Disappointed fan install job, need help/ answers.

You could also wire in an on-off switch or buy a bimetallic switch and epoxy it to your radiator. There was a thread on Thumpertalk adding the fan and a temp switch (in '05 I think). Do a search if interested. temp switches are available through Grainger or McMaster

Ach, that makes it a bit more difficult! Bear in mind though that the cold resistance of the sensor is in excess of 1300 ohms so the draw would be at most around 10mA (depending on the resistance of the relay it could be rather less). Theoretically a 6Ahr battery would be flattened in ummm... 600 hours, so you could get away with bunging a trickle charger on the battery if you were't riding it for a few days. Also the fan may run for a time after the engine stops, but possibly not long once the correct cutoff temp is set.
As has been stated, you could fit a manual switch, or an AC relay switched by the bike's clipped AC lighting circuit, which is only live when the engine is running. (I'm assuming your bike has an AC lighting circuit - I haven't found a wiring diagram for one. Can you link me to one?)

A 12V AC relay might be a little hard to find, but an ordinary DC automotive one could be pressed into service with the addition of a couple of diodes and a capacitor - that may sound a little daunting if you don't have any electonics experience but I could try to walk you through it.

Sorry for the delayed response, I've been away a week.


Also, maybe I used a poor choice of words when I thanked active members but it sure wasn't sarcasm. It was a genuine thanks. And I was hoping maybe some one with even more knowledge on how the fan works might add more.

The bikes a '07 and because it came with no fan I'm assuming it's a non-Euro model.

Not sure,.. by FB, you mean feedback? So do you think there's something I can ad to my circuit to manipulate the sensor to make it operate the fan the way it should? ( Maybe just add resistance?)

Dave

My slow response was due to a sorely needed week vacation. Now I'm back and ready.

7point62:

Thanks for the offer but yes, thats too daunting for me.

Over in my origional thread Coffee mentioned my sensors a thermister and maybe as you said just getting the right resistance in the circuit will cure all. I'll address any possible battery load issues later...maybe with a switch.

Dave

you may want a T piece "in hose" type temp sensor... pm me if you want the guys details who makes these... husky owner of 10yrs and pretty top bloke too ! he is here in oz but i reckon thats not a problem !

I bought the temp sensor my dealer had in stock, mostly just because I was so pleased he had one, but I remember it's part # didn't match exactly the # from the online fitche I was using. Now, I'm sorry to say I can't be sure what fitche I was using. ( I need to get it all straight ... maybe some Husky's use a true temp switch with the same thread size).

Anyway, I'm using a OEM part because I was shooting for automatic temp control..... sensed in the head... jst like OEM. I went to a lot of effort ... pulled the motor, pulled the head, drilled,threaded and surface milled the spot it goes. Ten times the effort of glueing it to the radiator or putting it in a hose fitting.
I'm really hoping it wasn't all for naught and I'm not to the point of giving up. That said, if it must be, I'll add a hose tee and buy a Grainger temp switch.

Today I tried adding ressistance inline with the sensor. With 250 ohm added, the fan never came on when my Trail-Tech unit saw 235*. Nor would it come on with 100 ohms. The 250 and 100 in parallel also didn't start the fan at a desired temp, (I forget the formula but I know it's less than 100 total). No more ressistors so tomorrow I'll use a potentiometer.

Last, my bad...pilots the 42 and the air jets 85 as Coffee suggested.

Dave

formula is 1/R1 + 1/R2 + 1/Rx etc = 1/R total

e.g.

1/250 + 1/100 = 0.004 + 0.01 = 0.014

1/0.014 = 71 Ohms.

Note that you can add any number of resistors in parallel and the formula will work (but the potentiometer will be easier on the brain!)

Hope you work it out mate.

Alright, 50 Ohms will work. I got a Radio Shack low wattage 47 Ohm resistor and stuck it in the loop. The fan kicks on pretty consistently right around 210* F on temp rise. Unfortunately it doesn't turn off by itself when the temp drops to, say 165-170* by riding fast. And beyond that, it continues to run upwards of 10-15 minutes after the bike off sitting in the garage. I guess once the relay's contacts close on temp rise it takes a substantial voltage drop at the coil to get them to open back up. With the manual switch I also have in the loop I can "cycle the power" to the relay. So long as it has cooled down enough the fan won't restart until the next "overheating" event.

Not the ultimate set-up but at least I don't have to rely on my brain to realize the bikes overheating and to turn on the fan.

I wonder if trying a different relay would help. Mine has about 83ohm coil resistance... don't want to overload the Husky thermistor.

Dave

I don't know anything about how this is wired but it's common for things which switch over at a given point such as a fixed temperature to have some "hysteresis" built into the system. Say the relay's designed to close when the temp rises past 210F, it won't open until the temp drops to something lower than that, say 200F. Otherwise, if it was designed to both open and close at the same temp and the coolant happened to be at that temp, the relay could be constantly chattering (repeatedly opening and closing) which wouldn't do it or the fan any good. The fact that you can manually break the circuit once it's cooled off a little and it then doesn't restart the fan is what you'd expect with hysteresis, as it's below the trigger point for turning on.

Having said that, even if there is something in this system which is meant to provide hysteresis I'd expect the fan to go off before the temp dropped to 170F so maybe there's something else going on...

I'm not sure I've managed to keep track of exactly what configuration you've ended up with, but IIRC you have a non standard temperature sensor with the 50ohm resistor in series to get the turn-on point at the right temperature and this is connected into an electronic control unit? If so, the sensor obviously has less resistance than the standard one at a given temperature which means that when the temperature changes, the change in resistance of the circuit as a whole will not be the same as it would if you just had the standard sensor in circuit. As an extreme example, if the sensor's resistance dropped to zero you'd still have a resistance of 50ohm due to the fixed resistor, rather than the zero the control unit would expect at that temp. This means that the profile of the circuit as a whole (i.e. how the resistance changes with temperature) is not the same as it would be for the sensor alone, even assuming the sensor itself has the same profile as the standard one.

If that is the case, by selecting the fixed resistor to the right value you'll be able to get the current system to match the standard one at a single temperature (as you did to set the turn-on point) but not over a range of temperatures, so it may not be possible to get it to also turn off at the temperature you want. It might be possible to come up with a way to fix that but it could be tricky so I guess the next question is whether you can live with it as it is?

Of course, I could be talking complete *%$$*$&&.

Not at all. Thanks for the input. your assesment of my circuit is close but not just right.
I'm using the OEM Husky temp sensor,(thermister), and also the Husky relay it triggers. The sensor, the relay's coil and my added 50ohm resister are simply in a loop with the 12vdc battery supplying power. The 50 ohms is there to get the relay to close at 210*.

These two Husky parts are from a 2008 TE/TXC/SMR 250/450/510 . These bike have a Electronic box for sensor inputs. ( the engine temp sensor, a ambient temp sensor and something else..I forget). The point is, this Electronic box recieves these values and works some solenoid,( also forget what it is), and also work this cooling fan. If it's not too complicated, I'd like to mimic it's action to get correct fan function.

I have a wiring diagram of the models with the Electronic Control box but it doesn't show it's inner circuits. External wires to it include the sensors, the solenoid and battery power thru the key switch.

In general how are thermisters wired in indusry? In conjunction with what devises do they perform a function?

I wonder if I got my hands on a Husky Electronic box and just wired the 12vdc, the temp sensor and the fans leads I'd have it?

Dave

I was wrong. My sensor is in the head also. My Aprilia temp switch is in the radiator. Sorry for the confusion.

i used on/off kill switch combo from trailtech. mounted where my old kill switch was. very simple. i tried brazing a tempereature switch in at the radiator t but it kept coming on and staying on forever. switch is easy. fan attached right to my ofg gurards.

WARNING: LONG POST...

Ok, hopefully I've caught up now. So in the standard installation there's probably something in the electronic box which monitors the value of the sensor's resistance and is set to close the relay at a certain point and open it again at another point. Since you don't have that bit of electronics in circuit you're relying on the way the sensor's resistance changes to control the current through the relay's coil, and so to close and open it, which is not how it was originally designed to work. That would explain why you need the additional resistor, and why you can't get it to stop the fan at the right temperature even if it comes on correctly.

One thing you have to consider here is that you may be right to worry about overloading the sensor, and also the 50ohm resistor. If the sensor is designed to connect into an electronic control unit it probably won't be carrying much current in that configuration, only as much as the ECU needs to pass through it to read the resistance. In your present layout you're having to pass enough current to operate the relay, which could be much more than it's intended for. Hard to know what the total resistance is without doing some measurements of the sensor, but if it reached a very low resistance the overall value of your present circuit could approach 133ohm (50ohm resister plus 83ohm relay coil), so it could draw as much as 100mA. This would mean around 0.5W being dissipated in the 50ohm resistor as heat which may be more than it's designed for if it's a low wattage one, particularly as the surrounding air may be warm too so it will dissipate heat slower than expected (you could bolt it to something metal to help lose the heat but probably not a good idea if that's the engine!). So there's a chance the resistor will burn out at some point. The sensor could also be carrying more current than it's designed for - overheating may not be such an issue as it's obviously designed to get hot anyway, but it could still potentially damage the wiring depending on what current it's normally expected to carry.

So if possible the best idea would be to use the Husky electronic control unit as you suggested, because that way you shouldn't need the 50ohm resistor and you'd know you're not running too much current through the sensor. In theory I'd expect it to work with just the 12VDC, temp sensor and fan leads connected as you said, but it's impossible to be certain without knowing how it's wired internally (for example if it normally has an ambient temp sensor connected it may be looking at the difference in temp between that and the engine to decide when to switch on the fan). If there's any way you could borrow one of the ECUs or get it on "sale or return" so you could just wire it up temporarily and see whether it works, then you'd know whether it's worth buying.

Or you could just go back to using a switch on the handlebar!

In general industrial use, more often than not thermistors are wired through some sort of electronic unit rather than directly to a relay. It depends on the application but in many cases that unit is actually a computer of one sort or another which monitors several values and makes decisions based on the combination. For example I know one installation where a thermistor is monitoring the temperature of a motor and if it gets too hot the whole production line is automatically closed down to avoid damage. Another thermistor in the same production line monitors the temperature of a vat of liquid and applies more or less heat to keep it within a given temperature range, and photo sensors make sure a roll of material is lined up correctly. All of this is controlled by a computer which monitors all the inputs and either adjusts the settings, sends warning messages to staff, or shuts down altogether if necessary.

Phew, got to the end. Must rest fingers... :snore:

nasa science here... dimwits(me) beware... fitting a thermo fan has never been so involving !!! LOL...

True, but would you rather be reading another thread on, "What oil would you use"?

What I think I'll do,... I'll get a beffy resistor, clean up the installation, add a small simple key switch up front to run the loops 12vdc thru,... a master on/off so there's zero load on the battery when sitting.

Keep the little off/auto toggle switch I have just under the left side cover/# plate near the seat/tank juncture. It allows me to "cycle the power to the relay when the fans running needlessly.

A compromise, but I'd rather be shutting a fan off that's not needed rather than remembering to start one up because I'm overheating, ..... or think I am.

I know there's a thermal switch that can do this job right but for now I'll go this way.

The Husky thermister that screws into the head is about 1" long, and a 8mm x 1.0 thread pitch. IT's unlikely I'd find a switch of that configuration.

Dave

So now you're thinking about oil-cooling the resistor? Hmm, let me see now, that could work... anodized banjo unions... braided hose... new oil pump and reservoir... oil radiator with its own temperature-controlled fan...

Your switch suggestion sure sounds like a simpler method!