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I bought a "185 degree on" electric fan sensor, but, according to the temp gauge, the fan cut on at about 165 and stays on prettymuch all the time once it cuts on. This is the second fan sensor I have bought because the other did the same. I just thought it was a bad sensor.
The temp sensor and the fan sensor are mounted about 6" apart on the intake. Which one should I trust and which one should be mounted near the thermostat?
I don't have anything scientific to back this up, but I've always felt the spot right at the thermostat housing was the most accurate reading of an engines temperature. My logic is that this is right before the water leaves the engine and should be at it's hottest. I know on my 350 chevy there was a 20-30 degree temp difference when I moved the sender from the back of the block to the front by the water neck.
Don
I use the Spal controllers, I find them to be the best.
Dan just bought one for his rpu.........very impressive unit, heavy duty. Not cheap, but it seems worth it.Quote:
Originally Posted by roadster32
Don
I like spal or derail variable speed, i put the sensor in the radiator tank so you have the option of letting the fan run after shutting the engine off.
if the sensor is for the cooling system fan---why not put it in the radiator near the rad exit back to the engine---after all--isn't that where you want it to be cooler????The thermostat should control the temp of the coolant leaving the engine so you should use the fan to control the temp of the coolant leaving the radiator.
I did not have a port in the radiator so that was not an easy option for me. I'm using a SPAL controller which gives the flexibility to program your "fan on" point, and the "fan high speed" set point independently. I have three ports, one on each side of the intake on the front water jacket runner, and a third on my water neck downstream of the thermostat. My ECU temp sensor was pre-installed in one of the intake runner ports, and I used the opposite port for my SPAL fan controller sensor. My water neck port holds my dash indicator sensor. My thought is that I want to see the blended temp coming out of the thermostat, while the ports right at the head may be slightly hotter (not much, but maybe a few degrees). Running a 195 T-stat I have mine programmed for fan on at 200F and fan to high speed at 215F. SPAL recomends a 15F to 20F differential, so I used 15F.
On yours, you say you bought a 185F Fan On temp switch, and you're concerned that the fan runs all the time. You did not say what T-stat you're running, but if it is 185F or above (which is likely) then it makes sense your fan runs continuously - the T-stat is controlling to a temp at or above your temp switch setting. I like the idea of a controller vs hard switches that have approximate "on" set points and built in dead band for "off" (like maybe 185F on, but must drop to 175F to turn off).
The first pic below is the drivers side intake port, with the ECU sensor; and the second is the sensor in the water neck feeding the dash indicator.
In your second pic, I assume that that is teflon tape on the threads????
Yep, it is teflon tape, but only on the top 1/3 of the threads to ensure that the bottom threads are clean and conducting to ground. I know this because the gauge initially did not work until I re-installed the sensor as described.Quote:
Originally Posted by jerry clayton
OK just checking--
Now--I want to point out that the thermostat controls the minimun temp in the engine
and---the fan controls the temp of the coolant leaving the radiator going back to the engine----so---put the sensor in the lower part of the radiator or possibly lower part of the engine block----
In my mind for a street vehicle if everything is sized right the thermostat will modulate to control to a fixed temperature - with a 195F stat you will run 195F once up to temperature, and it will not vary from 195F unless you lose air flow, your radiator is too small or your water pump drops flow. I like the idea of putting the fan control sensor at the exit of the engine or inlet to the radiator, telling you that the fluid is going to need additional cooling (feed forward control). If you put it on the cooled side (feed back control) then your temp is going swing before you take any action, and if the fan is sized right you will over correct, cooling more than ideal. With feed back control and any component undersized (or low speed operation, low air flow) your operating temp will tend to swing up and down on some form of sine wave. Feed forward will be more stable for the street - just my $0.02.
Look at it this way Roger---we're talking about the fan control--we're varying the amount of air flow thru the radiator --its the only variable that we have any control over--the thermostat will have the coolant coming out of the engine at 195 no matter which of the 3 holes you put your sensors in or even if you don't use any. You need to run the fan only if there isn't enough airflow thru the radiator to cool the liquid down enough to keep the engine under control of the thermostat--the key element here is the temp of the fluid leaving the radiator---so put the sensor at the outlet of the radiator and thru trial and error determine what the temp needs to be---set the controls so the fan comes on as the temp gets up to that temp and shuts off as it falls below that temp
If you care to really get a feel for what is best for power / economy, check the temps in and out of the raiator to find out how much the radiator will drop the temp and then adjust the sensors/thermostats, etc around that data.
I agree, but if you measure your temp at the exit of the radiator and it is too hot then that water is now going to the engine to pick up heat, so when it gets back to the inlet it's now even hotter. By the time your sensor sees cooler temps it will back off on cooling, and start the roller coaster again. If you measure your temp at the inlet to the radiator you start your fan quicker, add cooling to that hot water and minimize the added heat above set point. Feed forward control eliminates most of the trial and error of a feed back control system. Now if you want to really get fancy use both sensors, one on the inlet to the radiator and one at the outlet in a feed forward control with feed back trim. Anticipate the cooling needed and start your fan, then measure how it's doing on the outlet and adjust the speed up or down based on your feed back sensor. Only really effective with a variable speed fan though.... Throw in a little integral action on the feed back loop and you'll run cool as a cucumber.;)
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
When I installed one in my 66 Lincoln, I was able to buy one that was adjustable for the temp that I wanted. Remember that they run with the ground wire. So the ground wire is what controls it, not the other wire.
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)
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.Quote:
Originally Posted by jerry clayton
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
Mine is pretty open, Jerry, running a solid hood top but no sides. I don't trap much air behind the radiator :cool:Quote:
Originally Posted by jerry clayton
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.;)Quote:
Originally Posted by jerry clayton
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!!Quote:
...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
Until that day when you forget http://i65.photobucket.com/albums/h2...ackinmyday.gifQuote:
Originally Posted by Itoldyouso
my cooling components shroud has the rubber flaps. I never really gave it much thought, but that makes sense. :cool:Quote:
Originally Posted by Itoldyouso
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. :rolleyes::LOL::LOL:
Don
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.Quote:
Originally Posted by jerry clayton
Roger nice pic
Altho I have referanced you in several posts, its because you and I and others were discussing something that you kept referring to as how you did yours instead of the issue in general--sorry if it has appearred that I was down on you---
About the turbulance and lack of flow thru the rad--
Your pic shows the a/c condensor and 4 large brackets that reduce/block flow from the front.
If you look at the pic you will see that the radiator is aprox 50% of the frontal area compared to the firewall/cowl area.
This blunt forward facing area can cause interuption of smooth flow of air front to rear of your car and the buildup of pressure in the area under the hood and behind the radiator.
Even if it doesn't completely stop flow , it will vary with speed and maybe cause overheating as the load goes up.
Do you have underdrive pulleys on the waterpump or alternator??and what is the ampereage you electric fan draw?
No underdrive pulleys, and have not measured the actual amperage draw on my fan at low/high speeds. Also have not experienced any elevated temperatures in the first 1000 miles of shakedown driving. The highest temps have been coming off the blacktop, dropping to 5-10mph for the last mile of gravel :eek: back to the house, and then not above 210F.Quote:
Originally Posted by Jerry Clayton
Bulldogcountry1,Quote:
Originally Posted by bulldogcountry1
Sorry to have gotten so far off track on this thread. I believe you will be just fine with that setup. There are a lot of stand alone fan controls out there, some come with relays and some don't, and the adjustment method varies with the package but you're right on target - that's the way the SPAL package is adjusted. You'll want a relay, and like Jerry said above, switching the ground side is best, with a circuit breaker on the hot feed rather than a fuse. Other than that, you've got lots of information :confused: on sensor location, shroud holes, air flow and control theory to consider as you put your system together. Like Don said so well:
Quote:
Originally Posted by Itoldyouso
Some electric fans can pull 30 amps on startup but then drop to between 10-15 amps.
Quote:
Originally Posted by rspears