According to your drawing your switch is a 207/194. My understanding of how the switches worked is that the circuit closes (fan comes on) at the higher temperature (207) and stays on until it reaches the lower temperature (194). Then the engine warms up to 207 and the process starts over.

If it came on at the lower temp (194), the fan would come on, temps would drop to 193 and the fan would shut off. Then 3 seconds later the temp would hit 194 again and the fan would come on. Yo-Yo fan.

Does the 1.7 show voltage? IIRC the 2.1 does.

Yeah, I saw that on the diagram and always thought those on and off numbers were the OEM switch. I didn't draw up the diagram, I copied it from a thread on the other forum years ago. It's highly likely that my memory stinks...or that my ADD has played it's tricks on me and that info you just picked out is perfectly accurate and I've been chasing a ghost in terms of the on switch.

The good news is the car is home, I had no issues with it. I'm going to test a few things tomorrow morning. See if my alternator might be failing and simply not up to the task of that hog of a Taurus fan.

Actually the 2 numbers in the switch spec is just a way for the manufacturer to cover his ass and define a repeatable tolerance. In this case, the mfg. guarantees that the switch will close/turn on whenever the temp is greater than anything in the range of 194 to 207*F. IOW, they guarantee it will be open/off at temps < 194, and closed/on at temps > 207. Another way of doing this is to specify a single temp switch point (e.g., closes @ T > 197), and include a tolerance factor, (e.g., +/- 10%).

Logging voltages is a good suggestion... Unfortunately the Rtek 1.7 lacks the serial port to allow tuning/logging with a palm device that the 2.x has.

That's what I'm thinking, if the alternator can't sustain a steady voltage of at least 13V while running all electrical loads and charging the battery, things will get wonky. Which is why I agree monitoring voltages on the next drive is a good idea. That Taurus fan has a colossal current draw, and can quickly discharge a battery. When you were running the fan on the manual switch for a prolonged time, I think the battery discharged deep enough so that the alternator couldn't support all the electrical loads AND charge the battery, so as soon as system volts dropped below 12 or so, fuel delivery and/or ECU control started failing.

Thermoswitches are notoriously unreliable.
The aftermarket stuff is pure junk.
A lot of the aftermarket electric fans that use those electric controllers with the push-in temperature probe (into the radiator fins) fail consistently.
The stock units are a lot better, but I still won't trust it.
I was running off the stock FC thermoswitch for years, but even that failed after a few years of use.
I was running the Spal PWM controller until I accidently short circuited the thing.
Now I run my fan off the Haltech E8.


-Ted

Here is what I have found. My alternator seems to be acting the way a modded alternator should. It needs RPMs to keep 14v. Even with the fan not on, at 300-500ish RPMs it's not cracking 12.something volts. Without the fan running I bump the RPM up to 1k and my voltage climbs to around 14v. If I have the fan on and RPM at idle (300-500) I can watch my battery voltage drop. In a couple of minutes it went from 12v down to 11.8ish. With the fan on I need RPMs at 1-1.5k in order to see 14v on my DMM.

What is curious is that it did not behave this way before I needed to repair the wiring, but I guess that's just how things go.

I'll need to start planning for something different with my fan and charging system. With a TMIC I'm very limited on alternators. Before adding the efan I had an FD alt and that barely fit under my TMIC. With it squeezed under there the TMIC was making too much contact with the hood. I'd love to do a Taurus alt, but I'm quite sure that's not going to fit. I may have to start planning for a FMIC.

I forgot you had a modified alternator... So at high idle >1K or so, you're seeing at least 13.5 V and the battery charges even with all the electrical loads on? If that's the case, you need to raise the RPMs of the alternator at idle -- an overdrive alternator pulley would do this. Don't know where you can get one of those though. Underdrive pulleys can be had, but I don't know anyone that makes an overdrive pulley for an FC alternator.

An FMIC seems like a drastic solution. Hmmm, I've got a zit. I NEED A FACELIFT!!! :tongue1:

We are running a stock JDM alt with the GM e-fan Cake recommended in his e-fan how-to controlled with a push-thru thermoswitch pulling air thru a Godspeed rad. It was 104 in the shade last week and I drove the car in traffic to the office with the a/c on and the Pioneer 7" LCD head unit on and had no issues with heat or voltage.

I would start by seeing if I could get my hands on a stock alt or at a minimum having yours tested. If something changed after your short, that would be the logical place to look.

Alternatively, Id swap to the GM fan. Maybe it doesnt have the watt-consuming machismo impact of the Ford fan, but yall don't spend much time above 104 there so it'll probably keep temps managed.

Yep, no way any underdrive pulley is going to work on a daily driver FC.

Even with my FD alternator on my FC, I run a stock size pulley - both on the main and alternator sides.
It barely charges at night, at idle, with the headlights on...
(I have no A/C.)


-Ted

I'm going to have mine tested. After testing the alternator with fan on and off the car sat till today. I go out today after work to drive it some to find a battery too low to engage the starter. Now I did have the car idling and the fan running some, but I wouldn't think that is enough to drain the battery this low. I'm waiting till after dinner and I'll go out and see what kind of voltage the battery has.

The last time my engine did this little burp with the engine wanting to stall out I came out a couple days later and the battery was dead. I charged it and checked for parasitic drain and found none. My DMM showed between 30-40mV. Which makes it sound more like I have an alternator problem.


I'm going to look into an overdrive pulley, but to be honest I don't even know where to start looking. I'll start by googling alternator pulleys and see what I can turn up.

Update that is about as bad as it can get....

Was still in break in mileage on the engine and I have apparently lost all compression on the front rotor. I was driving as you should during break in and at 30 mph and maybe 3500 rpm the engine went to crap. All the sudden was barely idling, running so rough that the entire car was shaking.

I wasn't driving the car much at all while I figured out electrical problems and why my engine was idling very rich (10.7 afr at idle). When I pulled the leading plug for compression test the front one (same one with zero compression) was covered in gas and sandy grit. I thought I had found the cause of my poor running engine and probably my low afr...that my front leading coil wasn't igniting or was igniting weakly.

Did the compression test and the needle doesn't even budge. I pulled the tester to feel the puff of air while cranking and they are virtually non-existent. My hopes are that it's stuck seals and springs from running rich...but I realize that's a long shot.

This may spell the end of my rotary days. At the very least it will be some time before I re-rebuild it. I'm trying to finish up a 2nd degree and absolutely do not have money to spare right now.

I don't expect to get compression back on the rotor, but I'll try seafoam steaming. If I can't get it back to good compression I will at least teardown the engine and see what and why. If I find internal damage then I"m most likely done. It's getting harder and harder to find quality parts.

Sad day, sad day indeed!!