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Location:
Vic
Registered:
May 2002
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thermo switch placement
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Sun, 07 March 2004 05:48
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Ive purchased a switch to use on my RWD 4AGE.
I was thinking that the easiest place to have it would be in the radiator but noticed the the top of the radiator gets very hot while the bottom can be cold.
I assume that the best place to have it would be at the bottom of the radiator somewhere.
What have others done?
Thanx
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Location:
NSW, East Coast
Registered:
July 2003
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Re: thermo switch placement
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Sun, 07 March 2004 10:53
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Although i havent installed my thermo fan yet i will be placing the sensor somewhere along the top radiator hose.
Place it underneath the hose to help hide it.
just a suggestion?
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Location:
Vic
Registered:
May 2002
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Re: thermo switch placement
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Sun, 07 March 2004 10:58
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i purchased a new sensor for a laser($35) its normally closed to suit the standard relay.
I didnt think it was a good idea to have it at the top of the radiator cause the top gets very hot before the rest does.
This would cause the thermo to start up before its needed.
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Location:
NSW, East Coast
Registered:
July 2003
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Re: thermo switch placement
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Sun, 07 March 2004 11:07
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As the hot water enters at the top of the radiator it falls thru to get cooled, i believe having the temp sensor there will give good control of the fan going and stopping.
Someone else may have other ideas but i will be trying there first.
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: thermo switch placement
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Sun, 07 March 2004 11:13
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Yep I agree, the top is best. This is where its fitted in cars from the factory.
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Location:
1st street on the right
Registered:
November 2002
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Re: thermo switch placement
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Sun, 07 March 2004 11:33
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I have always put them in the top but them I just thought as I read this if it's in the top the it's turning on before the radiator has the chance to do it's job and would be turning on prematurely. Not that mine will be moving but just a thought.
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Location:
Canberra
Registered:
October 2002
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Re: thermo switch placement
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Mon, 08 March 2004 03:55
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i tried putting it in the top hose, but cant get the hose to seal, so it leaks 
any tricks, good type of clamp to use ?
i was using a 2 ring clamp, which you tighten by turning the screw.
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Location:
Melbourne
Registered:
August 2003
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Re: thermo switch placement
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Mon, 08 March 2004 05:02
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You shouldn't try to just poke the probe under the ring clamp, if the surface isn't smooth where the hose seals then it never will, hose clamp or none!
Cut and shut a piece of pipe (only need be ~3") into the top hose and tap a thread for your temp probe into that. Make sure to leave at least 1" (preferrably more) for the hose to bite onto and consider belling the end of the pipe section (like OEM water fittings) to ensure a secure join.
If your stock temp sender (for dash guage) has an output signal compatible with your switch you could splice in and use that for your signal.
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Location:
1st street on the right
Registered:
November 2002
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Re: thermo switch placement
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Mon, 08 March 2004 06:59
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There should be a rubber seal that goes on the neck of the rad, under the sensor. Comes with the unit (not the fan) that should be the problem.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo switch placement
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Mon, 08 March 2004 09:41
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my 2c ...
the top coolant outlet and top rad tank should see a reasonably stable temperature (assuming the cooling system is working properly)...
the BOTTOM rad tank will see wildly varying temperatures depending on how effective the radiator is working. and what effects the funcion of the radiator? the amount of air going through it...
either way, the temperature of the coolant exiting out of the bottom radiator tank will ultimately be reflected in the temp coming out of the top of the engine.
AS SUCH - it make FAR more sense to run the switch off the bottom of the radiator tank where the switch can regulate the FUNCTION of the radiator, and stabilise its output temperatures (which will then be reflected in coolant outlet temp stability).
running the switch off the coolant outlet or top radiator tank is like catching the bull after its left the gate... ie the radiator has MALfunctioned, temps have gone up, and noww youre corecting the functional error by switching on the fans.
MUCH better IMHO to run the switch based DIRECTLY on radiator functional status - ie bottom tank. that will keep the running temp stable as anything.
it takes a bit more beffing around to get a bottom mounted switch to work though 
PS - many factry cars run bottom mounted switches
cheers
ed
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Location:
Rocklea qld
Registered:
February 2003
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Re: thermo switch placement
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Mon, 08 March 2004 10:46
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If u purchased a switch for a laser u need to put it where the laser one is. Firstly find what temperature it starts the fan at then find the place on the engine that has that temp. Lasers usually go near the thermostat housing. Best best would be take it back and get an adjustable one that goes in the top hose. Then u can adjust the fan to turn on when u want.
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Location:
Rocklea qld
Registered:
February 2003
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Re: thermo switch placement
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Mon, 08 March 2004 10:48
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Whatr about if u have a bit of bloackage in ther radiator. It then slows the flow down which means the water gets to the thermo sender slower there for the water stays in the engine longer which then gets hotter. Thats why most of them are near the temp sender.
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Location:
NSW, East Coast
Registered:
July 2003
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Location:
Vic
Registered:
May 2002
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Re: thermo switch placement
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Mon, 08 March 2004 11:10
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it switches on @ 90 & off @ 85
I goind to borrow a temp probe tomorrow & check the temps all over the radiator at normal operating temp.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo switch placement
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Mon, 08 March 2004 11:31
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| FKN16V wrote on Mon, 08 March 2004 22:10 |
If the radiator wasn't able to keep up (slow traffic on hot days)
wouldn't it be better to get the temp reading straight from the heat source (motor) otherwise you just heat soak the radiator and then the fan/fans would have to catch up "so to speak".
I understand what ed-ma61 is saying and in a way he's right, but i believe my theories will be better of in the long run.
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my point exactly - if the radiator isnt able to keep up the temp at the BOTTOM tank immediately goes up.
the heat source from the motor is the same all the time - its not like the engine starts making more heat, its that the radiator isnt releasing the heat - and this is what you have to measure and base your switch point on.
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Location:
NSW, East Coast
Registered:
July 2003
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Re: thermo switch placement
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Mon, 08 March 2004 12:13
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So your saying (for example) that if im driving down the road doing 80kms and the temp of the coolant in the top hose is (for example) 85 deg, 2 mins later im sitting at traffic lights for a few moments ( say 28 deg day) (no fan/fans)my coolant temp will still be 85 deg in the top hose. I think not. You wrote/posted "the heat source from the motor is the same all the time".
Im not saying your theories/knowledge is wrong or incorrect, im saying that i believe it would be better to take the temp from the top.
Im beginning to like this?
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Location:
Vic
Registered:
May 2002
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Re: thermo switch placement
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Mon, 08 March 2004 12:24
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wouldnt it best to have it at the bottom cause thats where the motor gets the water from.
no point having the thermo come on cause the water at the top is hot but the motor is sucking in cool water from the bottom.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: thermo switch placement
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Mon, 08 March 2004 12:24
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my my aren't we argumentative 
LOl 
" Im not saying your theories/knowledge is wrong or incorrect, i'm saying mine is better :D" heh heh
it comes down to persoanl preference. if you regulate by engine temp/top hose temp, the fan will stay on and off for longer periods, if you regulate by the bottom of radiator, it will turn on and off more often, depending if radiator is doing the job. both ways work, and it depends on your preference, and what temp the switch is for, and what temp your engine likes to run at.
if the radiator can't keep up on hot days in trafiic, then it just can't keep up. doesn't matter then if temp is taken from top or bottom cos they will both be hot
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: thermo switch placement
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Mon, 08 March 2004 12:24
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| FKN16V wrote on Mon, 08 March 2004 23:13 |
So your saying (for example) that if im driving down the road doing 80kms and the temp of the coolant in the top hose is (for example) 85 deg, 2 mins later im sitting at traffic lights for a few moments ( say 28 deg day) (no fan/fans)my coolant temp will still be 85 deg in the top hose.
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no, and the reason it wont be is because the radiator has stopped functioning - the coolant exiting the bottom of the radiator is now hot as shit... you need to detect this drop in raditator function by measuring the temp in the bottom tank so that you can switch your fans appropriatly - thus maintaining adequate heat transfer.
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Location:
Brisbane
Registered:
February 2003
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Re: thermo switch placement
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Mon, 08 March 2004 12:43
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which i suppose is why a more modern car would have sensors in top & bottom tanks (as well as motor head and in the Intake) and would use all of that data to decide when to startup thermo fans, when to go easy on engine power output and (if it's smart enuf) shut down a cylinder or two and go into limp home mode when it works out you've lost most of your coolant.
back on topic: one has to decide if the fans are going to be triggered by engine+coolant temps (e.g. sensor in/at thermostat housing) or coolant temp alone (sensor in one of the tanks).
in my case it's the former, as by the time the bottom tank's too hot, the hole shebang is close to cooking - and partly dictated by available holes to plug in sensors:
-one fan (suck thru) is on 100% except v.cold
-second fan (blow thru) on at hot
-third fan (blow thru) on at hot and/or aircon enabled
i figure if that doesn't work, its too fuken hot to drive so i'll drink beers instead.
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