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Old 03-01-2006, 05:53 PM
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Electric Fan On/Off Control.....Location ...Location....Location

This has become a real PITA..!! Running a 502 BB in my 65 Corvette.. I'm using the DeWitts Large Rad with 2 Spal Electric Fans. The Thermostat is a 190* The senser is an ON at 195...AND OFF at 185.

The senser is mounted in the top of the thermo housing above the thermostat. Ok....I know thats the problem. The fans won't turn off while cruzen down the interstate. They run all the time.

I was thinking of monting the senser in the CYL head where it should go. But.. a friend of mine has his their and says he has the same problem. Fans keep running. His is also a Spal fan with the same senser.

Ok I went out and bought a Spal PWM adjustable programable unit that you can set to turn on and off where you want and also... it controlls each fan seperatly and use a multi speed function.

Now I am being told by other experts that even though I mount it in the cyl head where the Mfg suggests it goes.. that I will have the same problem because the cyl head temp is around the same as the water outlet temp.

In other words I won't be able to get the temp at the head down to 185*.

I want to keep the senser in the motor and not deal with sensing temp at the rad with one of those probe adjustable controllers.

Do any of you run the senser in the cyl head? and Do your fans shut off when cruzen the Highway?

Or what else would you suggest...Thanks..

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Old 03-01-2006, 06:55 PM
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The cylinder head is where the heat is created. It's the best place for the sensor.
If the water temp. (in the head) exceeds the setting of the controller, the fans should run. This forces more air thru the rad. and helps reduce the temp. of the cooling system.
Usually, when the car is moving, there is enough air flowing thru the rad. to cool the engine.
If the coolant temp. is OK during long periods at idle then increases when the vehicle is moving, you have some other problem besides the fans.
Look for incorrect ignition timing or restricted flow of air thru the rad.
Also, check for proper rotation of the fans. They need to blow air or suck air thru the rad. from front toward the back (of the car).

vicrod
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Old 03-01-2006, 06:55 PM
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i have one of those probes in the radiator. its just pushes into the fins. i also have a led on the dash to tell me when its on. at first i thought this to be a cheezy setup(other than the led). but its works flawlessly.

not what you wanted to hear. but i thought i would say it anyway.
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Old 03-01-2006, 07:23 PM
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Put a 180 degree thermostat in it.


Larry
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Old 03-01-2006, 07:38 PM
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Quote:
Originally Posted by vicrod
The cylinder head is where the heat is created. It's the best place for the sensor.
If the water temp. (in the head) exceeds the setting of the controller, the fans should run. This forces more air thru the rad. and helps reduce the temp. of the cooling system.
Usually, when the car is moving, there is enough air flowing thru the rad. to cool the engine.
If the coolant temp. is OK during long periods at idle then increases when the vehicle is moving, you have some other problem besides the fans.
Look for incorrect ignition timing or restricted flow of air thru the rad.
Also, check for proper rotation of the fans. They need to blow air or suck air thru the rad. from front toward the back (of the car).

vicrod
Thanks For your Reply Vicrod,

Timing and ignition are dead on...Both fans are running in the correct rotation.
There is plenty of air flow thru the Rad .It's a brand new unit. In fact it is a large Rad and does cool the 502 quite well.

The comments that I have received is that the senser will not function correctly in the head due to the fact that the coolant won't go down to 185* because of it's location in the head.

Again ..I haven't moved it their yet. I just wanted to calify that it will in fact will be able to see 185* at the senser when the fans are running to shut them down.

Do you think the temp in that senser location will be able to see 185*?

Thanks again..
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Old 03-01-2006, 07:43 PM
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Quote:
Originally Posted by Vortech 4.3
i have one of those probes in the radiator. its just pushes into the fins. i also have a led on the dash to tell me when its on. at first i thought this to be a cheezy setup(other than the led). but its works flawlessly.

not what you wanted to hear. but i thought i would say it anyway.
Heh Vortech, Thanks ..

The fin spacing in the Dewitts rad is very narrow. I have a Painless controller with the probe but it won't fit in the fins. That was bought as Plan "B" but I'm not happy with those probe controllers. I know they work but I wanted to use the Spal "FAN-PWM" controler withe the Vari speed controller and temp set.

But Who knows I might go to Plan "B"...But you would think that the cyl Location should work..
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Old 03-01-2006, 07:44 PM
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Quote:
Originally Posted by coldknock
Put a 180 degree thermostat in it.


Larry
Heh Larry.. I thought of that... I got that in line as Plan "C"....
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Old 03-01-2006, 07:47 PM
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Vette

I'm running dual Spal fans with the 180 degree sensor in the driver side head. My fans shut off at 170 even sitting in traffic. The aluminum radiator helps alot. I had to resort to this set-up after sitting on the freeway in traffic during several trips to the track during the summer ( temp gage hitting 230 and blood pressure rising rapidly). Don't even ask what this rig cost. My very understanding wife popped for the whole thing as a Christmas present. I used the radiator probe on my pickup fan and after some adjusting and driving it seemed to work OK. I'm just not real fond of poking things into the radiator fins and tubes.

Oljoedog

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Old 03-01-2006, 08:00 PM
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Listen to Coldknock and go with your plan 'C'. Install a 180* thermostat.

How do you expect to have the temp drop to 185* and shut off the fans when the themostat keeps the temp at or above 190*????
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Old 03-01-2006, 08:14 PM
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well. if the temp is 195 at the stat. its going to be 210, or there about, in the head. so try setting your controller to 210.
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Old 03-01-2006, 08:23 PM
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Quote:
Originally Posted by Oljoedog
Vette

I'm running dual Spal fans with the 180 degree sensor in the driver side head. My fans shut off at 170 even sitting in traffic. The aluminum radiator helps alot. I had to resort to this set-up after sitting on the freeway in traffic during several trips to the track during the summer ( temp gage hitting 230 and blood pressure rising rapidly). Don't even ask what this rig cost. My very understanding wife popped for the whole thing as a Christmas present. I used the radiator probe on my pickup fan and after some adjusting and driving it seemed to work OK. I'm just not real fond of poking things into the radiator fins and tubes.

Oljoedog

Live long race hard
Yeah that costs some bucks..I know where your at dollar wise ..I'm there too.

So then yours is in the head and shuting down... Good to hear.
My Vette runs at 185 to 190 in traffic in 100* outside temps. It's just turning the fan off Tha's Pe-oding me.
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Old 03-01-2006, 08:27 PM
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Quote:
Originally Posted by 32vicky
Listen to Coldknock and go with your plan 'C'. Install a 180* thermostat.

How do you expect to have the temp drop to 185* and shut off the fans when the themostat keeps the temp at or above 190*????
The Coolant entering the block and rising to the heads is cooler then at the exit at the thermo housing. Oljoedog has stated that his senser in the driver side cyl head is doing the job and is working ok.
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Old 03-01-2006, 08:30 PM
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Quote:
Originally Posted by Vortech 4.3
well. if the temp is 195 at the stat. its going to be 210, or there about, in the head. so try setting your controller to 210.

Quote:
I'm running dual Spal fans with the 180 degree sensor in the driver side head. My fans shut off at 170 even sitting in traffic. The aluminum radiator helps alot.
As per Oljoedog
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Old 03-02-2006, 01:12 AM
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Doc here,

Just a thought here..

Have you tried checking the CALIBRATION the sensor yet?

Put it in a pan of boiling water, (212) and a DVOM calibrated on R X 1 (000 on crossed probes) between the center conductor and ground..

Stick a lab thermometer (Or one you trust) in the pan and note the differences as the temperature declines to a point of shut off..

When the meter goes from 000 to infinite, it's off..note the lab thermometer reading at that point..It may be way off..

Just an Idea..

Doc
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Old 03-02-2006, 09:17 AM
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Quote:
Originally Posted by docvette
Doc here,

Just a thought here..

Have you tried checking the CALIBRATION the sensor yet?

Put it in a pan of boiling water, (212) and a DVOM calibrated on R X 1 (000 on crossed probes) between the center conductor and ground..

Stick a lab thermometer (Or one you trust) in the pan and note the differences as the temperature declines to a point of shut off..

When the meter goes from 000 to infinite, it's off..note the lab thermometer reading at that point..It may be way off..

Just an Idea..

Doc
Heh Doc,
Thanks for the reply...I have a mechanical temp gauge in the thermo housing that I got from Jeg's. The senser ( Which I will be movimg to the cyl head) is next to it in the same housing.) I do also have a Cooling system glass Thermometer which I have checked against the one from Jeg's. The Jegs unit is dead on.

I have watched the motor warm up and the senser kicks in at 195* as per spec of the senser and the fans come on. It has on very few occasions shut down when it was supposed to. But that is rare. So.. I'll move it to the CYL as per Oljoedogs post and will see what happens.

The Rad is a monster and cools my 502 down like a rocket. So I know I have the Rad sized correctly for the 502.

Here's the Rad and Fan Combo I'm using..
http://www.dewitts.com/pages/product...asp?ProdID=266
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