Best place for efan thermoswitch

Pete_89T2 · 03-25-2011, 10:03 AM

Quote:

Originally Posted by FerociousP

If that sensor is there, then you probably have the relay (or at least the wiring for the relay) that switches that fan on. Do you have the little fan on the front of your condensor? You can just use its wiring. You already have the FSM, but I'll post it for the others. To me it looks like the A/C control unit grounds the relay just like the switch does. I believe the idle control has nothing to do with this part of the circuit.

That's correct -the stock ECU (S5 T2 at least) uses the A/C switch to trigger the increase in idle speed. That's independent of the water temps. But I would caution using the existing auxillary e-fan wiring as-is to directly drive the Taurus e-fan, as that sucker will draw much more current than the stock aux. fan. What you could do is use the wiring up to the aux e-fan motor, and instead of having it power the motor, use it to energize a relay, which would in turn switch a circuit sized accordingly to supply current for your Taurus e-fan. At that point you can chuck the stock aux. e-fan as the Taurus fan will be doing its job, and handle regular cooling needs, provided you swap out the stock temp switch for the Summit one that trips at the lower temperature as you suggested a few posts ago. If it were me though, I'd look for a switch that trips below 200*, like 185~195*F.

FerociousP · 03-25-2011, 01:19 PM

Quote:

Originally Posted by Pete_89T2

That's correct -the stock ECU (S5 T2 at least) uses the A/C switch to trigger the increase in idle speed. That's independent of the water temps. But I would caution using the existing auxillary e-fan wiring as-is to directly drive the Taurus e-fan, as that sucker will draw much more current than the stock aux. fan. What you could do is use the wiring up to the aux e-fan motor, and instead of having it power the motor, use it to energize a relay, which would in turn switch a circuit sized accordingly to supply current for your Taurus e-fan. At that point you can chuck the stock aux. e-fan as the Taurus fan will be doing its job, and handle regular cooling needs, provided you swap out the stock temp switch for the Summit one that trips at the lower temperature as you suggested a few posts ago. If it were me though, I'd look for a switch that trips below 200*, like 185~195*F.

Well, that would be using a relay to switch a relay... but whatever. And also, notice in the FSM that the thermostat doesn't even fully open until 203*. If normal operating temp is 190-195, then the fan would come on while you were driving down the road, which you don't want to happen. As long as the connections are in good shape I'd imagine the wiring to be satisfactory.

But... if the switch isn't even there then this all doesn't matter. Just trying to make the mod as simple as possible. FWIW, I still use the fan clutch on my current T2 and have had zero cooling issues. Is the minimal parasitic loss worth the hassle?? Not to me.

Pete_89T2 · 03-25-2011, 02:23 PM

Quote:

Originally Posted by FerociousP

Well, that would be using a relay to switch a relay... but whatever. And also, notice in the FSM that the thermostat doesn't even fully open until 203*. If normal operating temp is 190-195, then the fan would come on while you were driving down the road, which you don't want to happen. As long as the connections are in good shape I'd imagine the wiring to be satisfactory.

But... if the switch isn't even there then this all doesn't matter. Just trying to make the mod as simple as possible. FWIW, I still use the fan clutch on my current T2 and have had zero cooling issues. Is the minimal parasitic loss worth the hassle?? Not to me.

Yeah, that would be using a relay to switch another relay, but my concern is that the current draw of the Taurus e-fan is most likely much more than that of the puny stock aux. e-fan. That plus the fact that the stock e-fan wiring is over 20 years old means you might might burn up the wiring if you ran it direct. Now if we had some test numbers to compare the current draws on both fans, we could determine if the stock wiring is sufficient as-is.

WRT the switch temp, you're right that dropping below 200* would result in running the e-fan too much while you're moving, but that extra safety margin helps for times when the car is stopped dead idling, i.e., if you're running hard on the freeway and you suddenly find yourself stuck in a traffic jam. Kicking the fan on at a lower temp helps postpone the inevitable heatsoak condition.

I agree on the stock clutch fan, that's what I'm still using too. Even when I had my stock radiator, I rarely saw water temps go above 205*. I recently put in a Koyo N-flow radiator, and the same setup has kept me below 180*, but I haven't driven in hot weather yet.