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When doing a TT conversion, the 2-speed TT A/C fan is often skipped as unnecessary. While it may not be mandatory for a "successful" swap, it's not difficult and helps to complete your swap. I had a TT parts car at my disposal, and I wanted my TT swap to be as accurate and complete as possible, so I took the time to dissect the factory configuration and transfer it to my NA. As you'll see, the swap is pretty simple. Required Parts
- TT Fan
- TT fan connector w/ wire leads
- Fan relay w/ connector and wire leads
Additionally you'll need a soldering iron, heat shrink, head gun, wire strippers, wire loom, and some wire.ECU Wiring
NA and TT both use Pin #19 for the fan's High Speed. The TT uses Pin #6 for a second Low Speed. As denoted in the FSM, the NA EFI harness does not contain the white wire which connects to Pin #6. Again, if you're using a new TT EFI harness for your swap you don't have to do anything yet because the wire is already present. Those reusing their NA EFI harness will need to add this wire to their EFI harness. Both Pin #6 and #19 are ground pins for relays. As you'll see below, the High speed and Low speed relays are supplied with 12v power, and they are triggered when the ECU grounds either Pin #6 or #19. 
These plug into the Engine Room Harness connectors next to the relay box on the fender:
 Fan Connectors
The fan connector lies at the other end of the circuit. Examining the NA and TT fan connectors, the NA has two wires and the TT has three. However, two of the TT's wires are the same wires for the NA connector. All we need to do is connect the existing black and green wires to the corresponding wires on the TT connector (by cutting off the NA connector and splicing wires), and provide the missing third (blue) wire. NA Fan Connector:
 TT Fan Connector:
 Fan Relays
The missing blue (low speed) wire and the existing green (high speed) wire both come from the relay box on the fender. The two fan relays are located in the relay box:
One look at the NA relay box and you quickly notice it's missing a relay. That missing relay is the Low Speed relay for the TT 2-speed fan.
Relay Installation
- Remove the relay box from the fender and flip it over.
- Remove the back panel to expose the wiring and access the cavity for the new Low Speed relay.
- Insert the relay connector until it clicks into place.
- Locate the thick Purple wire for the existing High Speed relay. Replicate the factory wiring arrangement by splicing the thick Purple wire for the Low Speed relay into the thick Purple wire for the existing High Speed relay. Here's a picture of the factory splice:
 - Likewise join the thin Green wire for the new relay with the thin Green wire of the existing relay (again this relicates the factory wiring arrangement).
- The thick Blue wire from the relay goes to the connector for the 2-speed fan. Integrating this into the existing harness is possible, but would be VERY difficult. Instead I routed the wire separately and as cleanly as I could in its own plastic loom. In the picture below you can barely see it behind the large factory bundle at the bottom.
- The thin white wire goes to the grey connector on the engine room harness (next to the relay box). Take your time and you can unwrap and rewrap the existing connector wires for a clean factory look. Ideally this is just a matter of inserting the pin in the connector, but if you don't have access to a complete relay connector wiring assembly you'll need to come up with a pin for the connector.
- Reinstall the back cover, reinstall the relay box, and install the new relay. It should look like this:
Wiring Assembly
For clarity, here's a picture of the two fan relays and all associated wiring and connectors:
 That's it. The NA and TT fans are physically interchangable with the exception of the connector.
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NA to TT, starting from the ground up... Proper check valve inspection per the FSM...
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How To: TT 2-Speed Electric Fan Swap (for TT conversions) - 
