[Ruslow]

OK I have read on what to do and triple checked everything,pin 41 is suppose to be gnd for the relay but it is not gnding! lowed the temp setting to 110 on both hi and low speed fan in the calc and yes I have the fan scalar on so it should work.do some of the GUF strats not have this function?Stan

[decipha]

it has been speculated that some of the fox ecu's cannot control a fan at all

heres the write up with details http://info.efidynotuning.com/foxfan.htm

be sure you have all the tune changes needed

[RJCarp2]

I asked this question in the hardware section, but since this thread is recent, I'll ask it here too: do the fans run with the key on, engine off assuming that ECT is above the setpoint? I'd like to test the fan function by lowering the setpoint below my garage temp and checking that the fans turn on while the key is on and engine is off. It's a brand new motor and all new/custom wiring transplanted in a '65 Mustang and I'd like to know the fans are going to work when I start this thing up.

Thanks,
Rich

[xd41efisc]

The engine needs to be running from memory.

[harold]

Right, the engine needs to be running. I spent too much time trying to figure out what I'd done wrong because the fan relay wouldn't trip no matter what I did with the engine off. Fired up the engine and I could toggle the fan by changing settings in the tune and updating.

[RJCarp2]

Thanks guys. That saves me some time.

[Shaker666]

FYI, all GUFB EEC-IV units can control dual independent cooling fans. Since 71001 chip is not widely available anymore, you can use TI DS3658N in its place (direct drop in replacement) and a diode.

The high speed fan output from the EEC-IV is a grounding type, so its output can be used to directly ground the field coil of a relay, but the low speed fan output is inverted to provide fault tolerant fan operation. Therefore, it requires an NPN transistor to operate a relay. I used a TIP31 transistor and a voltage divider to pull things down to 5ish volts to invert the low speed fan output. With this setup you'll be able to set both your high and low speed setpoints in your tune and watch them function perfectly.