Best place to install coolant temp sensor for e-fan?

[ChrisOFNA]

Hey guys,

I just bought an e-fan and electric thermostat setup for my 93 240 to get rid of the clutch fan of power-robbing. Where would be the best place to tap and install the sensor? It has a 3/8" NPT sensor.

For those who are wondering which kit I bought:
http://www.ebay.com/itm/290765225695...84.m1439.l2649

[olov]

i was told to put my saab sensor and T pipe in the lower rad hose. but maybe someone has a better place for your application

[FattMatt805]

Should be in the top hose or in a coolant passage in the head

[Captain Bondo]

Originally Posted by FattMatt805

Should be in the top hose or in a coolant passage in the head

Always in the lower hose (outlet). You don't switch the fan on because the coolant entering the rad is hot. Of course it's hot, it just came out of the cylinder head. You switch the fan on when the coolant leaving the rad (entering the motor) starts to get too hot. That means you need to increase airflow through the rad.

Isn't the OEM Volvo one in the pass side top of radiator?

[apachechef]

Originally Posted by Captain Bondo

Always in the lower hose (outlet). You don't switch the fan on because the coolant entering the rad is hot. Of course it's hot, it just came out of the cylinder head. You switch the fan on when the coolant leaving the rad (entering the motor) starts to get too hot. That means you need to increase airflow through the rad.

I did this and it worked great.
Remember to grab the SAAB sensor from the radiator to replace the one in the SAAB t-Pipe if you are getting it from the junkyard.

[Jorn]

Originally Posted by smokeyfan1000

Isn't the OEM Volvo one in the pass side top of radiator?

That's where I have mine, temperature gauge always stays steady in the middle.

[Captain Bondo]

Originally Posted by smokeyfan1000

Isn't the OEM Volvo one in the pass side top of radiator?

Same difference. That is the cold side of the radiator. The outlet side. That's more important than top/bottom. Lower is better though because most sensors won't read steam properly. So, if you're low on coolant and a senor mounted up high is not submerged, your fan won't switch reliably.

[badvlvo]

I run mine in the upper hose on my current car, and on many in the past. Works just fine for me.
The sensor in the lower hose will read coolant that has already been cooled by the radiation, not necessarily indicative of actual engine temp.
OEM has temp sensors in the t-stat housing or head on almost every application I can think of, indicating actual coolant temp in the engine before being cooled by the radiator.

Or you could put it in the lower hose.

[Kjets On a Plane]

Volvo puts it on the cold side of the radiator (passenger side) near the top switched on at the ragged edge of meltdown(regina cars), or via the LH ECU temp sensor in the cylinder head, also switched on at the ragged edge of meltdown, soon to be immersed in air with slight coolant loss or boil over, melting holes in the head. Both are PERFECT for longevity and heavier use!

Porsche 944 have a little cooler switch for guys that want to use the radiator temp switch dealie.

Or the SAAB story thingamajig

[Captain Bondo]

Originally Posted by badvlvo

I run mine in the upper hose on my current car, and on many in the past. Works just fine for me.
The sensor in the lower hose will read coolant that has already been cooled by the radiation, not necessarily indicative of actual engine temp.
OEM has temp sensors in the t-stat housing or head on almost every application I can think of, indicating actual coolant temp in the engine before being cooled by the radiator.

Or you could put it in the lower hose.

That's because the fuel injection systems need to know cylinder head temp. The primary purpose of that sensor is for fuel control not fan control.

With any heat exchanger, it is the OUTLET temp you are interested in, not the inlet temp. It's just common sense. Yes some system use cylinder head temp and a few other things to control fan function (when the head temp is 10 or 15 degrees hotter than the tstat or so, but that's just a guess) , but the best way is with a sensor that is actually measuring the outlet temp.

[Kjets On a Plane]

Would it not be reasonable to conclude that, there could arise the situation, where, briefly, the top end exceeds the mechanical t-stat temp before the switch kicks the fan on?

Further, lower temp water from the bottom radiator hose might be required to be supplied than the temp that the switch turns off at over time under load to avoid an overheat i'd think...you get a delayed reaction and continue to apply load over time and slow (or alter) the rate of circulation?

It probably works, but it is in my nature to nitpick.

[Captain Bondo]

Originally Posted by 945ti

Would it not be reasonable to conclude that, there could arise the situation, where, briefly, the top end exceeds the mechanical t-stat temp before the switch kicks the fan on?

Further, lower temp water from the bottom radiator hose might be required to be supplied than the temp that the switch turns on at over time under load to avoid an overheat i'd think...

Yeah exactly. That's the sort of scenario I was implying when i mentioned the ecu is really just "guessing" when the fan should come on. It's not ideal to use the head sensor. OEMS do it because 1 sensor is cheaper than 2 and it works "most of the time", especially on stock stuff.


What I do on my own projects (programmable EMS) is I use both. I run the fan on low speed with the EMS based on head temp for the most part. I run a t-stat temp I'm comfortable with, and switch the fan on 5 degree later. I also have a temp switch on the cold side wired to the high speed on the fan relay. If something weird happens or the ecu output flakes or I put a wrong number in, the rad temp switch works as a backup. Generally the rad switch never kicks on, but I keep it there because as you say, using a head mounted sensor is far from idiot proof.

If I could only keep one or the other I'd keep the switch in the cold side. It is worth noting that the cold side switch point ought to be ~20 degrees or more lower than the t stat temp.

[Kjets On a Plane]

I call my solution a new fan clutch, or new fluid in it depending on condition. *shrug* Works for me. Very progressive response, fail safe switch for higher quality pusher fan.

[Captain Bondo]

Originally Posted by 945ti

I call my solution a new fan clutch, or new fluid in it depending on condition. *shrug* Works for me. Very progressive response, fail safe switch for higher quality pusher fan.

That's perfectly fine, but not relevant to most engines designed after about 1992. I saw no reason to retrofit a clutch fan to my T6 motor for example.

Also, I've seen more blown up/worn out clutch fans than I have failed electric ones. There are many parts in a car that are less reliable than an electric fan. Its not exactly bleeding edge technology, they have the bugs worked out.

[Kjets On a Plane]

Depends on the intended use.
DC motors and fan blades have been around a long time. Variable speed controllers for such motors digitally controlled, maybe not.
The fan clutch fluid shears and shears no more over time, yes.
Dragging a load over a mountain, it gets a fan clutch.
Doing such even with the much larger radiator, larger alt and electric cooling fan the cars got is not a pretty sight on a warm day with the a/c on, even with not that heavy of a load. They tried, and really re-arranged the car for it.
Doing so with the freshened clutch fan? No issues.

If you change the flow of the water and load over time, I suspect that even in the lower hose, might be too reactive, and better than nothing, but not necessarily appropriate for airflow required.

I'll definitely put an E-fan on the new work trucks, complete with 6hp alternator, variable speed fan controller, and radiator the size of a house! Or just leave it stuck to the front of a giant engine...*shrug* Or hydraulic drive.

Originally Posted by Captain Bondo

Same difference. That is the cold side of the radiator. The outlet side. That's more important than top/bottom. Lower is better though because most sensors won't read steam properly. So, if you're low on coolant and a senor mounted up high is not submerged, your fan won't switch reliably.

Aahh yes. I agree.

The OEM WT gauge doesn't read steam temp very well. I discovered that on an engine overheat due to cut heater hose.

Thefore any other sender won't either. Sender has to be *submersed* in a liquid to register

OEM temp gauge in Int Clstr never read hot, untill I added some water (summertime) when I got to station.

[badvlvo]

Originally Posted by Captain Bondo

That's because the fuel injection systems need to know cylinder head temp. The primary purpose of that sensor is for fuel control not fan control.

With any heat exchanger, it is the OUTLET temp you are interested in, not the inlet temp. It's just common sense. Yes some system use cylinder head temp and a few other things to control fan function (when the head temp is 10 or 15 degrees hotter than the tstat or so, but that's just a guess) , but the best way is with a sensor that is actually measuring the outlet temp.

Then explain to me why countless OEM's use a coolant temp sensor and a fan switch separately?

You go ahead and control your radiator temp, I'll control my engine temp.

[Kjets On a Plane]

He just did. Cheaper to use one sensor. It lasts the warranty and isn't double redundant. It's a car built cheap in the modern world, not an airplane. What do they care if it gets a little hiccup or airbubble or sensor has a screwup? Catastrophic engine meltdown is not their problem 1 second and one mile out of warranty.

I'm shamelessly trolling on going to all the trouble to install an electric cooling fan. John Lane's car works fine with the clutch fan *shrug*.

Originally Posted by 945ti

He just did. Cheaper to use one sensor. It lasts the warranty and isn't double redundant. It's a car built cheap in the modern world, not an airplane. What do they care if it gets a little hiccup or airbubble or sensor has a screwup? Catastrophic engine meltdown is not their problem 1 second and one mile out of warranty.

I'm shamelessly trolling on going to all the trouble to install an electric cooling fan. John Lane's car works fine with the clutch fan *shrug*.

Seems to me, the extra voltage/amps required to run e fan, makes alt work harder. And we know what turns the alt.

Ever notice how the engine slows a second when you turn on your headlights? Think about it.

[apachechef]

Originally Posted by smokeyfan1000

Seems to me, the extra voltage/amps required to run e fan, makes alt work harder. And we know what turns the alt.

Ever notice how the engine slows a second when you turn on your headlights? Think about it.

uh, Alt is not working harder when the fan is off, buddy. engine driven fan is not free.
but thanks for pointing out how this new fangled 'lectricity works.
E-fan can run after engine shut down
E-fan is quiet
faster warm up
blah blah blah
deadhorse.

[ChrisOFNA]

I'll have to find the article later, I think hot rod magazine did a clutch fan vs flex fan vs e fan on all the time dyno test. From what I got from here probably somewhere near the lower radiator hose?

[doucheNozzle]

Originally Posted by Jorn

That's where I have mine, temperature gauge always stays steady in the middle.

That's because you have a compensator board.

Originally Posted by scottyd

That's because you have a compensator board.

+1 After removing the comp board and using the IPD kit, I notice the temp gauge having a more sweepin range of temps. Especially due to changes in ambient temperatures

Originally Posted by apachechef

uh, Alt is not working harder when the fan is off, buddy. engine driven fan is not free.
but thanks for pointing out how this new fangled 'lectricity works.
E-fan can run after engine shut down
E-fan is quiet
faster warm up
blah blah blah
deadhorse.

Engine isn't working any harder when the engine driven fan's clutch isn't engaged . Redblock fan /Wp belts rarely/ *if ever* fail

When the efan takes a permanent vacation,(and they do) engine damage is likely to occur.

I like engine driven fan for that reason.