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Discussion Starter · #1 · (Edited)
For a 1994 GL with 3.8 engine: With the coming of summer, I'm working on installing something to run the radiator cooling fan more often, due to some problems with my transmission that make it work better when it's not too hot (which I'll be fixing soon once I learn how). I may install a transmission cooler too. From what I understand, normally turning on the air conditioning will turn on the radiator fan, but not in my Taurus--neither at Normal or Max A/C, maybe because I don't have an A/C compressor and clutch installed. Both seized up last year, and I just removed them and installed a bypass pulley until I get around to installing replacements. So, there's no clutch to plug its electrical connector into, and I'm guessing the computer wants to see that circuit close, or something indicating the compressor and/or clutch are there, before it will turn on the radiator fan when the dash switch is turned to A/C. My radiator fan starts up normally whenever the engine temp on the dash gauge goes a little past midline, so that circuitry is working.

So for now, I'm looking at adding wiring to apply 12 volts to the CCRM's pin 14, to activate the low speed fan relay inside the CCRM. I'd prefer the 12 volts to be from a point where power from the alternator is active only when the engine is running (hot at run) (any advice on what's a good point for this?), instead of directly from the battery, because I don't want the battery to run down if the fan is left on while the engine isn't running. Also, I'll be putting a one or two amp fuse in the wire to be safe. I haven't decided whether to:

• install a wire from the 12 volt source, to a switch I'd add on the dash, and then to the CCRM, to allow me to turn the fan on and off manually;

• go without the switch, and just connect a wire from the 12 volt source to the CCRM, so the fan is on whenever the engine is on;

• mount a thermoswitch at a location I'd use as a temperature reference (maybe attach it directly to the metal cooling line coming out of the transmission), and place the thermoswitch in-line between the 12 volt source and the CCRM, so that the fan comes on only when the ATF heats up to whatever temp the thermoswitch I choose is designed for. This was inspired by a sub-topic in egiroux's classic thread at http://www.taurusclub.com/forum/82-maintenance-repair/156770-if-has-come-out.html.

Does anyone have ideas on which approach might be best, or possible downsides to any of these approaches? And what's a good point from which to tap off for the hot-at-run 12 volts?

I tested the basic operation of this setup, by back-probing into pin 14 on the CCRM's connector with a metal paper clip, then connecting an alligator clip lead to the paper clip, then to a fuse, and then I touched the other leg of the fuse to the battery's +12 volt terminal, and this turned on the fan in low-speed mode just fine, cooling the engine pretty dramatically in just a few minutes, from above midline on the dash temp gauge, to nearly down to the bottom of the gauge. When I first manually applied 12 volts (which was actually about 14.5 volts due to the alternator's contribution) to CCRM pin 14, I was worried I was shorting something that shouldn't be shorted, because there was a spark at the point where I touched the fuse to the battery, and for the first two or three seconds, the hood light dimmed a little and the alternator slowed down a little, but then I realized this was just the effect of the extra load of the fan, and both returned to normal quickly as I kept the connection closed, as the alternator compensated for the extra load.

I also made some measurements with the extra wiring disconnected, and with the engine running until it got hot:

• Switching A/C on, to either Normal or Max, didn't result in voltage rising above zero at CCRM pin 14.

• When the engine temp got hot, the fan started up as normal, and voltage at CCRM pin 14 rose to 14 volts.

• Voltage at CCRM pin 17, the high speed fan circuit, always showed 14 volts. Another thread here says activating the high speed fan circuit manually can cause unspecified trouble, so I won't try to do that (even if I knew how), and the speed of the fan at "low speed" seems pretty good to me.
 

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Just add the transmission cooler, in line with the original cooler, and that will be enough. The thermoswitch idea sounds good but it may be difficult to install.
 

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I wouldn't bother with a switch to be honest. You wont gain anything by installing the switch. the car knows when to come on and it is only useful while idling. Also you would need to remember when to turn it off and on.

Also running too cold can also be detrimental on performance just as well.

If you really want to run cooler I would go for a dual core radiator or a lower temp t-state. Both will allow you to run cooler and will be good at more then just idling. You can also try Redline Water Wetter. It helps to reduce water temperatures.

We have the products here: Engine- Cooling - SHO Source
 

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I wouldn't bother with a switch to be honest. You wont gain anything by installing the switch. the car knows when to come on and it is only useful while idling. Also you would need to remember when to turn it off and on.

Also running too cold can also be detrimental on performance just as well.

If you really want to run cooler I would go for a dual core radiator or a lower temp t-state. Both will allow you to run cooler and will be good at more then just idling. You can also try Redline Water Wetter. It helps to reduce water temperatures.

We have the products here: Engine- Cooling - SHO Source
I disagree! The PCM wants to maintain the Engine temperature (210 F or so). This allows the hot coolant to get to the discharge side of the radiator where the original cooler is. In other words, much of the time you will be heating the tranny fluid if there is no air flow (stop and go traffic). The switch in the tranny cooler line prevents this.
 

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If you want a fan on the trans cooler, B&M makes a trans cooler with the fan and t-stat turn on built in. all it needs is 12v.

Let the PCM manage the motor temp.
 

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If you want a fan on the trans cooler, B&M makes a trans cooler with the fan and t-stat turn on built in. all it needs is 12v.

Let the PCM manage the motor temp.
This is true, but it costs about $250 IIRC. The switch was about $6 for 5 of them.
 

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Run the factory thermostat, I agree with egiroux. The low temperature thermostat will actually decrease fuel economy and create more carbon buildup due to incomplete combustion. Also the wider variance between then thermostat opening and the preset fan temperature creates more stress on gasket materials, ie too much hot/cold cycling.
 

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Discussion Starter · #12 ·
Thanks for the input!

If you want a fan on the trans cooler, B&M makes a trans cooler with the fan and t-stat turn on built in. all it needs is 12v.

Let the PCM manage the motor temp.
I didn't think of this. It sounds like the best way to go--separate hardware controlling transmission and engine temp. Even if both work best at about the same temp, the stock radiator fan, engine coolant temp sensor, and a regular auxiliary ATF cooler, might not keep both at that temp; and from what I think I understand, the engine can take (and can run better?) at higher temps than the transmission. $250 is a bit much for a cooler, but might be worth it, even if it extends the life and improves the performance of the transmission only somewhat better than the other approaches.

The PCM wants to maintain the Engine temperature (210 F or so). This allows the hot coolant to get to the discharge side of the radiator where the original cooler is. In other words, much of the time you will be heating the tranny fluid if there is no air flow (stop and go traffic).
This is one of the things I'm concerned about. Sometimes in Sacramento-area traffic jams, I have to idle longer than I want during the summer (often over 100 F), so more control over ATF temp would be desirable for that.

I wouldn't bother with a switch to be honest….the car knows when to come on and it is only useful while idling.

If you really want to run cooler I would go for a dual core radiator or a lower temp t-state. Both will allow you to run cooler and will be good at more then just idling. You can also try Redline Water Wetter. It helps to reduce water temperatures.
I'm not sure I can rely on the computer's reading of the engine coolant temp sensor to start the fan on time (though is the ATF temp sensor involved in starting the fan too?) for the current shape my transmission is in, since for the past few months, it's been shifting better (faster, less apparent "strain") before the ATF heats up substantially, and once the ATF heats up and the shifting quality diminishes, it doesn't improve as much as I'd like after the fan kicks in. What the computer considers the right engine temp to start the fan, is past the temp my transmission currently likes to work well.

I may try your suggestions for separate control over engine temp if that becomes an issue this summer. The engine only sometimes gets a little warmer than usual (at least after I fixed some coolant leaks a while back), going a little past its normal position of a little past midline--nothing to worry about at the moment. Unless the engine starts getting too hot too often this summer, it may be best, as suggested by crackhead and WJC, to let the computer use the reading from the engine coolant temp sensor to handle engine cooling via the radiator fan.

Run the factory thermostat, I agree with egiroux. The low temperature thermostat will actually decrease fuel economy and create more carbon buildup due to incomplete combustion. Also the wider variance between the thermostat opening and the preset fan temperature creates more stress on gasket materials, ie too much hot/cold cycling.
Good points, thanks for pointing them out.

I'll probably do this: Both as an experiment (I like gathering data) and for practical purposes, I'll temporarily install a manual switch on the dash, so I can fiddle with it while driving to see if I can detect any improvement in shifting when I have control over ATF temp. This might give me more info than an always-on fan, and wouldn't cause the engine and transmission to stay too cool, and would be a little less work for now, than installing a thermoswitch or a cooler (only because I already have manual switches, but not a thermoswitch or cooler, so I could hold off for a while on picking and ordering new parts). After experimenting with a manual switch, I may install a thermoswitch to see how well it works by comparison, and if I decide I want separately controlled cooling of the ATF and engine coolants, I'll install the ATF cooler that has its own thermoswitch and fan.
 

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As usual, there are many ways to solve a problem. I had an interest in doing it cheaply. I had the fan run all the time before I installed the thermal switch, and it was only an issue when the ambient temp went down to the 30's. It took a little longer before the TC would lock up as the fluid did not warm up as quickly. Good luck with whatever you choose.
 

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Discussion Starter · #14 ·
I found a way to use the climate control knob's A/C positions to turn on the radiator fan, without a compressor or clutch connected. There are four wire connections on the back of this knob's switch (and several pneumatic connections--I don't know how they work), and one of these wire connections (purple wire, second connection from the right, when facing the front of the knob) puts out 12V for several positions of this knob, only when the engine is running--Max A/C, Normal A/C, Mix, and Windshield. This connection doesn't put out 12V in the switch's Vent, Off, and Floor positions. So, I ran a wire from this connection on the back of the switch, to CCRM pin 14, snaking the wire inside and under the dash, past the door hinge and under the driver's corner of the hood. Now I can turn on the radiator fan in either of the former A/C positions, and I have two positions that don't turn on the fan, if I want cabin heat or air without reducing the temp of the engine coolant or ATF.

I had to wire up the fan via this long path because I couldn't find a point under the hood where this switch connection's wire terminates, nor another point where 12V becomes active both only when the engine is running, and the climate control knob is set to either Normal or Max A/C. I measured all the A/C-related pins on the CCRM and the PCM, but didn't find one. I even reconnected the coil from my rusted compressor clutch, but that didn't change any of the voltages I measured. The Haynes manual has one of those "typical" wiring diagrams that at least is good enough to imply that what the PCM may be looking for, in order to start the radiator fan when A/C is on, is a certain amount of pressure in the A/C compressor, which closes a switch that may communicate with the PCM. My compressor will never spin again, so I can't reconnect it, and I won't be buying a new one for a while.

Now that I've wired up the radiator fan, I'm not sure I've had a need to activate it yet, since I don't yet have an ATF temp gauge installed, so for now I'm just extrapolating from the engine coolant temp, which hasn't yet gone much past its usual midline after the rewiring, presumably because (as I've confirmed) the fan still comes on automatically when the engine temp goes a little past midline on its dashboard gauge. But since that hasn't always kept the fluids cool enough in previous summers, as the fan cycles on and off even when I think the fluids are hot enough to justify keeping the fan on longer, I may get a chance to get some use out of my rewiring as the temps increase this summer, until after I install a cooler.
 
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