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Discussion Starter #1
Vehicle is a w8 4.0. I have a lot of silly faults that are not going away by component replacement. I have the wiring diagrams for the pinouts for the various components so have had no trouble making sure there are no physical problems.

But I would like to know whats going on in my ECM. I have seen a few various schematics and logic diagrams for different ECMs. In fact I saw a program that you could input the different operations to find out what the responses for the ECM would be and how it controls the different components. I think there was one associated with a diagnostic device.

Unfortunately I have been unable to find one for the VW or more specifically the w8. Where would I find one of these?
 

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Hey so no winner on this yer? I have been through a bunch of faultfinding and can only trace my problems back to my ECM which to me is just a computer with lots of functions so far.

If I start my vehicle from cold, the fans will start up, and run for about 10min after shutting off the engine. Even if I run it for less than a minute, ie, cold.

I have a new thermostat in the vehicle. I have measured the resistance through both temp senders from the ECM pinout to find they are the same, and are only 0.1 ohms higher than a new one on the bench - so their input into the ECM is sweet.

I really need to find out the logic that controls the fans on my car - like, what is it that decides to run them and at what speed?
 

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Looking at Bentley schematic 72/15, I see the W8 "Unicorn" has G83 "Engine Coolant Temperature Sensor (on radiator)," green/white and white wires.
I'd bet that's what controls the radiator fans. It's surely in some measuring block in VCDS...
 

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That tied into the upper fender harness on both the V6 (relay/controller under the frame horn) and the 1.8T (relay in the back upper relay harness under the dash. None had wires directly to the ECU, but I could check the harness plug at the driver's side footrest to see which color plug is was there.
 

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That tied into the upper fender harness on both the V6... and the 1.8T. None had wires directly to the ECU....
The W8 is a unicorn... on the W8, this is a 2-pin analog sensor, i.e. a thermistor, not a double temperature switch like the other engines. The W8 has variable speed fans with integral controllers, where the other engines had a 2-speed fan with the relays and resistor (for low speed) in the places PZ noted.

Just thinking... my 2005 A4 (B6) has two variable speed electric fans. I'll bet it uses a similar sensor... Yup! ECS Tuning lists 06A 919 501 A for both my A4 and the W8. On the A4, it's right down at the radiator outlet, where the temperature switch was on my 1.8T Passat.
 
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