Radiator fan switch location

Jokester · November 18, 2004, 08:37:46 AM

Hi experts,

33 Chevy sedan, 327/350, A/C. Where is the better location for a radiator fan switch and the temperature gauge sender? I have outlets in the driver's side head and in the intake manifold. Which should go where? I guess the real question is which part of the engine is hotter?

Thanks,

.bjb

rooster · November 18, 2004, 08:53:28 AM

For the temp gauge I took it off L side next to #1. My fan swt had its own sensor and took water temp with a prob stuck in raditor. I mounted it on fram rail next to the raditor. Fan relay had it own wire to the Battery fused. Wire in loom kit on/offed the relay. Works fine for me.

no expert here!

GPster · November 18, 2004, 09:43:30 AM

Could start a discussion with this one. Suppose for efficiency an engine runs best at 180 degrees at 9# pressure. So you have put a thermostat in it for that temperature so if the water gets hotter than that circulation is allowed. The water pump pushes fresh/cooled liquid into the motor to force circulation through the motor and out the thermostat to the radiator. Your radiator fan is not cooling the engine so that it won't get above 180 degrees, it is cooling the radiator and only telling it that the water it is getting is hot. There is no indication in this system to show if the radiator is working or if it needs the help of the fan. Also do you need to introduce water into a motor that has be cooled to 100 degrees if you are storing in the passages water that is above 180 degrees (the thermostat would be open if the water is moving). In my theory it would be best if the control of the fan was placed in the lower radiator outlet to let you know if the radiator is working or if it needs the help of the fan. Maybe it should be set close to the rating of the thermostat so that the temperature shock to the engine would be less. I'm not trying to be a know-it-all and I would welcome any "Real World" examples to dispute this theory so I could learn more. GPster

Dave · November 18, 2004, 06:49:02 PM

Quote from: "GPster"Could start a discussion with this one. Suppose for efficiency an engine runs best at 180 degrees at 9# pressure. So you have put a thermostat in it for that temperature so if the water gets hotter than that circulation is allowed. The water pump pushes fresh/cooled liquid into the motor to force circulation through the motor and out the thermostat to the radiator. Your radiator fan is not cooling the engine so that it won't get above 180 degrees, it is cooling the radiator and only telling it that the water it is getting is hot. There is no indication in this system to show if the radiator is working or if it needs the help of the fan. Also do you need to introduce water into a motor that has be cooled to 100 degrees if you are storing in the passages water that is above 180 degrees (the thermostat would be open if the water is moving). In my theory it would be best if the control of the fan was placed in the lower radiator outlet to let you know if the radiator is working or if it needs the help of the fan. Maybe it should be set close to the rating of the thermostat so that the temperature shock to the engine would be less. I'm not trying to be a know-it-all and I would welcome any "Real World" examples to dispute this theory so I could learn more. GPster

Ya sure Joe get sumpin started.LOL You amaze me sometimes youve got a thoery for most everything and its usually the right one...
I put my temp sender in the intake on 3 cars now and it sems to work fine the fan t stat im usung is in the lower tank of the radiator and i used an ajustable one and it seems to work fine also. i realise the temp sender should be in the cylinder head but i can run the wires neater if i put it in the intake.. But thats just me............
Dave

WZ JUNK · November 18, 2004, 07:56:29 PM

I like what Joe had to say and it makes sense but I do not do it that way. I usually put the fan switch in one head and the temperature switch in the other or in the intake. Just today I had to install one in the head with a T fitting as it also has a nipple for the heater hose connection. I had to do this because I could not get the plug out of the other head and the engine has a blower and it is designed in such a way that I could only use the intake for the temperature. It might not be the best way but it works. I figure the temperature is just a reference to see if there is a change in the engine and once a fan comes on, most of the time they stay on.

(If this does not make much sense it is because I am hurrying as I am between coats of paint)

Dirk35 · November 19, 2004, 09:14:15 AM

VDO gauges instructions say to put it in the intake manifold with a "T" fitting, as the head will run hotter than normal due to exhaust heat and can cause false readings.

Jokester · November 19, 2004, 10:01:14 AM

Thanks all, it's going in the head. I previously had it in the thermostat housing. That worked OK except for the time before the t-stat opened. The engine temp would climb quickly to about 240 before the fan kicked on. Once the thermostat was opened the fan stayed on all the time, which was fine. I just didn't like that 240 spike when I was first climbing onto the interstate.

Thanks for the info.

.bjb

rooster · November 19, 2004, 10:56:13 AM

240 degrees sounds like alot to me.................................................
If the t-stat is not open the fan has nothing to cool.

My fan relay work independently from any guage readings. Its signal sorce is the temp of the water in Rad, The relay is adjtable to your liking and cycles as needed.....................................................................

The guage I have is the colored kind green yellow red, ele pick up,wired to the left side head . it was a freebe! From a fork lift. Not know what the water temp actully was I installed a additional mech temp guage to see actual degree readings ( at the t-stat). I tested the guage in boiling water to see if it was right. It was! Water temp go's to 190 , t-stat opens, circulation is under way, fan kicks on before 200, stays on until 190, driving or in Park. Your fan should only run if needed. Why so Hot?
stock 350,
auto,Alu Raditor, 16" ele fan.

GPster · November 19, 2004, 11:34:34 AM

Quote from: "rooster"240 degrees sounds like alot to me, Why so Hot?

If the thermostat hasn't opened yet the fan switch is seeing stagnate water . The port in the thermostat housing is downstream of the thermostat and is not seeing flow until the thermostat opens and the thermostat is set to react to the water temperature that it sees, which is not moving and is in the intake manifold which may be somewhat statically cooled by the flow of cool outside (intake) air. There are all sorts of practises but if you want to tell you should check at the heads to see how hot the hottest place is. And if you want to see if the radiator is working you should see what it has done (at it's outlet) not what it's being asked to do. It's all differant whether the water is still or the thermostat is open. I'm noy scolding,just answering the question. GPster

rooster · November 19, 2004, 12:08:49 PM

If Jokster does not desire 240, maybe its a bad t-stat or opens at to high temp. I have heard of high flow t-stats. Jokester may have fuel inj and require more temp but not that much! My thoughts!

Joe.Im going to send you PM concening 50 chevy ribs.

GPster · November 19, 2004, 12:28:27 PM

Quote from: "rooster"

Joe.Im going to send you PM concening 50 chevy ribs.

According to the bible that may be a way to tell if it's male or female. I took my medicine, maybe I need a nap? GPster

HOTRODSRJ · November 19, 2004, 07:51:32 PM

I would like to offer some input here if I might? You know I don't know much about paint and other issues, but cooling is my life! So, here is what I know.

The most consistent place to put a water temperature gauge and/or a sensor is the intake position. If you think about this it also has the advantage of representing/sensing BOTH banks.

The problem with head sensing positions is that they become heat tainted from headers and make them inaccurate with regards to water temperature per se, but less so with iron manifolds. Also, another downside is that one bank of cylinders could have a problem and the sensing side NOT, therefore you could theoreticaly burn one bank up and not appreciably be noticed/sensed? This is the exact thing that caused OEM manufacturers to go to a "centralised" location sensing total water jacket output temperature.

In-so-far as putting sensors in the radiator tank, the problem with this is that the bottom of the radiator tank can change temperature drastically depending on the ambient temperature of the incoming air......and how much airflow you have. It's never a constant and does not represent what is coming out of the engine or what the temperature INSIDE the engine is. While many a manufacturer has made adjustable switches just for this, the ENGINE OR INTERNAL COOLANT temperature at which the fan switches on will vary all over the place depending on outside temperature and airflow.

The "peaking" just before the thermostat opens ...that you are seeing on the temperature gauge as it's sometimes referred to, is due to super hot coolant that has migrated to the top of the system and this enables the thermostat to open. A 240 degree peaking is not a big deal because most of the coolant under that location will be significantly lower. Sometimes super heated gas that is trapped in the system will also give you these high and wildly swinging indications. However, I would use a "balanced" thermostat which takes alot of this away. See more here http://performanceunlimited.com/illustrations/thermostats.html

Also, themal "shocking" of the engine (and cracking blocks) is a myth with all due respect. The engine goes thru dynamic coolant temperature swings (and is designed for such) all the time. Sometimes very cold coolant (at outside ambient temperatures) will flow into the pump and thus the engine when the at the top of the engine the thermostat flys open and ushers in a huge gulp of coolant right off the bottom of the radiator. I would not worry about this at all. Marine engines really get "shocked" like this as well.

I hope this helps somewhat.