E-fan conversion /designing an e-fan controller

Splitting this from another thread:

ratdude747 said:

I've also been hesitant on the e-fan swap, mainly because getting one to work well (and not be a hacked up mess) seems to be more trouble than it's worth. I have a degree in Electrical Engineering technology so I could design a fan controller; (warning: electrical design jargon ahead) a temp sensor (the one for the temp needle would do) fed to a positive-feedback amplifier (or a schmitt trigger buffer) which would (via a transistor or the like) drive a fan relay. However, I'd also want it to switch the fan to high speed when the AC was on, which hopefully could be obtained from one or both of the pressure switches (not sure about the AC wiring, all I know is what each switch does in relation to AC pressure). IIRC such a fan doesn't yield much of a fuel mileage gain, which is what I'd be mainly looking for.

Edit- I looked,saw this:

http://www.fordrangerforum.com/561523-post6.html



That dark green/orange is a viable easy-to-integrate signal. edit 2: Although that's only the compressor. There has to be a way of getting the compressor to start... which would originate at the AC switch in the dash... looks like I need to look for a more complete diagram and/or start probing my AC wiring.

Crap, now I want to design a controller. Darn it!

Click to expand...

... which brings me here.

For the 1995 3.0, here's what I'd like to know:

-An acceptable operating temperature range (so I know when to turn the fan off/on)
-*A temperature vs resistance chart/constant for temp gauge sensor (if I go the analog route for designing the controller)
-*A temperature vs voltage chart/constant for the PCM's temperature gauge (if I go the digital route for designing the controller)
-*An accessible wire/signal that is on whenever the A/C is on (not just the compressor, this is to force the fan on/full speed)
-A good fan to buy/junk yard that will fit w/o changing my radiator

*- I could find this out empirically; I do have a BT OBDII dongle and Full Torque.

I know they make off-the-shelf controllers but AFAIK they require adding sensors and don't have an A/C bypass function.

I'm an electrical engineer by trade/education (BS EET Purdue, class of 2015) and I know how to design circuitry like this. As mentioned above, I originally though of doing it old school with OP-AMPs and the like (it's a classic circuit I had to design for one of my exams a few years back); however, as cheap as microcontrollers have gotten, I could very easily design this to run off a cheap arduino nano knockoff, as I've done in the past. I did this to make a prank alarm module that was triggered off the dome light, pulsed the horn, and used an LED and switch in the dash for status/activation.

In fact, I'd even be willing to design a circuit board for this and Open-Source the design so anybody who wanted it could make it.

I already have a six-position fuse box that I added under the hood (uses mini-ATC fuses) with 4 positions open; so that gives me up to 30A fused for the fan.

Yeah, I'm as nutty as they get, and I'll probably not bother as my clutch fan works fine (albeit with some troubling cracks in the fan plastic). I do a lot of long-distance driving in my truck, so a few highway MPG would be nice (to make up what I lost from my camper shell).

Thoughts? Comments? Wiring diagrams?

I suggest using what factory systems use, and KISS to avoid problems.

There's plenty of off the shelf aftermarket controls. I'd use the bottom rad hose outlet to control fan on/off. You can buy a hose adapter which will accept a temp switch. The switch should be NC for fan off as a fail safe and NO for fan on.

If you try to use the ECT, which is on top of the engine, then if your coolant is low it won't register a temp to turn fan on. I replaced my gauge sender with a digital gauge by using an adapter, or you can by a scan gauge which will read off the ECT.

Scan Gauge here.
Temp Gauge here.

You can buy controllers that progressively spin the fan. I'd use a separate switch for A/C.

Consider two fans instead of one big one, even a small pusher for the A/C.

More good ideas will come from other forum members.

Rearanger said:

I suggest using what factory systems use, and KISS to avoid problems.

There's plenty of off the shelf aftermarket controls. I'd use the bottom rad hose outlet to control fan on/off. You can buy a hose adapter which will accept a temp switch. The switch should be NC for fan off as a fail safe and NO for fan on.

If you try to use the ECT, which is on top of the engine, then if your coolant is low it won't register a temp to turn fan on. I replaced my gauge sender with a digital gauge by using an adapter, or you can by a scan gauge which will read off the ECT.

Scan Gauge here.
Temp Gauge here.

You can buy controllers that progressively spin the fan. I'd use a separate switch for A/C.

Consider two fans instead of one big one, even a small pusher for the A/C.

More good ideas will come from other forum members.

Click to expand...

Well, I did find wiring diagrams:

http://www.diakom.ru/CAR/Ford/1997/Ranger/SYSTEM WIRING DIAGRAMS/

(They're for 1997, but for the most part they're the same)

Purple wire going to one of the A/C switches is what I want. 12V when AC is on, open when it isn't.

If they make a fan controller than would integrate well with what I have (and would have such an AC override), then I'd just do that. However, all I saw required adding a third temp sensor and all sorts of BS Id rather avoid.

While for most it's too much trouble to design their own electronics, I have a degree in such and for me it's a fun challenge. Some electronic design, some embedded C programming, and some PCB design.

ratdude747 said:

While for most it's too much trouble to design their own electronics, I have a degree in such and for me it's a fun challenge.

Click to expand...

Works well and simple with relays. As well auto relays are robust.

Maybe you could post your circuit and let us know how it turns out.

Rearanger said:

Works well and simple with relays. As well auto relays are robust.

Maybe you could post your circuit and let us know how it turns out.

Click to expand...

That was the plan. Relays for the actual fan driving.