Electric fan control switch

1FATGMC · January 29, 2008, 05:51:14 PM

Quote from: "enjenjo"Ok, the reason you don't want it to turn on and off at the same temperature.

The toughest part of an electric motors life is the start up. It draws more current, and loads the windings more. If the on/off temps are the same, as soon as it starts, drops the temp one degree, it shuts off. Almost immediately, the temp goes up, and it starts, the temp drops, and it shuts off. Over and over. Real hard on the fan motor..............

I agree with all of that, but the question was how is it ever going to turn off if the turn off point is below where the thermostat operates at???

If you have a 185 thermostat it seems to me you would want it to turn on say just over 200 and off above the 185 deg. the thermostat will close at. That way if the temp goes up for an intermittent reason the fan will come on and as the temp drops back towards the thermostat temp it will go off.

I have a 185 thermostat in my truck. The temps climbing a long hill with the teardrop can get into the mid 190's, but after the hill will drop back down to 185. I wouldn't want the fan to come on at 190 and then never go off as the temp never goes back down to 170. I have a mech. fan anyway in the truck, but do have a pusher that I can manually turn on if I want like cruising at really slow speeds through the crowds at a car show or in Phx. in 115 deg. weather and on the surface streets.

Also at speeds over 30 isn't the fan just getting in the way anyway?

c ya,

Sum

phat rat · January 29, 2008, 06:03:40 PM

It sounds as though you might as well have wired it direct. As others have said once it kicks on it won't be shutting off until you stop

Okiedokie · January 30, 2008, 10:42:07 AM

So then I am back where I started. What Sum says makes sense to me, I will make sure that the lower temp is higher than thermostat temp if I go with the two temp switch. A sensor that is on/off at same temp would be best though it seems to me. Isn't that what yours does phatrat? When you are stuck in slow moving traffic and your temp hits 200, your fan comes on and stays on untill it drops below 200?

enjenjo wrote:
the fan starts and stops a lot.

We have a winner........................

Why would the fan start and stop any more than with phatrat's setup, or others with adjustable setting at one temp to turn on fan?

phat rat · January 30, 2008, 11:06:55 AM

I can't remember the difference but there is some. It doesn't cycle continuously but will come on frequently when in traffic jams. This is only an auxiliary fan as I run a mechanical fan with a shroud. It's just a little added insurance against overheating.

Bugpac · January 30, 2008, 12:26:20 PM

first off, you dont want your radiator fluid the same temp as the engine fluids...the t stat lets hot water out, you need to have cool water going in the motor, thats how the engine temps stay on a flat plane, if your pumpin 190 degree water in a engine with a 190 t stat, its gonna run hot....Id get a on at 195 off at 175 for a 190 t stat if it was me....As the fan is cooling the radiator not the engine....

Bugpac · January 30, 2008, 12:28:29 PM

Oh ya, all fans are not created equal either, some will do more harm than good, if they cant move enuff air they become more off a restrictor than anything...

enjenjo · January 30, 2008, 12:30:33 PM

QuoteWhy would the fan start and stop any more than with phatrat's setup, or others with adjustable setting at one temp to turn on fan?

Because as soon as it cools off, even one degree, the fan will shut off. With a 5 to 10 degree diffence in the off/on temp, it will run longer, and shutt off longer before coming on again. Much less wear on the motor.

enjenjo · January 30, 2008, 12:32:59 PM

Quote from: enjenjo
QuoteWhy would the fan start and stop any more than with phatrat's setup, or others with adjustable setting at one temp to turn on fan?

Because as soon as it cools off, even one degree, the fan will shut off. With a 5 to 10 degree difference in the off/on temp, it will run longer, and shut off longer before coming on again. Much less wear on the motor.

38HAULR · January 30, 2008, 03:23:11 PM

Interesting discussion. I have noticed though,a few of the posts referring to the fan sensor being on the lower radiator tank. Is this ideal?. The hottest part of the cooling system would be the top tank or the exit area of the engine,the lower tank would have been subjected to cooling ........Frank.

Okiedokie · January 31, 2008, 10:00:09 AM

Frank I agree with why would you put it in the bottom tank, but that is how many are designed. Now for my last post on this subject. I found in Jegs catalog that they show two temp sensor switchs for electric fans. One is 185 on and 170 off that they describe as for 180 degree thermostats and then one that is 200 on and 185 off for 195 degree thermostat. Thanks for everyones input. My next step will be to use my laser temp sensor to test at what temp the thermostat opens in my 46, then what temp fan comes on and then goes off, and how the thermostat reacts. Joe

Pep · January 31, 2008, 06:14:28 PM

Just to add to this, I may have jagged it, but I bought a sensor off a Mazda that appears to be a 190. I put it into a hole in the water pump that had a brass plug in it. It starts the fan dead on 190 and turns off at 180. I recall I have a 180 thermostat. It all seems to work fine, but the thing I did take note of, was I wired the fan relay to the ignition switch. I didn't want the fan on after I parked the car, as we all know, engines get hotter once you park them, so it would be on most of the time after I walked away. I don't like doing that....But, I did have the accessories wired to the relay, so in the event of the engine getting to hot and I needed to cool it down while parked, I just turned the key to accessories and let the fan do its thing.

38HAULR · February 04, 2008, 11:21:39 PM

Hi Pep. Looks like some electronic expertise can come in useful for a timed shut off after exiting/shutting down vehicle........Frank

PeterR · February 05, 2008, 03:46:28 AM

Quote from: "38HAULR"Hi Pep. Looks like some electronic expertise can come in useful for a timed shut off after exiting/shutting down vehicle........Frank

Use a turbo timer. Build it yourself kits are about $30.

wayne petty · February 05, 2008, 04:24:10 PM

just thinking... turbo timer for the cooling fan...

the early 90's mopar turbo cars had a fan relay that would run after the engine was shut off... i seem to recall the fan overide switch was on the leg of the fan support so the fan stayed on until the air flow cooled off... i will look for diagrams and part numbers later tonight..must veto now...

also flappers in the sides of the fan shoud to let ram air pass the fan...

filling the area directly infront of the radiator/support with rubber/neoprene sheets forces ram air through the radiator at speed... as there is no way an electric fan could keep up with it...

the power steering pump powered fans off early 90's camrys...

i also have a manometer... dual port inches of water pressure gauge.. i have used it on my sisters 85 t/a a long time ago to see how much pressure the factory air dam was building up under the nose of this bottom breathing car... the pressure was lower in front of the radiator above 58mpg.. when i installed the 4 or 5 inch talled rigid plastic replacement air dam from the dealer... the pressure was always greater infront of the radiator finaly.... the car would only overheat when going over 55...

for gm fan motors... there are differnt strength motors available... amp ratings... i did see and copy years ago a chart that showed amp draw to gm part number.... but i do not have it...

Pep · February 05, 2008, 04:27:34 PM

The funny thing is when I park after a drive, and I sometimes turn the ignition to accessories so I can play the stereo. The fan will come on for a minute or so, then cut off. After a minute it will come back on and repeat this about 4 or 5 times. I assume the heat is being convected through the radiator even though the water pump is not going. Keep in mind, my sensor is in the water pump.