since i got my current 5 the antiperculation fan seems to run a lot of the time when it isnt realy needed, this seems to be draining the battery and whilst it still starts fine i cant see it being good for battery life or the life of the antiperc fan.

looking at the haynes manual the first thing that occurs is that the diagram must be wrong as it only shows one thermal switch so moving on i had a look at how it was wired on the car and it appears that the thermal switch on the carb is connected in parallel with the one on the turbo heatshield however when driving the one on the turbo heatshield spends most of its time on and i wasnt sure it realy needed to be on all the time so i disconnected it to see what effect it had.

my observations were that the antiperc fan ran a lot less, only coming on by the thermal switch on the carb when i was edging along in traffic on a particularly hot day and then only for around 60 seconds at a time, i didnt feel any effects of fuel evaporation whilst driving, the only downside was needing to crank it more to start as fuel evaporation had occured after the engine was turned off.

my thinking now is that i could use a relay to dissconnect the thermal switch on the turbo heatshield whilst the ignition is on so that it wont keep the antiperc fan running whilst driving and allow the carb thermal switch to control the temperature of the carb whilst driving.

then when engine is shut off the relay would allow the thermal switch on the turbo heatshield to keep the antiperc fan on until engine bay temperatures come down solving the fuel evaporation after shut off

anyone have any thoughts on this ??