W126 Front seat heater no low setting

Hi, I have front and rear heated seats in my SEL.

The rears are working fine, you have low and high heat settings which are indicated by either 1 or 2 led's on the switch.

On the front though you can only select high or number 2. It automatically drops down to low after a preset amount of time but you cannot manually select low, you push the button but the led doesn't come on and no heat appears.

Any thoughts?

Cheers
Matt.