Best place for efan thermoswitch

[JustJeff]

I'm doing a taurus efan with a 200 degree on switch I bought from Summit Racing.

I'm getting conflicting info about the best place for my efans thermoswitch. The thread of the switch matches a closed port on the bottom driver side of my koyorad.

My thinking is that bottom of the radiator is going to be where it's the coolest. Friend advised NOT to use that bottom port for the fan switch because of that. However the machine shop says the bottom of the radiator will be same temp as the engine.

Based on the machine shops advice I left it with them to open the that bottom port. Is this sound advice? Should I call the shop and tell them NOT to open the port?

[FerociousP]

It will be cooler... how much, I don't know.

I used the thermoswitch location on the back of the waterpump using a NPT adapter for my gauge. It isn't the ECU temp sensor. Mine is s5 turbo, so I don't know if your specific model has it or not.

FYI it is a one pin sensor and goes to ground at 207*, which you might find suitable (normal operating temp is 185-195ish)

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=10045&d=1300999479

[FC Zach]

I'm using one of the holes at the water pump housing.

[KTune]

I use a 190 degree switch placed in the thermostat housing to control my fan. Has never caused any issues.

[JustJeff]

It will be cooler... how much, I don't know.

I used the thermoswitch location on the back of the waterpump using a NPT adapter for my gauge. It isn't the ECU temp sensor. Mine is s5 turbo, so I don't know if your specific model has it or not.

FYI it is a one pin sensor and goes to ground at 207*, which you might find suitable (normal operating temp is 185-195ish)

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=10045&d=1300999479

I thought the same type thing and was just looking at that page to find when it switched.

My question is I want to keep my A/C. Am I correct that the OEM purpose of that switch is for an a/c efan and also to bump up the idle when the a/c is on? Can I simply splice into that wiring, use a relay to switch polarity and have that sensor do it's OEM purpose and kick on my efan?

My other question is that my Summit switch matches the diameter of the OEM switch but the threading is different. What about retapping that spot for the Summit switch and using the 200 deg switch to do both OEM and radiator efan? Can I use a relay to switch polarity to ground and have to go to my engine harness then also have the signal go out as intended to kick on my efan?

If everythign else in my post is correct and possible won't that have my idle kick up anytime either the efan or the a/c come on and also turn on the efan???

[Mazdabater]

Do you have an aftermarket ECU? Most ecu's have an output for one

[TitaniumTT]

WP housing, pre t-stat. Bottom of the rad is going to be the coolest. You're trying to regulate the temp of the engine, not the temp of your rad, so why would you want to get a temp reading in the rad?

[Buggy]

Either somewhere in the water pump housing or right in the top of the thermostat housing is the best spot for it. That is where the coolant is the hottest just before it goes to the radiator. On my S4 NA the thermostat housing had a spot on it for the factory thermo switch that wasn't drilled or tapped. I installed my switch there. My TII has a factory electric fan and that is where Mazda installed the switch for it.

[FerociousP]

I thought the same type thing and was just looking at that page to find when it switched.

My question is I want to keep my A/C. Am I correct that the OEM purpose of that switch is for an a/c efan and also to bump up the idle when the a/c is on? Can I simply splice into that wiring, use a relay to switch polarity and have that sensor do it's OEM purpose and kick on my efan?

My other question is that my Summit switch matches the diameter of the OEM switch but the threading is different. What about retapping that spot for the Summit switch and using the 200 deg switch to do both OEM and radiator efan? Can I use a relay to switch polarity to ground and have to go to my engine harness then also have the signal go out as intended to kick on my efan?

If everythign else in my post is correct and possible won't that have my idle kick up anytime either the efan or the a/c come on and also turn on the efan???

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.

http://rotarycarclub.com/rotary_forum/attachment.php?attachmentid=10046&stc=1&d=1301061639

I used this adapter kit (10.99) to mount my gauge there. I believe its M16 or M14, which isn't NPT thread and required me to use an o-ring (same size as thermoswitch) to seal it.
http://prosportgauges.com/metric-adaptor-kit.aspx
http://prosportgauges.com/images/products/display/Metricadaptorkit.jpg

[Pete_89T2]

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]

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]

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.

[JustJeff]

Thanks for all the feedback.

TTT-you're right and it was my same belief before going in the machine shop. The machinest convinced me that the radiator would match temps of the engine. Fortunately I caught them before they opened up the bottom port on my koyo.

What I'm thinking is swapping the OEM thermoswitch for my Summit Racing. Splitting off the signal from that. One going to the engine harness and the other going to a relay to control the taurus efan.

I like the idea of tapping into the factory wiring for the relay, but I'm also concerned about the draw the Ford fan creates. On high the fan can practically lift off the ground.

[FerociousP]

Thanks for all the feedback.

TTT-you're right and it was my same belief before going in the machine shop. The machinest convinced me that the radiator would match temps of the engine. Fortunately I caught them before they opened up the bottom port on my koyo.

What I'm thinking is swapping the OEM thermoswitch for my Summit Racing. Splitting off the signal from that. One going to the engine harness and the other going to a relay to control the taurus efan.

I like the idea of tapping into the factory wiring for the relay, but I'm also concerned about the draw the Ford fan creates. On high the fan can practically lift off the ground.

No need to "split" the signal... just replace the relay in the picture with one of your choosing the wire that you fell will handle the amperage.... done and done. If it runs too hot for your liking, replace the switch.

[JustJeff]

Update:

I didn't like the idea of tapping the OEM switch spot for the Summit switch. I was afraid I'd run into leaks and because the switch gets ground from the mounting I was afraid to use teflon tape to help seal it.

I ordered a Starion fan switch from a local parts store and it will arrive sometime this week. Starion switch is on at 195 and matches the M16x1.5 thread of the OEM spot.

With that decided I can now have engine parts powdercoated!!