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Old 05-01-2014, 10:07 AM   #14 (permalink)
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lower hose temp switch + brake light circuit

Originally Posted by brucepick View Post
I did an e-fan conversion on my rwd Volvo 240 with 2.3 liter engine. It seemed to help FE.

Toughest part was managing the fan switching. I too wanted to mimick the constant breeze of the belt fan without excessive operation of the e-fan. I ended up very happy with a relay link running off the brake light circuit. When not moving or when crawling in traffic, the fan runs on low speed.

I added a temp switch in the rad lower hose (return hose) which is set some 20 deg. F cooler than the engine thermostat. So if the water from radiator isn't sufficiently cool to support the engine, the fan comes on, high speed. I got the temp for that switch set nicely; it comes on for long highway upgrades in summer, or if I idle it without using the brake. Otherwise it rarely activates.

Why I didn't use an upper (hot) hose switch -
I tried various temp switches in the upper (hot) radiator hose before going to the lower hose solution. In the upper hose, all switches would come on at highway speeds because the water there was already hotter than it should be (because it needs cooling). When I tried an upper hose switch at a high enough temp so it wouldn't come on from normal highway cruising, it also didn't help much in idling situations (stayed off too long), due to being set for too high a temp. Eventually of course it would come on but the temp gauge was rising by that point - which is what I didn't want happening.
Bruckpick, what an awesome idea. Are you still using the same type of a system, and would this work with the regular fan? What kind of temp switch did you add to the lower return hose?
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