96 almost bone stock 2.3L. Fan is from a 3.0L Taurus. I have used several high current relays on other installs, including an 85 amp diesel glow plug relay (f%#*ing $50), and these are the best I've found, very SOLID construction.




On the low speed the fan looks and cools good, but I'm having control issues.

I'll start off by trying to determine if my HVAC control head is working right. I've read numerous places that you are to tap into the purple wire to feed the 12V side of whatever relay you are going to use to fire up your fan (cannot find the HVAC control diagram anywhere). I decided to tap into the compressor itself, since it was close enough to the relay:



I checked it with my voltmeter, it went 12V when both the AC settings were on, thought I'd be ok using it.

It trips the relay fine, problem is, that wire also goes hot when the fan switch is also in the non-AC upper vents, high-low, and window defrost?!?

I pulled the HVAC control out of the dash, found that purple wire and it mirrored the compressor voltage at the different knob positions:

(The purple wire is the one stabbed on these)
High-low:

Low-Defrost:

Defrost:


I know there is a couple of Ranger guys on here, is this like anyone else's unit? I have a sneeaky feeling the purple wire is only supposed to go hot when the AC is on.

Second problem is the thermostat I got to run the fan relay, it's from summit, Summit Electric Fan Thermostat Sending Units, 185 on, 170 off. Here it is installed:


I got this one because I've had zero luck with the cheapo adjustable ones from autoparts stores (the ones with the probe you stick in the radiator fins) they fail and in my case bled off voltage from my battery. Not what I wanted with my daily driver. Anyway, here is what this one did when it came up to temperature:

VIDEO

The thermostat rapid fires as it grounds, (the test light is between the thermostat and the positive battery) you can't see it very well, but the fan shakes the whole radiator and the relay can't be too happy like that. I guess it's just not gettting enough hot coolant fast enough.

Also that location doesn't seem to vary temperature very well with the rest of the cooling system, the heater is almost never on here in southern Florida so I guess coolant is never really cycled by it.

When the thermostat is seeing temps like this:

The rest of the coolant is this probably within 20 degrees of this temp:


The fan won't kick off either even at highway speeds, cruising along last night at 60mph for 20 minutes on 19 the thermostat was still on. I want to move it to the upper radiator hose but I'll need a large diameter pipe with a bung on it. I can weld one, but don't really like the thought of all that mild steel in my cooling system and a custom aluminum one is pretty pricey for something like this. If anyone has an idea of a pipe with a 3/8" NPT tap on it I'm all ears.

I have done a couple of taurus fan installs. Both installs went very well, with the exception of the adjustable thermostat repeatedly failing and bleeding off voltage.

I'm not a really a newbie at wiring, but I can't find a wiring diagram for the HVAC controls so I thought I'd see what you guys thought.