OEM Fan Control Question

[J-Groove]

Long story short, the Flex-A-Lite fan controller has bit me in the but again, I am tired of that system. So, before I mess with it again I'm wondering...


I know the '94+ ECU controls the fans with the temp sensors one way.

And I know the '91-'92 fans are controlled through themselves.

What I don't know is what a '93 ECU does.

I currently have a '95 N/A wiring harness controlled by a '93 TT ECU. Could I just plug in a 2nd gen radiator fan into the harness and call it a day?

I originally went with a fan controller because I used to have a '92 TT ECU in the car and it was the easiest option. ut now that she is a '93 I'm hoping I can eliminate it.

Thanks,
-John

[stealthee]

93 uses the same fan sensors as 91-92. 94 was the first year they went to sensors in the water housing.

As far as how its controlled, I am not sure. I always thought it was controlled the same, just had different sensors in different locations.

[cjbyron]

94+ uses ECU output at pins 20 and 21 for Radiator Fan high and Radiator Fan low (respectively). The ECU uses a ground driver at those pins to turn on the fan relays. 91-93 those outputs are A/C clutch clip input and Fuel Pump Relay. IIRC the wiring harness from the ECU is separate from the engine bay harness that has the fans wiring.

[stealthee]

Now that you say that, it sounds right. I think I remember the 1g parts cars having the rad sensor wiring in the body harness.

[Tackhammer]

Im too lazy to research what happens when you have this harness with that ecu with such and such fan and radiator X

Thats why i just made my life simple and used a tt harness with a matching gen ecu and radiator, but aparently routing a harness through the firewall is more difficult than re-inventing the wheel

[RealMcCoy]

In short, you have a a harness that requires ECU control of the relays, and an ECU incapable of such... One or the other has to change to use factory controls.

[Tackhammer]

J, Heres what i did to Coop's (taken from the forum where all the a-holes that dont know anything hang out)

DCIV wanted his condenser fan to be on all the time and his front mounted flex a lites to be switched via a temperature switch. Since he already had a low temp thermostat i suggested he get a low temp switch commonly sold for fords and GM's.

First I tapped one of the holes in the radiator to fit the GM switch and wired the switch to the HI relay via the oem harness. I also had to ground the radiator since this switch uses its body as a ground and the radiator is isolated from the car chassis. The ground also got wired to the oem harness connector where the oem switch was connected. The low temp switch now takes the place of the oem HI relay switch. (the low is just used to plug the hole)




Next i wired the Flex a Lite fans to the oem wires that once powered the oem fan. The polarity was reversed on these because the fans are front mounted pushers instead of the oem puller............




I then wired the condensor fan to the wires that once went to the resistor and made a couple modifications to them............




And here you can see the whole setup can be removed from the car by simply unplugging 1 oem connector......Or you can remove just the condenser fan by unplugging 1 oem connector........




Also, i went ahead and drew up a new schematic diagram so if someone works on this 5 years from now, they are not scratching thier head. If i had one of these for every wiring abortion i have come across, i would be a happy man with a few less gray hairs.




At Top Gear Engineering, we dont fuck around............

You can do the same thing using a 1st gen radiator and a stock switch, in which case you would ground one wire from the switch instead of grounding the radiator

Your wiring will be a little different depending on the year. etc of the different parts of your system, just let me know if you have any questions, or want to fly me out there to do it for you

[Tackhammer]

You can do the same thing using a 1st gen radiator and a stock switch, in which case you would ground one wire from the switch instead of grounding the radiator

Or your alum radiator, all of them ive seen have the threads for the 1g switches