Thanks alfons, looked it up and i see they can make custom ones, the variety i would prefer isnt one of their premade parts. But for someone with a 195 tstat, they have an option there. They only have normally closed in the dual temp one I would like. If I didn't use the volvo relay though, and had access to the n/c contact on a set of relays, it would work.

So I ran the 2 speed cougar fan at the races lastnight, it was perfect, stayed well below half the whoe night. Not once did i think it would heatsoak. In fact, the only time it made it within a 1/16th of half was when I did a speed run on the way home.

 

Hey FrenicX, you wouldn't happen to remember or know the diameter of the stock fan would ya? Then again I only have the 3.7 but was thinking of putting in a flex light + spacer some time. Old school trick better than what's in there?

 

FrenicX, if you have a basic understanding of electronics, you could do away with the thermal switches all together and use the output of your OEM thermal sensor. What you'd need to do this would be a small handful of components like a dual comparator chip, a couple of NPN Mosfets (a type of transistor), some resisters & diodes and put this together in a small box. This component mixture would then take the thermal sensor output as an input voltage to be used for comparison on switching points. It would compare this voltage to the 2 reference voltages that you would have set up to represent the low and high speed switch points and once each of these points are reached, the mosfet related to that output would switch on a relay (the whole thing could be done without relays, but this approach in dealing with low amperage levels makes this box a lot easier to construct). From these relays outward, you'd have no difference to your controller system. This comparator & switch box could be designed with a couple of variable resisters so that you could set the desired temperature for each switch point. The whole thing is fairly easy to design or even to look up on the internet and copy a schematic or two, what you would need to do in order to select the correct resister values is to do some research on the OEM thermal sensor - you need to know what the resistance (or voltage) vs temperature profile is for that sensor.

 

Hey, great work FrenicX. Your research & build will save a lot of others a whole bunch of heartburn in how to use these really good & cheap cooling fans - they just need to keep in mind to get the 2 speed vs the single speed when doing this.

I remember reading somewhere that that thermal switch company has a bunch of switches that aren't in their catalog but are on their inventory list. They might have exactly the switch needed and it wouldn't be costed as a custom make.

 

Saw on the U-Pull website here that they had just dumped a V70 and a 3-series in the yard so I went out and pulled the 2-speed relay ($2.99) and two temperature sending units ($1.99 each). I have to go back because the sending units were not the correct ones. I think they are just temp for the gauges and maybe a single-speed fan sending unit.

I couldn't find an old taurus or cougar either, so I'll likely have to find one at another yard (or cruise the university bars).

Maybe this fall it will get installed!

 

You can test the temperature units to see if they're switches or sending units. If it's a switch, it should have no continuity at room temp (I believe they're normally off), so that should be an easy check. If you want to check the switch point, put the end into some water, add a thermometer, heat up the water until the unit shows continuity (turns ON) and then you know for sure and you also have the switch point temperature. For a sending unit, you can go through roughly the same process with the water, but you should make yourself a graph to show resistance vs. temperature, especially around the temperatures you want to do things with (with relays, you won't be able to take advantage of a sending unit).

 

BMWs will probably be hard to find out there, but if you find a 3 series from the 90s, it should have the 2 way switch. It will have pins/wires. Audi/vw has one too, but its huge and hard to find a place for.

 

There are a few different thermal switch setups that you can find on-line with a bit of searching. FrenicX's whole writeup can be used with different thermal switches, for example, here's a link to one that you can get to fit into the heater hose. You can use the same concept with single temperature switches and just add more of them to the heater hose using a brass barbed T similar to what's shown in the link. Fittings can be found on-line or locally at any fluid fitting supply outfit, you just need the size of the hose and the thread type & size for the switch.

 

GOT IT! Went to their other yard across the river and found it on a 318i. My problem was that I was looking in the wrong place! The one I found was mounted on the side of the rad. The first car had the rad removed, so it was likely gone with that rad.

My switch has the temps stamped on the side of it 91C and 99C.

While there, I found an '04 Dak with the new multifunction switch on it, I pulled that without much effort (well, I had an electric impact gun making removal of the steering wheel easy). I don't need it yet, but these things are hard to find.

 

So I have been looking for the part that would make things easiest for threading the 3/8npt to m14 adaptor. The bushing idea turned out not to work so well, as the vise ends up squishing it because it gets so thin, and its brass. Then it binds on the drill bit.

So I found a 1.5 inch fitting that was 3/8npt on both sides, I threaded it into a ballvalve and vised that instead so the fitting didn't squish. The ID of this fitting was already 1/2 inch, which is the right size for a m14x1.5 tap. Then I cut it in half and had two usable ones, but damaged one while removing it from the ball valve. Worked very well.

I don't need the test piece since I don't have a spare npt plug in my timing cover, so its up for grabs.