Electric fan control idea. Looking for comments.

[Dan_Gyoba]

Okay, well, I was thinking about electric fans, and of course the problem is, how to control them. I've got an idea for this, and would like some feedback on the idea. I want to build an electric fan controller, which would trigger a relay to provide 12V to a set of electric fans.

In my car, I've got a Koyo radiator. This is relevant only because it's a 1JZ radiator, and therefore had the hole for the temp sender in the bottom. I don't know what the nature of this sender is, but I know that a 16mm by 1.25mm plug makes it perfectly suitable for 7M usage. I figure that I can't be the only one with something like this, so it's a decent basis to start from.

My thought was that putting in a temperature sending unit for an electric temp gauge in that location would give feedback on how the radiator is working. If the car is still cold, then the coolant at the bottom of the radiator would be cold. Even once the car warms up, if the car is moving fast enough, then the radiator should be working well enough without needing assistance from the fans, and the coolant at the bottom of the radiator should be at an acceptable temperature.

If we then use a Schmitt trigger to turn on the fans when the coolant at the bottom of the radiator gets hotter, and keep them on until it cools, this ought to be ideal, running the fans for the least amount of time needed in order to do an adequate job.

So, what do people think should be a good temperature to turn the fans on at, and when is it cool enough to turn them back off?

Temp at the water neck should remain at whatever the thermostat temp is, so 170~190 deg F. I figure that the temp at the bottom of the radiator should never exceed about 150 deg F under any circumstances (And was planning a "radiator over temp" output to trigger an idiot light which would warn the driver BEFORE the car overheats.)

I was figuring on drilling a 1/8" NPT tapped hole into a 16mm drain plug and putting in a standard temp sensor from an inexpensive water temp gauge.

Also, would the radiator need additional grounding? (The coolant should be a fairly good conductor to engine block ground, but is it good enough to rely on?) I think that the radiator mounts are insulated with rubber, so I don't think that there is a ground to the radiator tanks which can be counted on.

 

[jetjock]

The other flaws in your idea aside the radiator is isolated for a reason.

 

[Dan_Gyoba]

Well, given that coolant DOES conduct, it's not particularly well isolated, not to mention the contact possibilities of having a lot of otherwise bare aluminum exposed. Perhaps if you'd care to share what the reason for isolating the radiator is, and why it would be a bad idea to ground it?

I'd considered the possibilities of dislike metal corrosion, but considering that the head is aluminum this seems unlikely to be the issue. I know that in PC water cooling systems mixing copper and aluminum components causes problems, for example.

I'm also unclear as to what "other flaws" you speak of (This is why I was asking for comments.) It seems that Toyota thought that the temperature at the bottom of the radiator was a good place to check for fan control, as this is how the hydraulic fan for the 1JZ was controlled. As such, the practice should be sound enough.

I'm confident in my ability to design and build a control circuit which will turn on/off a relay from which the fan would be run based on feedback from that sensor.

 

[3p141592654]

You should use a two terminal sensor, like the one for the 7M ECU coolant sensor. I don't know what the 1JZ sensor looks like, but it seems likely it would be a two terminal style as well.

Do not ground the rad or heater core. If the rad is grounded, you have provided a current path through it that can result in electrolysis. The rad becomes an anode or receiver and corrosion ensues, as well as causing any stray voltage to use the coolant as the ground path.

 

[IBoughtASupra]

You have a Koyo and a 1JZ? If so, get a 2JZ-GE fan blade and 2JZ-GTE fan clutch and enjoy the good cooling.

If you have a 7M, a new 7M clutch and old blade will work.

What you gain in power from electric fans is now added stress to the alternator.

 

[KicknAsphlt]

Aside from the 'coolness factor' of building your own controller, there are already many fully-engineered controllers on the market. If it were as simple as wiring up a Schmitt-trigger and maybe an op-amp, then everyone would be doing it. I'm sure what everyone else has mentioned about providing a ground path through the radiator would apply as well, though I don't think that'd be an issue with a simple temp sensor/thermistor. Technically, the coolant is already 'grounded', seeing that it runs through a cast-iron block that has ground straps bolted to it. And unless you use nothing but deionized water in your cooling system, it's gonna 'conduct'. Just sayin'... Back to the controller though, it's going to be a little more complex than your initial post indicates; you need to think about the current draw of the fans on the controller and the initial 'hit' when they kick in, speed controls, etc.

 

[Poodles]

People arguing with jetjock :opcorn::

 

[ifyouaint1sturlast]

People arguing with jetjock :opcorn::

He's not arguing, JJ just denied it was a good idea and the OP asked why. I see why it's not a good idea to ground the radiator but I don't see why a dual pin sender wouldn't work.

I do agree with IBoughtASupra though, nothing works as good as a clutch fan it seems.

 

[mk3_7m]

I think my mate that worked on my car put on a similar fan controller you're talking about.

This is my old engine bay if you can see the copper wire going into the upper radiator hose that's connected to a swtich box connected to two 12 volt relays. I can set the fans to be on all day or when target temperture is reached and i think fan speed was also long down the track as well but he told me not to touch it as he already set it for me. I don't know much about it though, i never really asked him about it as i needed a car to get me to work already.

That was the old fan controller now he a put a new one when I got him to swap in the new radiator when I was attempting to fix this over heating issue I had. I can supply pics if needed.

 

[suprarx7nut]

Lol @ all the work people put into E-fans. :rofl: There are soooo many better ways to spend your time and money to make this car efficient.

 

[jetjock]

More like me not arguing with him. I don't much argue with anyone these days. Especially those who don't know what they don't know. Such people are difficult to reach. If they feel like I've given them bad info they can research it further themselves. In fact I'd prefer they do that. That said others in the thread covered it very well.

 

[Dan_Gyoba]

Hey, if I knew, then I wouldn't ask. I'm not intending to argue with anyone, just looking for info.

For the electrochemical corrosion in the radiator, as I said, it just seemed that it wouldn't matter because the coolant will already ground it, but if that is an issue, well, there's one.

Currently, my fan clutch is working fine, and I'm continuing to use it. This is just an idea for design. I was thinking of the temp probe in the bottom of the radiator anyway for a gauge, and as something that could let me know if my cooling system is being overwhelmed BEFORE the engine temperature starts to rise. Then came the idea that it could be used to control aux fans, and if those, then why not main fans?

And, rather than just proceed with building something, I figured that it wouldn't be a bad idea to ask. After all, that's how one learns.

For current control models, I have to wonder why people put the thermocouple probe in the upper radiator hose, since the coolant there SHOULD be at or very near the temperature at which the thermostat opens. It seems to me that turning on the electric fans after it gets hotter than that would be a bit late, since you're already overheating at that point, and turning them on AT that point just means that they're on whenever the T-stat is open, even if the car is at speed and doesn't need them.

So, grounding the radiator is out, but there are still ways to get a temp signal without introducing another ground. (Again, since Toyota did so, this must be the case.)

What do people think is a reasonable temperature range at the bottom of the radiator?

 

[GrimJack]

It seems to me that turning on the electric fans after it gets hotter than that would be a bit late, since you're already overheating at that point, and turning them on AT that point just means that they're on whenever the T-stat is open, even if the car is at speed and doesn't need them.

It's really a matter of setting your temp triggers to different points. In my car, the thermostat opens at ~75C, IIRC, and the fans come on at ~80 something. So if the car is warm, the thermostat is open, but if you're cruising in temps where the outside air isn't hot, it's possible for the cooling system to keep the coolant temp below the fan threshold.

Theoretically you could design a system to go the other way around, but electric fans have virtually zero drag on the system when they are off, so why not take advantage of that where you can?

 

[Enraged]

plus efans make working on the front of the motor a hell of a lot easier....

 

[jetjock]

Interesting you should point that out Dave. From reading posts I sometimes wonder how many here really understand the dynamics between thermostat, radiator and fan (electric or not) and the interaction of multiple setpoints. At times some seem confused about what each component even does.

 

[KicknAsphlt]

For current control models, I have to wonder why people put the thermocouple probe in the upper radiator hose, since the coolant there SHOULD be at or very near the temperature at which the thermostat opens. It seems to me that turning on the electric fans after it gets hotter than that would be a bit late, since you're already overheating at that point, and turning them on AT that point just means that they're on whenever the T-stat is open, even if the car is at speed and doesn't need them.

The reason they reference the temps at the radiator hose is because you don't want to cool the system off enough to close the thermostat. By using the actual engine coolant temp and not the post-radiator temp, they can keep that from happening a lot easier. This is how pretty much every automaker designs their systems and is perfectly fine...you just set your on/off setpoints where you want above the T-stat open temp.

 

[Poodles]

The main reason they make kits to add a temp sensor to the upper radiator hose is because it's easy to do, not because it's best to do. OEM's use sensors on both sides of the t-stat for varying reasons.

 

[IJ.]

Did a LOT of testing when I had the Fans hooked up to the MoTeC and found you needed a 5>8c run up if you were to have any hope of catching it before the temp ran away, also found in a Mk3 it's better to have them slowly moving at cruise so the car can run on the T Stat.

Another point was the MASSIVE current inrush if you start them at 100%, I had 4x fans on my car and they came close to maxxing out the 140a alternator if started all at once so I PWM'd them then ramped them in.