Ford Focus 2003, 1.8 TDCI power issues

[Newbs]

Hi,

I've been having this issue for a while, and its getting on my nerves again now we are in the winter! Basically, the following happens:

1) Turn the car on

2) Put on front heater (electric, not fan)

3) The power light comes on, and the heater goes off.

The *only* way I've found to then turn that light off is a full power down of the car, and re-starting it. I've had the following done:

1) New alternator last year

2) New calcium battery (as recommended)

3) I've even had the front window replaced, due to half of the screen not working (the whole screen now works, but thats assuming that battery keeps up! haha)

I've been doing a ton of reading online, and one thing that keeps coming up, is the "smart charge". Someone suggested checking the fuse... but I wouldn't even know where that is? (I've checked the diagrams, and no mention of it). Someone also suggested cleaning the "smart charge plug" , but I'm not exactly sure what that is either :) I really don't want to have to take it to the mechanics, as I've already had to spend out a couple of grand out on it this year .

Thanks for any suggestions

Andy