strong electrical burning smell behind dash.

Cig lighter is always a suspect - generally has a big fuse and after time they can cause shorts as there’s a live feed usually mm from a good earth. They’re sometimes only screwed together and a bit of wobble is all that’s needed to make the contacts touch when they shouldn’t.

I had something similar recently with a dimmer and non-functioning dash lights. I'd have a look to see there isn't a fault in that circuit causing the resistor to get hot?

Is the blower motor still working? They tend to smell/chances of smoke when they seize...

Capri heater motor switch, centre off, one speed up, two speed down or maybe the other way up but definitely centre off.
Dimmer resistors are pants, not designed to carry much wattage so if one of the instrument lights is shorted the resistor will burn out, this would also cause all the bulbs to 'not work' as the electricity takes the path of least resistance to earth.

To test for 'short to earth' use a continuity tester with it's own battery or a multimeter to avoid further possible damage.

First test the obvious, remove battery and test pos to neg making sure all switches are set to off position. If the car is fitted with a clock in the centre console, disconnect it.

If there is continuity, if the lamp lights or the meter beeps, then move the fuse box, pull all the fuses and check the input side, then output side, of each fuse holder. (input side will test positive across some of the fuses, output side should not.)

Connect one side of the continuity tester to body earth. Check the output side of the fusebox to see if any of them cause the lamp to light. Assuming one of them does cause the lamp to light find out what that fuse provides power to and if it cross connects to any of the other fuse holders on the output side.

Mark any plugs you disconnect under the dash so you know where to plug them back in. Tape up any loose connectors or wire ends.

Fords used a common basic wiring convention. I think brown with a red tracer is an earth wire that should only carry current when the IGN position is used on the key, brown with a yellow tracer carries current when the ACC position is selected. Thats from practical experience re-wiring kit cars based on old escorts so if someone could verify that it'd be useful.

Having had two major re-wires due to 'little mishaps' under the bonnet or dash of my kits please avoid putting the battery back on until you find the fault, it's a lot harder to put out a fire in these old wiring looms than the new thin wall wire looms.

I had a quick go at this while i was working on the steering rack (i forgot about disconnecting the interior clock though) . I didn't get any "beeps" from my multi meter when touching the battery terminals and the fuse terminals (fuses removed). I tested both sides of the terminals to the front wing. I'll try this all again next week when i have time and energy.

I'm starting wonder if it was the heater fan with the heater switch being in the down position. If i was to take this out, could i connect the unit or just the motor to a 12v score or would it be stepped down from 12v in the car? I thought for piece of mind this might be the easiest process of elimination.

I noticed another crude electrical tape up today under the bonnet... what i'm guessing is a electronic ignition module seems to have a gaffa taped wire loose. Not sure if it is something left over from a conversion (looks like a ford part) but will need to go scouting for this kind of stuff. Cant remember if i mentioned before but there are two extra terminals attached to the positive side of the battery... i cant see any extras on the car though.

Cheers this is all great advice as electricity is a dark art to me. Maybe i'll just unplug the heater switch multi plug even if seems ok for now. Will check the dimmer control and i'm going to add something to the cig lighter to take up the load. Is the cig lighter the only thing that will miss having a load wired up to it?

From what i've seen on this wiring diagram it looks like the Glovebox light, heater, cig lighter, dashboard dials/dimmer are all on this one fuse!! i'm assuming this is the same for my Car and it looks like non of these things work properly which is a bit worrying. The fuses them selfs seem fine as i checked them today and cleaned up the contacts (no fuse cover box   )

the heater motor has probably seized - its inside the black plastic box under the dash/above the transmission tunnel. You can get replacements - trying to open up the heater box without snapping plastic clips is the most difficult thing. Mine is held together with quite a lot of cable tie!

I had issues with my headlights when I first got my capri and loads of weird wiring which I ended up stripping out. There is another silver/grey fuse box on the other side of the engine back which has the fuses for the lights - worth giving those a cleanup as well...

I've also got one of those quick disconnect things on my battery, although it fits straight on the terminal. Think it was only a couple of quid off eBay...and no chopping needed.

Not a best picture - but you see the grey box on the passenger side bulkhead? That had the headlight fuses: