making a square. I will be very, very nervous to make the holes for the seat heater switches!

[WGB]

My car has them fitted.

I also had new pads fitted which is probably a safety if not a practical issue.

The switches have two positions - single dot is low heat and two dots (and the light in the switch comes on) is full heat.

I don't remember there being any relays in the system but there is definitely a harness as each heater will require three wires to allow for the dual heat ranges.

By the way - they are very effective.

And yes you have to make your own cutouts in that beautiful woodwork for the front seat switches.

Bill

[Big_Richard]

My car has them fitted.

I also had new pads fitted which is probably a safety if not a practical issue.

The switches have two positions - single dot is low heat and two dots (and the light in the switch comes on) is full heat.

I don't remember there being any relays in the system but there is definitely a harness as each heater will require three wires to allow for the dual heat ranges.

By the way - they are very effective.

And yes you have to make your own cutouts in that beautiful woodwork for the front seat switches.

Bill

did you replace the pads Chris put in the car?

Those were aftermarket duel circut heated pads like the OEM ones, and i soldered the MB switches onto the aftermarket harness's for him 

[WGB]

They were the aftermarket pads Chris purchased (That you presumably soldered - thankyou MT) but they were not all fitted at the time and I refitted them all when I re-upholstered the car as some of the previously fitted pads were not quite where they should have been under the covers.

I should have more correctly stated that "new seat heating pads were fitted to my car" as I would not be quite so happy with 30 year old heating pads sitting on highly inflammatory coconut fibre and recommend replacement as a realistic safety feature.

I don't know what Chris paid for the pads but they sure work well and they seemed quite robust and fitted well.

Bill

[Squiggle Dog]

I know that the W126 and later use a relay module and I've been trying to figure out if the W116 had them or not. The guy who is pulling a front wiring harness for me says he saw no relay, so maybe there isn't one.

The heat pads I removed from the W126 look to be in good condition and I am hoping they will work (and with the dual setting switches). Instead of being square like the ones like my W116 parts car came with, the W126 pads are strips that slide under the pleated sections of the seat, between the padding strips and the leather/vinyl skin itself. The connectors are the same.

Currently in my possession are the W126 heat pads (with plastic eyelets), W116 B-pillars with pods and switches, small underhood fuse box, rear seat wiring harness from the small fuse box to the pillars and seats, and three additional switches. The front wiring harness is on the way, so in theory I should have everything I need to convert once the front harness arrives!

My front seats are as broken as they can be. The springs are completely flat and the skins are shredded. I have 2 good sets of springs that I will use and I think a spare set of skins for the driver side. I think I will place the W126 heat pads in there while the seats are apart. At least that will get me by until I have some new skins made (in custom two-tone MB-Tex) some day when I am rich and famous.

I've also got a lead on some genuine W116 privacy curtains locally that I am considering installing. We'll see how this pans out. Eventually I will have a 300SD like no other, especially if I decide to install the 5-speed manual transmission!

[Squiggle Dog]

I used to have a zebrano wood suspension switch housing that mounts on the console and I was considering removing the suspension switch, installing a black piece of plastic in the gap, and installing the seat heater switches in the plastic. But, the suspension switch and housing went to a better home where they will be used as intended.

[Papalangi]

Cutting the Zebrano scares me a bit.  The high gloss finish like probably going to chip unless you take care to prevent it.

I don't know that any of these suggestions will work but it's how I'd do it.

From the backside, drill small holes, 1/16" or so, in each corner.  Be very careful as the drill breaks through, holding a small block of wood against the finished side may prevent tearout.
Using the utmost care, scribe a line from hole to hole with a new Xacto.  This is an attempt to control chipping so score through the finish but be careful to not lever the blade side to side.
Carefully open each hole enough to slip a coping saw blade through, teeth pointing toward the finished side.  Use the finest blade you can find, you'll be looking for pin end scroll saw blades.
Saw slowly and carefully, applying sawing pressure only on the cutting stroke and being careful on the return stroke as the saw teeth have a set and will tend to lift the finish.
I thought about putting blue masking tape on the finished side but decided that it would pull the finish off when removed.

Michael

[Squiggle Dog]

Thanks for the tip! I will need all I can get when the time comes. Maybe there is an expert switch hole cutter somewhere...

[Papalangi]

If it were flatter and not the only one left on the planet, I'd fire up the laser and have it cut in 3 minutes with a precision of .005".  Only problem is, although the hole would be the exact size needed, it's location would probably be a smidgen off.  Matching existing things like the cutout in the plastic are nearly impossible.

Michael

[Squiggle Dog]

If it were flatter and not the only one left on the planet, I'd fire up the laser and have it cut in 3 minutes with a precision of .005".  Only problem is, although the hole would be the exact size needed, it's location would probably be a smidgen off.  Matching existing things like the cutout in the plastic are nearly impossible.

Michael

Yeah, that's another idea.

[Squiggle Dog]

Here's a picture of the wooden console piece that I will need to cut holes in.

I've installed the B-pillars but for now they are just for show (and safe from storage damage) until I install the wiring harness.

Also, you can see how bad my front seats were earlier today. The springs were flattened and the skins were torn. I took apart the front seat and replaced the lower pan, springs, and pads that I got for a few dollars at Pull-A-Part. They looked like they were brand new! I had a spare bottom seat skin that was in better shape than what the car came with.

I installed the W126 seat heaters in the seat. They didn't fit like they are meant to because the heat pads have seven strips and my seat has 6 pleats, but I got them to lay flat and they cover about the same area. When I have the money to get new seat skins I'll probably buy new heat pads.

I replaced the section of foam in the seat back where it was worn and then cut the edges of the torn vinyl skin a bit neater. I stuck another piece of vinyl behind it and will probably use a soldering iron to melt the edges together to join the patched piece to the skin itself. I also replaced the panel that holds the netting.

I put the seat back in the car and sat in it to find that my head was touching the roof! I adjusted the seat so it was lower and it's about right. The seat is now very comfortable and very firm. I now know what a brand new W116 seat feels like. I will do the same thing to the passenger seat. I plan on this getting me by until I can have new seat skins made for all seats.

[Big_Richard]

Here's a picture of the wooden console piece that I will need to cut holes in.

youd be better off keeping that peice and finding your self another.

wood trims like that with no option holes drilled are ultra rare and command a higher price than the ones with holes in them already.... 

[nathan]

I was just about to say that. Don't cut holes in ghat wood or Oscar will cry! Nice effort on the project!

[Squiggle Dog]

Find me a wooden console piece that has holes for heated seat switches but not for window switches and I shall spare this one.

[Necrosis]

Find me a wooden console piece that has holes for heated seat switches but not for window switches and I shall spare this one.

As Sean Connery said in League of Extraordinary Gentlemen

"The Game Is On"