I had an LED on mine to show when the high speed turned on. Wired right to the high speed relay contacts. What I found was the LED was bright when the fan turned on high and dimmer when the fan turned on low.
that's where I was at with wanting a sensor to detect the fan blades spinning but would need a brake for the fan when off.
I was going to use 3 colors. I have a switch in the relay ground that I use to turn the fan off. I would run a 12v through one LED that would ground when the fan switch is on. This would help me remember to turn it on. One led for low powered by the low speed power, and another one powered by the high speed fan power. This would give me some extra feedback on what engine temp is doing along with a gauge. I have a '74, and I was thinking of tracing out the wires for the seatbelt system bypass button under the hood, and use those wires to run my l.e.d. s.....or just run some more wire, but it could be less cluttered if I use the harness already there as long as it doesnt invite some sort of trouble. I am going to put in a temp gauge and all the LEDs would be next to it. I can feel the warm air the fan pushes out at a stop by putting my hand out the window.....it is a manual fan tester.
When I installed it, the temp. sensor was put in the T-stat housing. I assumed (there is that word again, lol) that cooling the radiator after turning the motor off would just draw a lot of juice and do nothing for a hot engine since the water pump would be doing nothing. The BMW I took the temp switch from had it in the radiator....which I can see how it would turn itself off. Is there any level of desirable cooling that can happen after the water pump is off? I am running a 160* t-stat, so the running temp is somewhat low.
When our Mav/Comets or for that matter, most cars back then came out, no electric fan, engine off, fan off............. David
Stu, I have my electric fan running with engine off to allow continued airflow through the radiator and under hood area while waiting in the staging lanes. When time allows I just open the hood. Also there is the slick factor; with the fan running and hood closed my Comet sounds like an older Honda or Toyota Other than that, I don't believe there is much value.
I just have my fan wired directly to the battery through a circuit breaker. When the engine is turned off it'll cycle on and off a couple times on low speed and cool things down. Even though the water pump isn't running heated water still rises slowly in the engine by convection. My temperature switch is located in the upper radiator hose just before the radiator. Once the water cools enough that the thermostat doesn't open the fan stays off.
Lol....I havent been to through the staging lanes yet, but I think the ol junk motor has got a 13.xx pass in it if I dont waste too much time spinning my lone tire. I want to get my LEDs up to make the Hondas jealous though.
