Radiator Fan activation temperature

[redpoint5]

Originally Posted by stovie

does anyone know how well a "cylindrical radiator would work?

so to summarize i'm talking about trying to run the area of a 1.5" pipe around 4-5 other pipes in order to increase the coolants over all time in the "radiator" from 24" to as high as 6-8' or more.

It would provide more cooling capacity, but I'm unsure how much. Stock radiators already have a heck of a lot of surface area, so I'd be doubtful that increasing the run length would improve cooling efficiency by much.

The #1 thing you can do to increase cooling efficiency is to seal the gap between the grill opening and the front of the radiator. There is usually a good 1" or more gap between grill opening and the cooling fins, so air is allowed to move around the radiator instead of through it.

I tend to think the gap exists on purpose. If the grill were to get completely blocked, perhaps due to snow, the fans would still be able to pull air through the radiator, albeit much less efficiently. If you seal the gap, the fans must draw air through the grill opening.

[Occasionally6]

Originally Posted by BrandonMods

What would you recommend for the voltage source? I might be able to get my hands on a DC power supply but there are no guarantees on that one. Any other ideas would be appreciated.

Anything that results in a regulated 5V will work. At various times I have used: the USB adaptor, both wall plug and cigarette lighter ("12V") powered; a superfluous non-USB phone charger with the tip modified, wall plug powered; a bespoke, "12V" powered, 7805 based regulator circuit on perf. board with noise filtering (a web search will bring up any number of schematics for these); a spare ECU with just the power (plural) and ground wires connected, using one of the 5V reference outputs.

"12V" came from a car cigarette lighter, an SLA battery or a DC bench power supply.

You do need to be careful with the polarity with all of them.

Originally Posted by MobilOne

Why not just put a small current 12v bulb in parallel with the fan motor? Why make it complicated?

Careful with incandescent bulbs as they can draw a significant amount of current. On the fan side of the relay it is probably a tolerable fraction of the motor current. An LED (and resistor) is just as easy and will draw only a tiny amount of current, definitely a negligible current relative to the fan. (Don't even consider an incandescent bulb on the switching side of the relay.)

[BrandonMods]

Originally Posted by Occasionally6

If you want, you can calibrate sensor voltage against an actual temperature with the sensor removed from the engine or a junkyard sensor. Put it in water brought to the boil or cooling from boiling, with a thermometer to read the actual temperature. Then plot the temps with the corresponding voltage.

When doing this to measure the actual voltage corresponding to the temperature I would just measure the voltage drop across the sensor correct?

[BrandonMods]

Originally Posted by Occasionally6

Put it in water brought to the boil or cooling from boiling, with a thermometer to read the actual temperature.

Also shouldn't I just use coolant and apply heat to it since water boils at 212F. If the fan activation temp is above that then I would only have reference voltages up to 212F.

[redpoint5]

This whole thread could be answered with a $9 ELM237 OBDII bluetooth adapter and a free app called Torque.

You can then read the temps directly and see when the cooling fans turn on.

There are more expensive and complicated ways to keep tabs on things, but this would be the cheapest/easiest/most accurate way.

[Occasionally6]

Originally Posted by BrandonMods

When doing this to measure the actual voltage corresponding to the temperature I would just measure the voltage drop across the sensor correct?

Yep. Also, check (measure) the reference voltage in the car and what you are using match. The reference voltage is what is across the CTS connector with the sensor disconnected.

Originally Posted by BrandonMods

Also shouldn't I just use coolant and apply heat to it since water boils at 212F. If the fan activation temp is above that then I would only have reference voltages up to 212F.

The sensor voltage is pretty linear wrt temp. The activation temp. for the first fan speed won't be much above 100c (212F) anyway. You can extrapolate the little bit of temp. that is above (the voltage should be lower) on your plot.

[Occasionally6]

Originally Posted by redpoint5

This whole thread could be answered with a $9 ELM237 OBDII bluetooth adapter and a free app called Torque.

You can then read the temps directly and see when the cooling fans turn on.

There are more expensive and complicated ways to keep tabs on things, but this would be the cheapest/easiest/most accurate way.

Maybe. I could do the voltage testing at $0.00, out of the parts box. Without that parts box, ^ probably is the better way.

[BrandonMods]

I was just looking at the fuse block and there are; 2 cooling fan K3 micro relays, 1 u-micro relay K7, 2 HC- cooling fan relays one is K2 and K1. I'm unsure what the K #s stand for anyone know? Also i'm unsure what the U, and HC prefix for the relays are.

[BrandonMods]

Okay so I have done some digging around and it seems that HC stands for high current. I'm figuring that those two relays must have something to do with the fans speed and so only open when the fan must spin faster as they can allow up to 120A based upon the rating from what I have read. I'm still unsure of what the "U" relay does for the cooling fan. There is also two general "micro relays" and then there is the matter of the K1, K2, K3, and K7 delineations as well. So figuring in i want to prevent the fan from coming on at all I would want to target the relay that controls the lowest fan speed. Now I just need to figure out which one of them controls it right?