Upgrade Fan: Install 450W Fan

Hello,
I want to install a 450W fan, but I'm having a problem.

specifically, the fan control, particularly the after-run control.
According to the wiring diagram (standard 2.0E, this is how it's done), it's not entirely clear. Since I have a 1.9TD model manufactured in December 1991, and in my car, the relay for the afterglow function is located in slot 3, not in the additional bracket 13.
"Only two cables (red and brown) go to the connector behind the left headlight. However, three cables (red, red/white, and brown) continue from there, although the red/white cable is not connected!"
The rest is clear - Thermostat switch, fan ST1 and ST2.

How can I now connect the main control unit (1H0 919 506) for the 3-speed, 450W fan?
For example, the brown/white cable is for the thermostat switch and the fan overrun function, and the red cable is for...
Please specify which connector and cable color are located at the central unit.

Waiting for your help.

Hello,

I'm missing a lot of information here, which makes it difficult for me to help.

- What type of vehicle is it?
- What vehicle/engine is the 450W fan from?
- How many speed settings do the two fans have?
Do you have the wiring diagrams for both fan control systems, and could you send them if needed?
- and: WHY do you even want to modify it? (More levels? More cooling power?)

You seem to have described your problem very clearly, but the general information is completely missing.

Regards,
Private.

Okay, so to your questions:

Passat Variant, 1.9L TD, manufactured in December 1991, with an AAZ engine.

A fan, 2 speeds, 250W, from my car. Another fan, 3 speeds, 450W, from a VR6 engine.

I have both circuit diagrams. I can email them to you, but one of them is the standard diagram from "So wird's gemacht" 2.0E.
The other one is a VR6.

I want to retrofit a Diavia climate control system, and it shuts off at a coolant temperature of 105°C. To prevent this, I was advised to install a more powerful fan.

The wiring harness for the air conditioning and the 450W fan is already in place, and I just need to figure out the control logic for the fan's run-up sequence and the power supply for the first and second stages.
The third stage is directly powered by the battery and controlled by the main control unit. The first and second stages are also controlled via the new control system.

Can I simply remove my existing relay and connect the brown/white wire from the new sensor to socket 3 on the ZE control unit, where the wire for the "follow-up" function (5/T) is currently connected?
I would be grateful for any help!

Hello.
"Why do you want an after-fan function? The AAZ engine doesn't have an after-fan function, only the gasoline engine does. If you need wiring diagrams, feel free to ask. I have all the original wiring diagrams from the 35i model up to the facelift. If you're retrofitting air conditioning, also consider the large radiator that extends across the entire width. Also, the coolant connection on the cylinder head may need to be replaced. With air conditioning, there are two sensors: one for the coolant temperature, which you already have, and an additional double switch for the air conditioning, one switch for the 3rd fan speed, and one for air conditioning shut-off. You can leave the brown-white wire from the fan control unit disconnected."

Best regards, Benno.

Which cables on the control unit do I need to switch to activate the third stage?
1. and 2 are controlled by thermal switches.
Since I had already installed the necessary components, I wanted to manually shift into the third gear.

Sure, here's the translation:

"Hello"
Jörg.