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Old 07-01-2007, 04:35 AM   #1
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Coolant Fan Temperature Switch

I converted from using a mechanical fan to an electric fan. The wiring set up is a kind of "limp home" style. I have an adjustable fan control temperature sensor stuffed into the radiator and a fuel pump relay. My complaint is that the wiring is all hanging out and the relay and controller hanging on by a few zip ties. Looks like a real hack job! My other complaint is even though it is adjustable, the fan comes on way too cool. If I turn the adjustment the slightest bit, it turns the fan on way too late.

Most stock electric fans are turned on by the ECM. Mine wasn't designed for that. Some though use a dedicated temperature switch, that screws into the engine. I spent several hours researching for different OEM switches, and only came up with finding out that a Pontiac Fiero has one BUT it doesn't switch until 225-239 degrees! too hot for me! Also found out old VW Rabbits (METRIC threading is a disadvantage too.) have one at 190 degrees, that is cooler than the thermostat I have, and want to keep. (thermostat is 195) Ideally I want to keep the temperature of the water at 205 or so. I want it hot like that for fuel efficency, but much more is not good for engine longevity.

Anybody know of any temperature switches that are about 205 degrees? I prefer a OEM (doesn't make which make) part or replacement part, to use as a universal part for a "custom application". Reason being for cost and availability. Prefer 2 speed, because my fan is 2 speed. Thanks for any help!
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Old 07-01-2007, 08:00 AM   #2
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Only thing that I have seen that allows you to set the temp where you want is a variable speed fan controller like this vendor offers below. The variable speed seems like a good idea since it only runs as fast as you need.

http://www.dccontrol.com/

Please post your before and after electric fan FE numbers if you can. Also what type of original fan did ya have, fan clutch, temp controlled fan clutch or direct drive?

My 4 Runner has a temp controlled fan clutch that I have been considering replacing with an electric. I often tow a boat so I'm not comfortable just yet with switching due to concerns that the electric may not cool sufficiently while towing.
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Old 07-01-2007, 09:02 AM   #3
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Quote:
Originally Posted by caprice View Post
Anybody know of any temperature switches that are about 205 degrees? I prefer a OEM (doesn't make which make) part or replacement part, to use as a universal part for a "custom application". Reason being for cost and availability. Prefer 2 speed, because my fan is 2 speed. Thanks for any help!
You might want to look at what I ordered. While it's not yet installed (it's going on with my new radiator, likely this week), I picked up the following adjustable radiator fan controller:
http://www.napaonline.com/MasterPage...ure+Sensor+Kit

Now my car already has control of the radiator fan. However, my feeling is that the fan has been coming on at a lower temp than it really needs to (and lower than is optimal for FE). And with the stock arrangement, I have no way to control it. However, if we modify things to have the fan controlled by this new (variable) thermostat, than it should be trivial (just adjust the temp control) to experiment with different coolant temps and their effect on the engine and FE. Hence my desire to bypass the stock fan control, and instead go with an adjustable thermostat...
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Old 07-01-2007, 09:20 AM   #4
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Those variable temp switches that a lot of vendors like to sell are nothing more than hot water heater thermostats for your house. Completely inappropriate for a car. The problem with sticking a probe between the fins of the radiator is as soon as the fan comes on, the air rushing past sensors will cool it far below the temp of the coolant inside the radiator. It will never give you an accurate temp reading no matter how you set it. The solution is to use a sensor which is in direct contact with the coolant.

This is my electric fan conversion for a volvo. I used a temp switch hose adaptor from a late 80s Saab 900. The hose adapter can be found on the top hose in a Saab with a 115c temp switch. I installed it in the lower hose with a 91c temp switch. New temp switches can be bought at NAPA in any number of temperature ranges. Mine switches on at 91c and off at 87c.
Good luck
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Old 07-01-2007, 10:08 AM   #5
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I also replaced the original clutch fan with an e-fan. I'm using a holder out of a Saab just like what tjts1 showed above, in the lower radiator hose. Fortunately they fit my car's rad hoses perfectly. You can get switches for those T-fittings in various settings at parts stores. Mine comes on at 83 or 85 deg. C and goes off 5 degrees cooler. That operates the fan at high speed.

However mostly my fan runs at low speed only, via a relay activated by the brake light circuit. A brilliant idea suggested from Mapleleafer of turbobricks.com, who's mom's car kept overheating at stops. Brilliant because it ensures there's always at least a slight breeze over the radiator - so the engine doesn't have to heat up past some trip point for the fan to come on. That way, it mimics the clutch fan more closely than temp sensors do.

At highway speeds you really don't need to worry about switching the fan. I doubt there are many (any?) fans that provide more air speed than highway road speed. Mine does come on if I charge up a hill at wide throttle - well, I used to do that! But the fan is not what cools things down in a climb, it's the downhill at low throttle that cools things off.
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Old 07-01-2007, 11:05 AM   #6
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The electric fan is extremely quiet. Chances are you can't hear it over the engine at idle.
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Old 07-01-2007, 03:19 PM   #7
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The electric fan is extremely quiet. Chances are you can't hear it over the engine at idle.
Quite true. When driving I don't even hear it when fan is on high speed. I'm pretty sure he did tell his mom what he did but that's another story on another board, two or three years ago.

For my system, I rigged a dash LED that shows when fan is on. It doesn't tell me which speed but I know if my foot is on the brake or not so that covers it for me.
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Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
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Old 07-02-2007, 01:07 AM   #8
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Originally Posted by tjts1 View Post
The problem with sticking a probe between the fins of the radiator is as soon as the fan comes on, the air rushing past sensors will cool it far below the temp of the coolant inside the radiator. It will never give you an accurate temp reading no matter how you set it. The solution is to use a sensor which is in direct contact with the coolant.
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Exactly what I am thinking. I found this web site that gives the specifications of ALL switches! Freaking awesome. http://www.wellsmfgcorp.com/~wellsmf...&submit=Submit All I got to do is pick one, and go to Checker Autoparts.

I switched to a small electric fan out of a V6 Camero the same time that I did the motor swap. It's too small. Daytime temperature are over 110 degrees here in Phoenix. It runs constantly during the day, and intermittently at night. It probably is taking more power to run it than a mechanical driven fan. Power loss by converting the energy to electric, via the alternator, power loss by the electric fan motor. I scored a radiator fan out of a Lincon Mark VIII for only $20. According to a lot of forums on the internet, these move a lot of air, and has no problem cooling large engines. This thing is a monster, I think it is bigger than the original fan. It has 3 wires: ground, high speed, and low speed. I am thing of putting in two sensors, one at about 205 to engage the low speed and one at 220 for full speed.

Thank you for the responses. I just scanned over them, will read them better tomorrow when I have more time.
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Old 07-02-2007, 01:16 AM   #9
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You want the radiator fan to come on 10 degrees after the regular thermostat, right? Or is it 5 degrees?
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Old 07-02-2007, 05:41 AM   #10
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I've been told that the fan you've got...that Lincoln Mark VIII?? Same as the 2 speed Taurus fans....One of the best E-fans you can get out of a junkyard. I'm going to put one in my Jeep.....figured I would wire the low-speed up to the ignition (always on), then wire the hi-speed to both the OE wiring for the aux fan, as well as a manual switch.
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