Cooling Fan Sensor

Where is the best place to screw in a Cooling Fan Sensor which will control an elecric fan mounted to the radiator. Possibilities are the side of the engine block where there is a drain plug. In the end of the cylinder head where there is a plugged hole, or the intake manifold where there are several possibilties. My concern with the intake manifold is it is very near the thermostat. I've read that the sensor should be placed near the outlet of the radiator (bottom) where the cooler water is coming out so the fan doesn't constantly run. Engine is a 3.4 Chevy V6. Thanks!

I think I'd be contemplating something like this unless one of your options is obviously right in the coolant flow from the radiator.

I got lucky. The Aspen/Volare radiator I fitted to the Valiant happens to have two bungs for sensors, one passenger side and one driver side. Right now I'm using the one nearest the inlet. It's nice to have options!

The best place is in the radiator end tank on the exit side. The second best place is in line with that hose via the adapter the awesome Ransom linked you to, a very distant third is one of those probe sensors that go through the radiator fins. Reading the water temps in the block or head won't tell you when the radiator needs to be cooled.

I really like the VW rabbit fan switch.

It is sturdy, avaliable in a wide range of on/off temps, and even though it is supposed to switch a relay is stout enough to work without one on a 15 amp load. On brass radiators I braze/solder in a bung harvested from an old VW radiator. For aluminum radiators I actually bought the 20mm tap to make my own bungs and weld them in.

If you absolutlely have to install it on the motor put it as close to the water pump outlet as you can get it. That should be hot water straight from the radiator. It will still cycle your rad fan when the thermostat is closed and it doesn't need to be running though.

GM put the oem temp sensor in the intake manifold next to the thermostat housing- i think they knew what they were doing.

volvo mounted them in the radiator or with a T type thing ransom posted... biggest thing is finding the proper temp sensor for kicking the fan on/off at the right times.

novaderrik wrote: GM put the oem temp sensor in the intake manifold next to the thermostat housing- i think they knew what they were doing.

GM also went bankrupt. I'm not so sure they always knew what they were doing.

it's ok as long as it's not hot out and you don't plan to stop going 45mph. Ever.

put the sensor in the radiator, if possible.

Most of the cars I have owned that had electric fans, had the sensor on the "cool" side of the radiator. This includes a Fiat, Hyundai, and BMW.

The saab has it in the middle of the "hot" hose

princess wrote: i just wanna ask if is it ok to run a car without radiator cooling fan??what will happen??? does it may affect any car parts?thanks

Nonononono.

Car parts affected include heads & blocks (think of them as upper & lower ventricles of the heart). All that aluminum stuff on my imports would melt, but even the cast iron on your Chevy would warp. Bad news. If worst comes to worst, bypass the sensor with a switch inside the car, and turn on the fan yourself when the temp gauge gets close to the red. Overheating an engine usually kills it..and bends the bigger pieces so much that a rebuild is not an option.

princess wrote: i just wanna ask if is it ok to run a car without radiator cooling fan??what will happen??? does it may affect any car parts?thanks

I went several months on my Ti before I discovered that it had no sensor (removed by PO). Most of my driving is steady state with a few quick lights. It was not until I went to Philiadelphia and got stuck in traffic did I discover the that fan was not working.

I am not saying you should do it.. just that it can be done for a short while..

Modern Temp gages have three settings. Cold, Normal, and Toasty!

mad_machine wrote: Modern Temp gages have three settings. Cold, Normal, and Toasty!

(Sorry, you post reminded me of the guy from Mortal Kombat who pops up and squeals "TOASTY!" randomly)

Anyways, back OT, my jury-rigged cooling system solution for the turbo FC uses a tee like this:

...on the hose between the radiator and thermostat. I'm adding a VW cooling fan sensor to it that has two speeds: low once the temp. reaches ~185degF, and high at ~215degF. The fan is from a 1st. gen. Ford Taurus, which moves approx. one metric arseton of air over the Koyorad double-pass radiator. We rotards take our cooling seriously.

princess wrote: i just wanna ask if is it ok to run a car without radiator cooling fan??what will happen??? does it may affect any car parts?thanks

depends. i was not aware that trolls had cars.

i use an adapter like ransom posted on my impala, seems to work fine. they are super freaking cheap on ebay. like 10 bux cheap.

I wired one in to one of our cars to be triggered by engine rpm. The reason for this was drivers coming into the pits were forgetting to turn it on. So I set it come on under 2000 rpm. Worked so well I set one up in my Porsche. This way at idle or in traffic the fan comes on. I put a switch in the circuit so I can manually over ride it to either off or on all the time as well as RPM controlled (simple 3 positions switch and a couple of relays). I then wired the second fan (the one Porsche uses when AC is called for) to a switch that is a simple on off for complete manual control and as a backup if I have a failure in the first / primary one. Works great.

Edited for spelling

Where you put the sensor also depends on what temperature it is set to come on at. If it is set to come on at, say 215 degrees, then I would put it in the intake/head near the thermostat or in the upper hose. If it was set to come on at 170, then the cool side of the radiator would work. All the cars I have had all had the sensor in the hot side FWIW.

dean1484 wrote: I wired one in to one of our cars to be triggered by engin rpm. The reason for this was drivers commingle in to the pits were forgetting to turn it on. So I set it ti come on under 2000 rpm. Worked so well I see one up in my Porsche. This way at idle or in traffic the fan comes on. I put a switch in the circus so I can manually over ride it to either off or kn all the time. I then wired the second fan to athe seitch for complete manual control. Works great.

that's a damn good idea

81cpcamaro wrote: Where you put the sensor also depends on what temperature it is set to come on at. If it is set to come on at, say 215 degrees, then I would put it in the intake/head near the thermostat or in the upper hose. If it was set to come on at 170, then the cool side of the radiator would work. All the cars I have had all had the sensor in the hot side FWIW.

I was just going to say that.

princess wrote: i just wanna ask if is it ok to run a car without radiator cooling fan??what will happen??? does it may affect any car parts?thanks

My cooling fan sensor is the driver's eyeball method.

Driving around, I never have to switch the fans on unless I'm sitting still for more than five minutes. Anything over about 20mph is plenty airflow to keep the engine cool.

If I'm sitting still but don't expect to get moving soon, I'll just shut the engine off rather than screw around with turning the fan on and manually holding the engine idle up. I have two dual-speed fans, two switches, about 25-30a draw on each switch. Turning the fans on can make the car stall from the alternator load. (When I'm engaged in motorsports activities, I turn the idle speed up)

The first engine swap I did, drove around for months in the summer with no fan. Worked just fine, just keep an eye on the coolant temp gauge and stay out of situations where you're stopped a lot.

I drove lot of my older cars without a fan. If the heat got too high I just turned on the heater for a little while.

I used something very much like this:

http://www.amazon.com/Hayden-Automotive-3653-Adjustable-Thermostatic/dp/B000C39C6I/ref=sr_1_2?s=automotive&ie=UTF8&qid=1332027733&sr=1-2

Works great for me and you don't have to figure out how to get into the coolant.

BTW, your local NAPA will have a big book of sensors that shows the thread size, the trigger temperature and even the electrical connection on top. Really useful.

I've considered putting in a manual override for the cooling fans on one or two of my cars. On a racer, I've set it up so that the driver can turn the fans on early, but the sensor will always be able to trigger them as well. On the old Land Rover, I've looked at putting in an off switch so that it won't throw so much water around the engine bay while fording deep water. However, in that case I would have a very large red light indicating that the fan was off. In no case would I trust myself to have sole control of the fan. You only have to screw up once.