OK, here it is...
There is a control unit under the passenger seat. This monitors electrical load. When the load reached a certain threshold, control unit opens the solenoid on the carburettor.
Here’s some tests
inspect the solenoid wiring
Inspect the connections to the control unit under the passenger seat
Check the fuse to this is good. (In my book its the right most fuse in the fuse box under the dash drivers' side. 15 Amp, Yours might be in a different place though, so if in doubt check them all. Check if this fuse is even there....)
Unplug the solenoid wiring and connect a volt metre across the wiring harness. All electrics off...start engine...turn the rear window heater or headlights on and off...check that the voltage changes between 0v (ish) and 12 V (ish) on the volt metre.
To check if the solenoid works....disconnect and reconnect the battery negative lead (be aware of loosing your stereo security code and clock etc). Listen close to the carburettor...you should hear the solenoid clicking as the battery lead is connected and disconnected. You might benefit from the use of an enthusiastic volunteer!
Testing the control unit is fiddly so assume its working for now....come back to it if all else fails.
Let me know how you get on
Rich
