75ZT Community

Hi
The heated seat switches appear to work (they warm up) with the feed from the seat earth and then to the earth point.
But the switch button does not illuminate. Tried feeding a direct from battery 50Amp line to the 'illumination' pin but the car then refuses to start. Does anyone where I am going wrong with trying to get the heated switches to light up when switched on?

The illumination pin is so that the switch glows ornage when the lights are on.

There is a little green LED (Light Emitting Diode) inside the switch that lights up when they are on.

As well as the big feed from the negative side of the heaters (Yellow I think), and the big ground wire (Black), there should be a smaller feed to the switch (Orange white from memory), fed from the same place as the feed to the positive side of the heaters. Finally there is the illumination pin which is only for backlighting, fed from the light switch (red/white)

I tried taking my feed for the orange white (12v) from the positive feed of the seat heaters, but the cars electrics sort of died. This feed was the towbar 50 amp live. Any alternative power suggestions?

That feed should be plenty big enough.

Did you have the engine running? The seats won't work if the voltage isn't high enough.

I assume yours is an early car where the towing feed is live because on later cars it isn't.

You may also have a low or dodgy battery?

Hi
I have solved this now.
I replaced the Mk1 switches for a Mk2. Also fed the switch from nearer to the seat. Green LED lights now work.
Interestingly, the seats are also a lot warmer. I had heard that 75 seats were not very warm, and I will agree with that having used the old switch. However, with the new switch it is comparable to my previous experiences with this sort of equipment - you do feel the warmth now a lot more.
I have also discovered that I had too much / wrong sort of grease on the battery terminals through my experiments - this will be a factor too. Also, I have a budget battery fitted, at the low end of what is needed for these cars - with the extra equipment fitted now, I will upgrade to a heavy duty one when budget permits.
Thanks for your input.
Now just have to put the car back together!

Beware of heated seats - the following is from a non car forum - SO BEWARE:

After that, I grew up and was in a steady, staid sort of a job. With the aid of an interest-free loan from my employer, I bought a Volvo 343. Deadly dull but it was suited to my purpose. It did have a lot of gadgets for those days and I remember the heated driver's seat very well because, after I sold it to some girl, she complained afterwards that the heat melted her knickers! Don't know what sort of knickers she wore but I loved that seat on cold mornings.

I don't think there's any difference in the Mk1 or Mk2 switches. Maybe the old ones are just faulty? However they are very sensitive to voltage as I metioned. That said, taking the feed from nearer the seat would make it worse, not better.

Anyhow, at the end of the day it's working, so well done.