Electric fan placement

[JelmerPatrol]

I want to place a electric fan on my L28. There is a spare plug in the thermostat housing. Can I use this hole for a thermo switch? Or do I need to place it somewhere else?

[Guest Flauski]

interested to know the answer to this also....

[ozconnection]

I've just recently changed over to an electric fan triggered by a thermostatic temperature switch.

 

The switch is a simple normally open device that triggers at 70 degrees celcius. I use it to trigger a relay setup. (I don't run the 10-15 amps drawn by the fan through the switch). I put this switch at the top of the fins on the radiator on the side away from the radiator hose, so when the thermostat opens and hot coolant passes through that area, the electric fan is triggered. It has a mounting tab so I could use two 1/8th thick but about 50 mm long threaded bolts to pass through the radiator fins to mount it securely. Those bolts were sourced from the local hardware store for only a dollar or so. The switch was purchased from an electronics (Jaycar Electronics) store for US$5.00. Altogether, very cheap, simple and effective.

 

This setup works really well and has proven itself to be very reliable in the hot summer months we have here at the moment. I find that the fan switches off as I drive and switches on again if I drive at a low speed or stop at an intersection etc. When I move off, the fan switches off again, so long as I drive above 25 mph or 40 km/h. It cycles on and off when idling for extended periods, running for a minute or two, then off for 20-30 seconds, then on again. Exactly like a late model car. Once to operating temperature, the temperature needle is very stable. Highly recommended.

 

Cheers!

[Zmanco]

I installed a GM coolant sensor in the port on the side of a 73 thermostat housing where the coolant from the carbs/manifold returns. I had to use a brass adapter to get the threads to match and it worked great for a few years.

 

On my turbo motor I did the #5/6 cylinder cooling mod so used that side port for the return. But on the turbo thermostat housing there was another undrilled port just next to the factory sensor facing towards the radiator that I drilled and tapped. It too works fine.

[ozconnection]

I had a long, hard look at what I wanted my setup to be able to do.

 

Several companies sell quite sophisticated setups that will allow the user to define the temperature setting at which the fan switches on/off. Some are reasonably priced, some aren't.

 

The 'problem' I see with using the thermostat housing as the temperature pick up point is the limited range of temperatures seen there once the engine is up to operating temperature compared to the temps seen at the radiator (verified by a laser heat gun). Using this area for your sensing, I believe your fan will be on virtually all the time and I also believe that that situation isn't what's needed.

 

With the temp sensor on the radiator, the coolant's temperature will determine the switching of the fan in a more representative manner.

 

The range of variables I see are:

Start up-hot and cold

Idling

cruising-low speed and high speed

hard driving-towing,draging,drafting

 

Depending on the style of driving (cruising, speeding), the ambient temperatures (ie summer/winter) and the volume of airflow through the radiator (ie low speed driving, high speed driving, drafting) the temperature of the coolant through the radiator will vary. Why run the electric fan when the engines coolant doesn't require any further cooling? Or, on the other hand, will switch on if the demands of driving require it.

 

I know, for example, that there are temperature switches for some Nissans that screw into the radiator like I suggest to control the switching of the electric fans.

 

Don't get me wrong Zmanco, your approach obviously worked well for you as does my setup for me. I do think that there may be some advantages in sensing and switching the fan from the radiator though.

 

Good luck.

[Zmanco]

The 'problem' I see with using the thermostat housing as the temperature pick up point is the limited range of temperatures seen there once the engine is up to operating temperature compared to the temps seen at the radiator (verified by a laser heat gun). Using this area for your sensing, I believe your fan will be on virtually all the time and I also believe that that situation isn't what's needed.

I would argue the temp of the coolant at the bottom of the thermostat is more representative of the temp in the engine (especially the head which is what's key to controlling detonation) than the temp in the radiator. The key is to set the "on" temp to something a few degrees hotter than you're likely to see on a warm day at cruising speeds. In my case the only time the fans turn on are during extended idle periods, and on really warm track days.

 

With the temp sensor on the radiator, the coolant's temperature will determine the switching of the fan in a more representative manner.

Representative of what? Remember, the factory mounted the clt temp sensor in the bottom of the thermostat housing as well. They could have mounted it anywhere.

 

Don't get me wrong Zmanco, your approach obviously worked well for you as does my setup for me. I do think that there may be some advantages in sensing and switching the fan from the radiator though.

I don't think there's anything wrong with mounting the sensor in the radiator fins (aside from it being difficult to get it stay put over time). However, I think those products are targeted more at the casual hobbyist who doesn't want to open up the cooling system to make a modification. In short, they're usually easier and faster to install. I ran with one of those systems from Hayden for a while and it worked well-enough. But I can't see how that location is better at determining the engine's cooling temp than the factory location at the bottom side of the thermostat.

[ozconnection]

I would argue the temp of the coolant at the bottom of the thermostat is more representative of the temp in the engine (especially the head which is what's key to controlling detonation) than the temp in the radiator. The key is to set the "on" temp to something a few degrees hotter than you're likely to see on a warm day at cruising speeds. In my case the only time the fans turn on are during extended idle periods, and on really warm track days.

 

 

Representative of what? Remember, the factory mounted the clt temp sensor in the bottom of the thermostat housing as well. They could have mounted it anywhere.

 

 

I don't think there's anything wrong with mounting the sensor in the radiator fins (aside from it being difficult to get it stay put over time). However, I think those products are targeted more at the casual hobbyist who doesn't want to open up the cooling system to make a modification. In short, they're usually easier and faster to install. I ran with one of those systems from Hayden for a while and it worked well-enough. But I can't see how that location is better at determining the engine's cooling temp than the factory location at the bottom side of the thermostat.

 

Gee, I thought I explained my setup very clearly.

 

The exploration into the world of L series engine cooling has been done to death in several very recent threads and although I'm no expert on the subject, I've tried to be open minded, offer alternate solutions and I've genuinely learn't heaps along the way.

 

The radiator is an excellent point of reference for temperature triggering for all the reasons I've already mentioned.

Edited February 24, 2010 by ozconnection

[RIP260Z]

Chaps,

I see where you are coming from. Can I just add to the thought processes (whether right or wrongly)

 

A factory option on the 280z (North American spec, as seen on the parts microfiche) the electric fan takes its thermostat reading from an in-line housing on the radiator hose going back into the engine.. I think (though I have no experience of) the same thing is set up on the 300zx?

 

Posted my Zmanco (I tried quoting)

But I can't see how that location is better at determining the engine's cooling temp than the factory location at the bottom side of the thermostat.

 

Is this not just where the factory design takes the engine temp, and goes to the gauge so the driver to see, and is not connected to an electric fan, though maybe to an ECU? Surely to determine the engine's cooling temp, would suggest after the radiator (its had its cooling)?

 

 

So, would the thinking be it is preferable to have the coolant going back into the engine at the "correct operating temp" (whatever that is) after any cooling has been done by the radiator/air flow, as in the OEM option?

[Zmanco]

I want to place a electric fan on my L28. There is a spare plug in the thermostat housing. Can I use this hole for a thermo switch? Or do I need to place it somewhere else?

Guys, I think we lost sight of the OP's question. The short answer is "yes", you can use the spare plug on the t-stat. You can also place it between the radiator fins.

 

This discussion is morphing into "where is the best place to locate the temp sensor" and that topic has been discussed (flogged?) in great detail in other threads, so I'm going to bow out of it here.

[JelmerPatrol]

Well, it worked fine with the temp switch in the thermostat housing. I put it all together and it workes good.