96 300tdi usual problems!

Hi,
I have been lurking a while and using the forum for searching to get the answers but have come across an issue that's not fully explained.

My crash sensor (dreaded green box) has become overly sensitive. Some days it is fine but others it will trigger when going over a pebble causing the clicking noise and the hazards to come on. When it happens I pull over and pull the fuse out for the indicators as no matter how many times I turn off and on it won't completely cure it.
I really don't want to have to go to the expense of getting a new one and having it coded to a new fob.

Will fitting a spider by pass cure this particular problem? I have no issues with it starting.
If not, what's the options?

I have the centre dash apart at the minute as my heater has been playing up, would only work on 4 and now won't work at all. I noticed that the relay (first one you come to by the accelerator in the footwell) doesn't click when the ignition comes on. I intend on replacing it but can't find the correct one on eBay, anyone got a link?
If this doesn't work then the next option is a new switch.

Wrap the green box in bubble wrap and stuff it back in but I think it's on it's way out so will need replacing,also a spider won't do anything apart from bypassing the immobiliser.

The inertia switch ( crash sensor) is a separate circuit and part of the security ecu. (green box) removing the spider has no effect on that that sensor. The sensor can be come over sensitive and normally switching off and on the starter switch will reset, if that's not happening then you have a problem with the security ecu. Check its securely fix to the bracket.
With the heater fan speed it's usually that the resistor positioned on the heater box is faulty, most or the relays have a number on them, ie YWB10027L you will find a few of themin the RH footwell.

Lovely thanks.

Resistor on the heater box? Where would I find that?

Google STC3133 it's the resistor pack for D1s from VIN 081992

Right,
Got a new resistor and fitted it. No change.

I was driving the other day and turned the blower speed to 4 and noticed a burning smell. When I pulled over I touched the connector for the blower speed and its red hot.
So I changed the whole switch panel and nothing has changed. The connector for the blower speed with still gets red hot when I turn it to 4. The fan doesn't come on.

What could that be?
If it is an earth wire blown then what colour is that?