PASSAT B6 BLOWER RESISTOR PACK.
This information only applies if you have basic climate control (Air conditioning) with a
switch that has four positions. 1, 2, 3 and 4 to control fan speed.
The Climatronic fan has a built in electronic controller, so NO resistor pack.
The circuit diagram for the blower circuit is shown below.
Blower switch position.
Position 4. Power is applied directly from the switch to the blower motor…Full speed
Positions 1 – 3 Power is applied to the blower motor via the resistor pack.
To prevent the resistor pack overheating, it is protected by a Thermal fuse.
Positions 1, 2 and 3 all supply blower motor power, through the thermal fuse.
If the thermal fuse “blows” the resistor pack stops working and blower switch positions 1, 2 and 3
So if your fan only blows in position 4, the thermal fuse on the resistor pack may have failed.
What to do next.
The obvious step is to buy a new resistor pack from VW. They are amazingly expensive.
You can attempt to mend your resistor pack.
Mending your resistor pack.
To remove the resistor pack.
Take off the cover under the glove box (above the passenger’s feet).
Look for a white plug with a bunch of wires going into it.
Slide sideways and pull down.
Disconnect wiring connector.
Below is a diagram explaining how the resistor pack works.
1. With the blower switch in position 1, power has to pass through all three resistors and the
thermal fuse to get to the motor so that’s the slowest speed.
2. With the blower switch in position 2, power has to pass through two resistors and the
thermal fuse to get to the motor so that’s the next slowest speed.
3. With the blower switch in position 3, power has to pass through one resistor and the
thermal fuse to get to the motor so that’s almost full speed.
4. With the blower switch in position 4, (not shown). Power goes straight to the motor.
You can see from this diagram that, if the thermal fuse “blows”, no power gets to the motor and fan speeds 1, 2 and 3 stop working.
If the first resistor fails, you lose speed 1.
If the second resistor fails, you lose speed 2.
If the third resistor fails you lose all three speeds just like when the thermal fuse blows.
First test the thermal fuse.
You can’t mistake the thermal fuse as it looks like a metal bodied resistor soldered between two of the terminals. Use a multimeter set to Ohms (continuity). Place one probe each side of the fuse
If the fuse is ok…it will read “0” Ohm.
If the fuse has blown it will read “1” (This means, open circuit, not 1 Ohm)
If the thermal fuse has blown.
It is easier to solder to the old thermal fuse wire than to the resistor pack pins.
So cut out the body of the thermal fuse with side cutters and leave plenty of it’s wire in place.
As a simple test, solder a piece of household fuse wire, (about the same thickness as the thermal fuse wire), across the terminals where you cut out the thermal fuse. Test continuity.
Try it in the car. All speeds should now be working.
Don’t leave it like this because the resistor could overheat and set fire to your passenger’s feet.
Buy a thermal fuse from an electronics shop and solder that on in place of your fuse wire.
It is hard to get a correct thermal fuse, so buy a selection. Use the lowest temperature one.
If that blows, replace it etc.
If the fault is not the thermal fuse, you will have to buy a new resistor pack.
It may be possible to repair a failed resistor pack, but if you knew how to do that, you wouldn’t be reading this.