Overheating connected to AC?!

'99 VW New Beetle GLS, 2.0
I have the weirdest problem.

Blew a fuse...the first 30Amp on the battery box. It was killing my radiator fans and my temperature sensor was fried. The car didn't get a temperature signal at all, so it always threw the low coolant/high temp light right off the bat. Replaced the fuse, and the Temp sensor...problem slightly better. Now at least the car knew how fast it was actually overheating...meaning that light came on *slower* now...but it was still overheating on me. Did some hunting.
A housing on the right side of the engine was cracked, and leaking coolant and steam all over the place. Replaced that, coolant system works slightly better. There are no coolant leaks. Car still overheating, though.

Now, here's the REAL killer: The car is overheating because it is not properly using the radiator to cool the system. It's getting bad signals. My radiator fan works...one of them...but ONLY IF the AC is on at the time. If my AC is off, the fans never start in the first place. I thought it was because one of them was stuck, bad wire, etc....not the case. The wire is transmitting signals just fine when you pass a current through it...moreover, If you jump a signal straight to the radiator fan, bypassing the original signal source, the fan comes on....not stuck or damaged...just not coming on.
Okay..So I run the AC, sortof like a manual turn-on-my-fan switch.
Stop at a light. Car starts to heat up. NOW when the car starts to warm up to the "hey, we're getting hot now" temperature...the radiator fans turn *off*.

Yeah. Weird, eh? Here's the recap:

Conditions****What should happen******What does happen
Start Car, No AC --------------- No Fan ---------------------------No Fan
Warm Car, No AC----------------Trigger Small Fan --------- No Fan
Hot Car, No AC-------------------Trigger Large Fan --------- No Fan
Overheating, No AC-----------Trigger Both Fans --------- No Fan

Start Car, AC -------------------- Small Fan ----------------- Small Fan
Warm Car, AC -------------- Trigger Small Fan --------- Small Fan
Hot Car, AC--------------------Trigger Large Fan --------- Kill Fan
Overheating, AC------------Trigger Both Fans --------- Fan Still Dead


Now, I've been told there's a Fan/AC ECU module that can short, and cause this sort of issue. It is either a 14 or a 10 pin connector, depending on what was available the day they built the car...it's the Coolant fan control module. After some wiring diagram meditation, I've pinned down a few conclusions:

#1: This ECU is connected to the AC thermal cut-out switch.
#2: This ECU is connected to the fuse that *melted* itself in the battery box
#3: This ECU controlls which of the Fans comes on.


Now: Has anyone else encountered this problem, and if so, am I runnin off the wrong end of logic here? My theory is that replacing the 14 pin Coolant fan control module is going to ensure the proper electrical demons get excersized before my car blows up at every red light. (Problem complicated by my residence in the middle of the Arizona desert.)

Cause I really dont wanna have to run it off a bridge. :(

Don't drive it off that bridge!!!! - sounds like your waterpump is buggered which is normal for a Beetle of your age (unless it has already been replaced).
The impeller fails and results in no circulation. This has possibly caused your problems with the fans - I'd hotwire them BUT first I'd check that coolant is circulating because as I said before it sound like your waterpump is cactus.

fan control modules under the battery are a VERY common problem for fan fuses blowing. Also this module controls fan function when the ac is turned on. (theres a small 10A fuse for it on the fuse pannel in car)