the ..Volvo controller... starts the low side and then goes to the high side...cutting the low side off. this way the fan is running when going into high. i ran mine this way with a...15 amp...(switch on) relay... before i blew 75 amp fuses and burned up one fan (running low/high at the same time)... Jay (mavdog) did a good writeup on this...:Handshake ...Frank...
this might help: http://www.nastyz28.com/forum/showthread.php?t=200028 You can of course piece it together with relays, just need some sort of input for temperature. There are after market temp switches available, or use the BMW one from the above article. Unless you are building a comparator circuit, a standard temp sensor will only give you a current to temperature curve, not simply on or off at a specific temp. If your ECM is programmable, you can code it to provide outputs once certain temps are reached. More reading: http://mmb.maverick.to/showthread.php?t=43847&highlight=taurus http://mmb.maverick.to/showthread.php?t=68907&highlight=Escort+fan
Great info guys, thanks!! The LED just lets me know that the switch commanded the relay to close. Fan switches are the part I have the least faith in followed closely by lower volume electronics that were made as cheap as possible to lower the price and maximize profits.
The one poster in this thread, Thoroco, evidently makes and sells a fan controller. His controller uses relays wired in parallel which is not a good way to switch large currents. He also starts talking about how "the alternator pushes too much current into the relay". He obviously hasn't a clue about how electromechanical relays and alternators work.
Lets me know when the fan cycles on and off. REally I just know the power is being cycled to the fan. It wouldnt tell me if the fan had failed itself. Only tells me the electronics that run the relay are OK.
The temperature gauge will let you know if the fan is working. That, and the fact these big fans can be heard pretty easily.
Agreed. I must look at those guages every 15 seconds especially temp. Its habit. Cant hear my fan at all with car running. Exhaust is too loud. Can hear it no problem with engine off. I got home in the Mav last night adjusted my controller. I heard my fan cycle from my neighbors across the road. Neighbor thought I was nuts since she couldnt hear it. Wife told her its my mechanic ears. I hear stuff all the time the wife cant pick up on the vehicles. Turned the temp adj. back up a bit, working perfect now. I like it on a constant feed. Surprising how much the underhood temps jump after shut off. It cycles for a few seconds, once or twice. No big deal. Kind of sounds cool after shut off too. LOL.
That's scary! The alternative that I have been dabbling with was using a variable controller(like on a 2006-up Crown Vic) to control fan speed but that requires a Pulse Width Modulated control circuit that would vary with temperature and a switch circuit to turn it on for AC and a trusty manual override. I'm not an electronic engineer so building a reliable unit would probably be time prohibitive but I took one apart to see what the current capability was of the power transistors(or whatever they are) and they were rated at 80amps each and there were 3. Not sure if they were in parallel but I was suprised at the rating. The PCM controls it on the Vic in response to engine coolant temperature and AC pressure inputs and it has a smooth slow ramp up to prevent the current surge when starting the motor. Maybe one of you electronics guys can come up with something because those fans are readily available too. These are used on police cars, regular CV's, Grand Marquis', and Town Cars and have been very reliable considering their unique usage. Unfortunately they are huge and would require a custom shroud or mounting to fit in the Maverick/Comet chassis.
