1997 Z3 2.8 heated seats wiring help

[chuck kamas]

Hi all,

I finally had my leather seats recovered. They look great. However... there is always a however, the heated seat wiring came back disconnected. It looks like the wiring to the seat bottom pad is OK, but the wiring to the backrest pad is partially broken. I say partially, because from the black connector, the wiring splits into one set heading the the backrest heater and another heads to a green connector to a set of red wires that got cut! I can not find where these wire are supposed to go. Does any one have pictures of the under side of the seats showing where this wire goes?

Cheers!

 

[Mazza]

Hi and welcome to the forum.

The colours on your wiring don't seem to tie up with the circuit diagram ????

Usually its two brown earth leads and two white with coloured stripe leads to each connector.

Are they after market additions????

I dont know if these will help you sort it

This is a wiring guide info sheet, which may help

 

[Mint]

If they came back cut, can't you go back to where you had them recovered. If they cut them they should repair the damage.

 

[Mario]

Coming to the rescue - the mystery end of Y can only be two things either the connector from a sensor that goes on the back of the seats and stops them from pushing back once the seat back makes contact with the firewall or a temp sensor that cuts the heating if the heat is too hot - the mystery cable split is definitely where the temp sensor goes - tip - if you measure the seat heating plug with a multimeter pins one and two resistance it shoould be about 5 ohms - then resistance on pins 3 and 4 should be also about 5 ohm - if you measure resistance on the pins that have the mistery Y attached and get no resistance measurement (open circuit) you've found your problem.

 

[chuck kamas]

Thanks, I will look for a switch / temp limiting circuit still in the back rest...

I'll let you all know if I make progress!

Thanks

I've look and can not find any evidence of a safety switch in the seat back. Does anyone have a photo of this area on the bottom of their heated seat?

Thanks

 

[Mario]

The safety switch on the sport seats goes under the plastic back cover then the cables run down the side on the back then to the bottom I believe regular non sport seats don't have this.

 

[chuck kamas]

So I took the leather off... Lots of Hog Rings to be installed in my future! I looked at the back rest and did not find any switches. Nor did I find any broken wires. I am at a loss again!

above stripped seat back

Above where the wires that are connected hook up to the heating pad on the seat back

above the seat back heating wires

stripped seat back

above seat bottom with mystery wiring in series

where the wires connect to the seat bottom heating pad

the mystery wire!

 

[the Nefyn cat]

The horrible hog rings can be replaced by cable ties, makes life a lot easier.

 

[Mario]

Did you do the continuity check on the pins to measure resistance

 

[chuck kamas]

Thanks for the advice on the cable ties... how do they do long term with the heated seats?

Regarding testing the heater pad resistance. Since the mystery wires are in series, if I short them together then yes I get resistance of about 4-5 ohms. So something switch like must have gone here. Curious!

 

[Mario]

Then somehow the temperature safety switch has disappeared no big deal you can short those pins and the seat heating will work no problem I guess if you have your pants on fire because they overheat you will realise pretty quick lol

 

[chuck kamas]

you are correct, and that is the approach I will take, just soldering the wires together.

However, I am enjoying the exercise in curiosity. Why is this switch included and where did it get installed? Why can I find no mention of it in the tech manuals?

 

[Mazza]

Just had a thought.......Your car isn't one of the Limited Edition 007 James Bond cars is it????

If it is, that could be the wiring for the ejector seat. .............

 

[the Nefyn cat]

Just had a thought.......Your car isn't one of the Limited Edition 007 James Bond cars is it????

If it is, that could be the wiring for the ejector seat. .............

Probably best not to tamper, then.

Thanks for the advice on the cable ties... how do they do long term with the heated seats?

Only had them in a couple of months, after fitting some carbon-fibre mesh type heater pads, no problems so far. I remember the hassle I had last time I fixed the heating and re-used the original rings, soldered a bit of wire in to replace the burnt bit, lasted a few years. If you go the cable-tie route, make sure you fit them so they're easy to get to when you pull them up tight, got them the wrong way round the first time and had to start again.

 

[Mario]

I think it goes on the seat bottom part and I have seen many heated seats without them safety sensors, probably started installing them later in the production run once some American started suing them because he burnt his ass with the seat

 

[the Nefyn cat]

Mine got uncomfortably hot just before it burnt out the second time, and there didn't seem to be any sensors in there when I stripped it, just two wires that split and head off to the base and back.

 

[chuck kamas]

Hummm... I could install ejector seats! Now that is something to look into!

 

[the Nefyn cat]

Now, I can't remember what the MOT book said about ejector seats. I guess if they're fitted they have to work.

 

[chuck kamas]

I think that I might have figured out WHERE the heater over heat safety switch was located... Just not sure what was there!

There is a hole in the front of the seat bottom the would accommodate a safety switch....

And a hole in the foam of the seat at that location.... but no evidence of a switch....

My curiosity will kill me.

 

[the Nefyn cat]

Could (perhaps) be for a pressure switch for an aftermarket alarm? Definitely nothing like that on mine, but they do vary with age.