Andy, he's going to do some on-vehicle testing before he sends it to us.

When I popped the head gasket in the hot rod my temps would hit 230 fairly quickly. After stopping and idling for 3 or 4 minutes the temp would be back down to the thermostat. Not bad for still pumping exhaust gasses into the coolant.

Success

Finally got the alternator installed, and got a break in the snow today, so I was able to let the fan run for an hour. It got cold and dark, so I didn't go any longer than that

It otherwise seemed to work just fine; no smoke from its controller, or turning off by itself.

I think at this point I just need to finish up the circuit board and start moving forward with building them.

X2

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Ok, I have some more questions.

Once the temperature reaches the set temp, the fan turns on. How many degrees do you want it to go down before turning the fan off? 5? 10? 15?

I have room for another dip switch to select between a big drop and lower drop in temperature.

Well, I guess I only had one question

I would say 10 degrees should be fine. And that is a pretty short run.

maybe 30 sec to 1 min if that at idle.

The reason I say that is based on what I do.

I have 195 degree thermostate.

So I let the fan come on at 205 to 210. if it takes it down 10 degrees it is right at the thermostate. It actually takes it down to 189ish before it closes I guess and the fan shuts off.

I don't think I would feel comfortable letting the engine get much higher than 210 to 220. Though I am sure I have hit 230ish at some point.

guess it would depend on if you had the turn on point still adjustible.
if you can't make the off adjustible, then I would do 10 degrees and if you want 20 for the switch. but I would be afraid it would never shut off at that point.
guess you could put up a poll.
see if there is a preference to the fan on temp and if they would want it to fight down from a higher temp.

The turn on temperature will be adjustable from 160 to 240. (I don't think I need to go any lower, or higher?).

Then once the fan turns on it'll run until the temp drops 10 degrees?

With the switch it can drop 5 or 10. 7 or 15. Or any other two temps that make sense.

I am guessing the dip switch is only a doubler.

I agree your range is fine.

I don't really see any use for it right now. I would just set it at 10 degrees and leave it.

save the switch for something else, like maybe a constant on. something that bypasses all logic and just shunts the fan on?

10 degrees should be plenty.

Did you get the alternator installed and the truck ready to test?

Everything look good?

I should be able to order the boards today or tomorrow. A week and a half to get them, a few more days for assemble and test, then they should be done

I can only think of 4 leads.
power, ground, sensor, power to fan.

What are your extras?
pins? standard like a floppy drive connector, or what is your plan.

also do you have a better idea on how to water proof it?

Starting on the left, there is
Power
ground
Trigger to fan
Status output
AC input
Sensor input
sensor ground

I couldn't find an ideal box, so I found one that will completely enclose the board. You (or me) can drill a hole in the box to run the wires through. Then you use the screw terminals to attach them to the board. I'm going to align the hole on mine to be pointing down (with be either side or the end of the box). The board will also be sprayed with a protective coating to help prevent any small splashes/condensation from doing anything bad.

The plastic black box is ~2"x4"x0.88" and has mounting tabs. The board is ~1.5" square.

The DIP switches are pretty tiny, and so is the knob to set the turn on temperature. Basically you'll set them with the top of the box off, run it up to temp to make sure it all works, then you can put the top on and forget about it. When I ship them out I'll have the temp set to ~210*.

do you have a picture of the box? or link.
might make a sugguestion.

go ahead and run wires out of the box for some of these folks.
or better yet a replacable plug of some sort. Lest too much trimming cause a problem. might be too much on the plug thing.

if it is a clam shell type I agree wires out the bottom and lift off cover should be "water proof" enough.

The box will look approximately like this one (it's a stock photo, so the dimensions may be off). link.

The screw terminal will look like this one link. Personally, I'd prefer to run the wires into the box and use the screw terminals, than have a bundle of butt-connectors just outside

I thought about adding a connector, but that would likely add another $10+ to the price The good ones are not cheap. And then I need to have the boxes cut to fit the plug, make sure it's sealed, etc.

not loving the box to be honest.
too many places it could leak.

is there more of a sealed on the top kind? clips on the side instead of screw holes that could leak?

not sure how to explain it, but if the top were screwed in from the bottom that would be a good choice.

how are you mounting the board to it?

A similar style looks like this. link, but to change anything, you'd have to unmount the entire box, then take the top off.

I'm not seeing any plastic boxes, with a mounting flange, that are sealed with a gasket. I have some similar plastic boxes from other projects that close tight enough that unless it's submerged in water, they pretty much don't leak at all. A casual splash would be fine. It also wouldn't be too hard to run a thin strip of RTV around the edge before putting the lid on.

There are plenty of aluminum boxes with seals and flanges, but the cost goes from ~$4, to ~$12-15+ each. And if the customer drills the wire hole, metal flakes going everywhere could be a concern.

The board will sit on four 1/4" tall plastic standoffs that have a sticky base.