Thread: Electric fan control

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I agree with Itoldyouso.........I had a controller on a fan and also had an over ride toggle switch under the dash. Good thing I did too....one day going to a show the controller went away. I just hit the toggle and the fan was on. I tore out the controller the next day and just left the toggle in. Like everyone else in here, you watch the gauges more than the road anyway.
The controllers are a good thing but in my mind they still have to work from an electric source and if that souce has a problem, the fan will not go on.

Yeah, I went overboard in my last description - it's more applicable to an industrial process control application than a car radiator. The key, like Jerry says is to look at the whole thing as a system and the ability to adjust on-off points is a big plus like both he and Trjohn57 said. I also like the idea of a fail safe toggle to bypass the controller - may be adding one to mine.

Cooling systems that are inadquete are similar to playing musical chairs---as the music goes on and on and you go round and round---when the music stops something overheats.

In both Rogers pattern and the one I described they are a loop and both somewhat do the same thing--

However---In Rogers world he will have overheated his system before RECOVERY begins and in my system, I keep the ENGINE temps where I want them.(Unless in either case there is a failure somewhere)

For those of you that claim to watch the guages---if your system is under capable of cooling your going to blow off some hoses or such----

I had a fan controller stop functioning out on the road. I also had an over ride toggle switch so I could turn the fan on with a flip of the switch. I took off the controller and just left the toggle switch so I can turn it on if I need to. We all know we watch the gauges more than the road so not having to rely on an electric part going south is my way like Itoldyouso.

Looks like I just need to get an adjustable fan switch with radiator drop-in sensor. With those, don't you just turn the dial down, heat up the engine to desired running temp, then turn the dial until the fan comes on?

I also have a manual override switch, but I never have to use it.

There is a small relay that comes with a sending unit. It has a little screw on it that you turn to adjust. If you gauge is at 195 and your fans turn on then and you want to have your fans turn on sooner, then you adjust the screw to where you want the fans to turn on sooner. As for mine, I wanted to have it no more or less than 190. It worked great. As long as you have a clean coolant system, this should do the trick.
Did you understand what I meant about the ground? The sending unit needs the ground wire to be hooked up to it. Just trying to help.

There's nothing you can do that can't be done. (John Lennon)

Originally Posted by jerry clayton

For those of you that claim to watch the guages---if your system is under capable of cooling your going to blow off some hoses or such----

My watching gauges constantlly has nothing to do with the cooling system not being capable of doing the job, it is just my nature to glance at my temp, oil pressure, and volt meter every few minutes while driving. I even do it in my daily drivier. I keep the digital information screen turned on at all times so I can watch what is going on under my hood. I've done it for so many years it is just second nature now.

My hot rods run cool going down the road and most times I don't even turn the fan on at a light, but living in Florida with our heat and humidity, we don't take anything for granted.............even the best engineered cars will run hot down here sometimes.

Don

Don

my info and comments were for vehicles in general---your open car with open engine will not have airflow problems like a closed car--in a closed car such as rogers, the air doesn't flow thru the radiator because it can't exit the confined places under the hood--if the air can't get out, it can't get in(thru the radiator) needs lots of louvers---but they don't do them in glass bodies

Yeah, I know that cars like 40 Fords can have an issue with that...........what is it called, air reversion, or something similar. The air can't escape so new air goes around the radiator instead of through it.

Last night Don and I were working on his car and he said he just saw where some guys on a TV show were talking about how they punched holes in their fan shrouds to allow air to pass through when going down the road. Supposedly it cured a run warm condition that they had previously experienced. I guess that could be true also because one radiator setup I bought had rubber flaps over some holes in the shroud to allow air to escape while driving, but they would suck shut when the fan came on.

We are going to pull out Dons shroud and holesaw some holes into each corner to see if his T will run cooler going down the road.

Don

Originally Posted by jerry clayton

Don
my info and comments were for vehicles in general---your open car with open engine will not have airflow problems like a closed car--in a closed car such as rogers, the air doesn't flow thru the radiator because it can't exit the confined places under the hood--if the air can't get out, it can't get in(thru the radiator) needs lots of louvers---but they don't do them in glass bodies

Mine is pretty open, Jerry, running a solid hood top but no sides. I don't trap much air behind the radiator

Originally Posted by jerry clayton

However---In Rogers world he will have overheated his system before RECOVERY begins and in my system, I keep the ENGINE temps where I want them.(Unless in either case there is a failure somewhere)

Regarding overheating, it's all a matter of selecting the right set points and the point at which you define "overheating", right Jerry? My fan on set point is going to be set slightly above my t-stat setting so I'm not running the fan when my t-stat is controlling to set point, with the high speed on set some span above that based on the cooling capacity of the radiator. Your fan on set point is going to be set at a lower temperature than mine, based on the known/expected heat pickup in the engine. Once adjusted both setups will work just fine, IMO, and neither will allow anything to overheat in normal situations.

...but living in Florida with our heat and humidity, we don't take anything for granted.............even the best engineered cars will run hot down here sometimes.
Don

Man is that right! I learned quick lessons when I migrated down to the gulf coast in the USN years ago with my old '60 chevy. Learned the need for a clean system and a good t-stat pretty quick!!

Originally Posted by Itoldyouso

I've never run an automatic controller, personally. I just have a toggle switch to turn the SPAL fan on when I see the gauge start to get over 180 at a light or something like entering a show. Since I constantly watch all my gauges I feel I have better control over it by doing it manually. Might be old fashioned, but it just works for me.

Don

Until that day when you forget

Originally Posted by Itoldyouso

Last night Don and I were working on his car and he said he just saw where some guys on a TV show were talking about how they punched holes in their fan shrouds to allow air to pass through when going down the road. Supposedly it cured a run warm condition that they had previously experienced. I guess that could be true also because one radiator setup I bought had rubber flaps over some holes in the shroud to allow air to escape while driving, but they would suck shut when the fan came on.

We are going to pull out Dons shroud and holesaw some holes into each corner to see if his T will run cooler going down the road.

Don

my cooling components shroud has the rubber flaps. I never really gave it much thought, but that makes sense.

If you put holes in your fan shroud you will kill the effectiveness of it and might as well take it off--the OEM types with the rubber flaps let air pass thru from vehicle motion but when at slow speeds or stopped will close off and make the fan suck thru the radiator.

I'll just add a couple more notes----use circuit breakers in the current supply lines to the fans, not fuses or fusable links---place your switching mechanisms in the ground circuits for the relays so you don't need high amperage passing thru your switches
You can run a high guage wire directly from your alternator to the relays for the fans so the current doesn't need to go thru your dash---

Don---maybe not in your case---but running without side panels on your hood can cause a turbulance that will destroy the effective differential pressure at the radiator and kill air flow---the best is hood panels and louvers to let the laminar flow down the sides create a suction

That's the nice thing about this car hobby. There are so many different ways to do things and so many diverse opinions of the "right" way to do them...........but somehow the cars seem to still go down the road and function as they should.

Don

Originally Posted by jerry clayton

....but running without side panels on your hood can cause a turbulance that will destroy the effective differential pressure at the radiator and kill air flow---the best is hood panels and louvers to let the laminar flow down the sides create a suction

Jerry, can you help me understand? You're saying that Don's '27T with the open exposed radiator and engine is OK, but for my '33 Hiboy I may have turbulence around the sides of the radiator that will effectively block flow through my radiator? The only thing that could create any turbulence, it appears to me is tires, headlights and perhaps the splash aprons, but I really don't see much difference between the '27 and the '33 for air flow other than the spash aprons and they only extend the frame about 8". Below is a picture of mine head on, for reference. I'm just trying to understand your interpretation of the physical situation here, and what might be causing this potential air flow problem.