Join Date: Jun 2002
Location: Melbourne's West
Re: wiring thermo fans, help???
Couple of points here.
Coil uses a sneaky system that switches 12V to the coil for starting, then switching in a really long length of resistance wire to drop voltage to about 7V once the engine is started. Otherwise coil burns out. So if you hook your thermos up to the coil, they will run slower (7V instead of 12) but they are pulling a huge amount of current through a tiny diameter wire only meant to run the coil. Not good for reliability.
Hooking the thermos straight up to the fusebox is also a problem - heaps of current through a box not designed to take it. You run the risk of smoking your under dash wiring, and possibly setting the whole car on fire (once you get a fire going under there it is bloody hard to put out). Remember, these cars never came out with thermo fans! Use a relay to switch power from the battery. and use in-line fuses to the fans to save embarrassing smoke from your wiring loom if the fan(s) shorts.
Now the best thing is to use a thermo switch to control the relay to switch the fans on and off - you don't want them running when engine is cold, only enough to keep it at a good operating temperature. Engine runs more efficiently, and a LOT less load on your electrics. As stated, there are a lot of threads on the subject showing you how to hook them up.