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Elec. fan on and off....?

AzPete

AzPete

Well-Known Member
So, according to the electric fan companies, the most popular temp. sensor switch turns the fan on a 185* and off at 175*.

I really wonder what the "off" side of it is for. If one has a 180* thermostat in the engine, the water should never get below 180* in the block or in the thermostat housing where most mount the sensor. Even if the sensor is mounted in the radiator, the actual temp would most likely never get to 175* either.

As for the "on" temp....again, why? If the fan runs from the first start of the car, it would be no different than a regular fan. What is so great about turning it on at a temp. that is higher than thermostat? Saving a power surge during the initial start up of the car?

Has anyone actually had the fan shut off as you are cruising on the highway where companies say you do not need a fan?

Just wondering on the entire logic of having a fan with an on and off option.....
 
During street driving my Spal only comes on when driving really slow like in traffic or sat at a light. It never comes on on the highway or when moving along say at 40-50mph+. It runs all the time when on the track blasting around.
 
The off side is for those cars that let the fan continue to run after the eng is shut down to allow cooling the rad.
Sort of like the headlights that stay on after you leave the car.
 
I can see that...as long as you have a real strong battery or the fan is not that powerful.
 
Pete,

The way that I have my fan set-up is for the fan to come on at about 188°F and turn off at 184°F, with a 180°F thermostat. It's supposed to turn off when I hit 40 mph, but I've got one of the scalars wrong at the moment and it's not cooperating. I don't see a point for the fan to run while the car is moving above 40.

Yesterday, when I drove the car to work, I don't think the fan turned on. I was cruising enough to keep the engine temp down. Even with a higher amp alternator in the car, I can tell when the fan turns when looking at my data logs by a drop in the battery voltage.
 
Since I'm running efi, there the temp sensor on the hard tubes that run to the heater core. IIRC, the sensor is on the tube that's between the intake and the heater core.
 
I use radiator sensors. Why? Because the fan is needed when the radiator is unable to provide cool(er) coolant to the car, not when the temp exiting the engine is above the thermostat set temp. So, I measure the cool side of the rad, cutting off around 140 or so and on at 180 or so. Using this scheme my fan rarely cuts on in normal driving unless I stop. I use this on both my truck and stang. My M5 is wired from the factory this way[nb]Not the usual setup from the factory, but the cost of multiple sensors rather than the best control point drives the decisions at most factories.[/nb], and even blasting around the track, the fan does not come on until I drop speed for a while or go in the pits. Then, it's needed to get rid of residual heat. Above 30 mph or so depending on the car, your fan is not really doing anything - the air pressure at the front of the car is pushing more air through than your fan can.
 
Talked to SPAL this morning. There comment is yes, the fan could shut off if the car runs that cool on the highway but that is not their plan. They say very few classic cars will run that cool. The off side is for those that leave the fan on after the car is off. Also, they recommend the sensor be best placed in the intake, second in the thermostat housing, and third in the radiator.
 
I think they did it just to make you ask questions. When you called them were you actually looking at getting a fan or just being a bored retiree?
 
"blue65coupe" said:
I think they did it just to make you ask questions. When you called them were you actually looking at getting a fan or just being a bored retiree?
Click to expand...

Could be.....

I told them I was interested in an elec. fan system and wanted to know which setup would work better. Asked other questions from there.
 
I just finished installing a fan controller from Delta Current Controls last weekend. What a cool little "black box" controller. It is mounted on the driver side inner fender in the picture. It uses PWM to regulate the fan speed from 0 to 100% based on the sensor in the radiator. Took a few short test drives and adjustments on the temperature control knob to dial it in to my radiator and fan combo, but it now sits right at 185. It has an option for a small LED light that you can mount on the dash that changes colors as the fan speed picks up. Amazing how little the fan really needs to work. It has only come on at idle when sitting at a stop light. On the road pretty much at any speed the fan hasn't been coming on at all. Outside temps have been 70 and below, but even in the summer, I'll bet the fan won't come on at highway speed. Sat in line at the DMV for reinspection on Friday for over half an hour and the fan cycles up and down effortlessly. I highly recommend it.

Mark
 
Hmmm...same fan as I have. I have a Griffin 2 row alum. rad that came in the car. Guess my fan is just destined to run. Keeps the car below 200 with the A/C on. Have yet to see it not turn on based on engine temps. Even in the cool evenings here, the car runs at 180. Everything is in good condition or new....

As the car warms up from a cold start, the temp rises to about 185-190 just before the thermostat opens. As the first rush of cool water hits, it settles at 180. Just before the temp drops, the fan comes on as it is on a 185 on, 175 off. Car never cools down to 175 to shut the fan off.
 
I have this setup, dual electric fans with a larger than life Griffin radiator. The passenger side fan runs all the time, and the drivers side fan is on an adjustable thermostat. At idle the DS fan will cycle with engine temp, or runs all the time with the AC on. I spoke to tech at Old Air products and my concern was the one fan running all the time~ he said, no problem, the fan will last a long time. I just don't like to hear it running when my motor is stone cold! the photo is from a while ago, I since have a 100 amp alternator which works very well and all is hooked up(heater,etc). I have yet to install Pete's tri-gauge setup to watch my engine temp, so I had used a radiator thermometer to see what my engine temp is to set my adjustable thermostat. I'll one day get with tech again to modify how the fans work, but I'm still working on the body of my stang right now. : (
dne'

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