Heater fan will not run all fuses & relays ok. discounted power plug reconnected works ok left over night will not run,

Fan relay may be bad or the speed resistor opened.

Check connectors and wiring, probably vibrations are interrupring some bad connector.

There is a 50amp heater fuse, then a heater relay. Once power gets to the blower motor, the resistor and fan switch provides the ground circuit.

Smack it and see if it comes on. If it does then the motor brushes are bad. If it does not come on, check the fuses. If the fuses are ok, check the voltage on the plug to the motor.

if the fan still works on highest setting only the fan speed resistor block is faulty.
if the fan doesnt work on highest setting check for power at fan while on highest setting with globe test light, as well as checking fuse for fan. 2 wires one power other is earth. if power is there the fan motor needs replacing so long as the earth wire is also ok check with voltmeter on Ohms for continuity should be a couple of Ohms any higher is no good.

It's marked AC and it's in the under hood fuse relay center, near the battery. The ballast resistor can fail too it's the device that if you follow the wire from the blower motor, it's in the heater box next to the blower and it can be unpligged , melted and just bad. Connect a test light between the two wires that connect to the motor, and with the key on, work the heater controls, to see if the light will come on in any position, wiggle the connections watching the light. If it's not working you might still have power so connect the test light between the body ground and the wires to the motor and you can find that you have power but not ground. The blower relay in in the firewall fuse relay center, standing in front of the car behind the engine it's the third relay from the left, under the Maxi fuse panel. This panel has two black covers and it's under the left one. The resistor is right under this fuse panel and it can have two plugs connected to it. The two wire connector is just power and ground. and it's on all the time the power from the maxi fuse. The maxi just makes the high speed though the relay and the lower speeds are controlled by the number 50 fuse in the insrument panel fuse panel number 50 it's a 25 amp fuse (clear)

Check the fan motor runs ok if power directly applied to it,
if OK:-
check operation/replace blower motor control relay (if fitted),
check fan speed control resistor pack- usually mounted in heater air ducting.

Hi,

Here is the fuse relay diagram:

MKIV FUSE LIST
1. Washer nozzle heaters, glove compartment light, memory seat control module (10A).
2. Turn signal lights (10A).
3. Fog light relay, instrument panel light dimmer switch (5A).
4. License plate light (5A).
5. Comfort system, cruise control, Climatronic, A/C, heated seat control modules, automatic day/night interior mirror, control module for multi-function steering wheel, control unit in steering wheel (7.5A).
6. Central locking system (5A).
7. Back-up lights, speedometer vehicle speed sensor (VSS) (10A).
8. Open
9. Anti-lock brake system (ABS) (5A).
10. Engine control module (ECM): gasoline engine (10A); diesel engine, Model Year 2000 > (5A).
11. Instrument cluster, shift lock solenoid (5A).
12. Data Link Connector (DLC) power supply (7.5A).
13. Brake tail lights (10A).
14. Interior lights, central locking system (10A).
15. Instrument cluster, transmission control module (TCM) (5A).
16. A/C clutch, after-run coolant pump (10A).
17. Open.
18. Headlight high beam, right (10A).
19. Headlight high beam, left (10A).
20. Headlight low beam, right (15A).
21. Headlight low beam, left (15A).
22. Parking lights right, side marker right (5A).
23. Parking lights left, side marker left (5A).
24. Windshield and rear window washer pump, windshield wiper motor (20A).
25. Fresh air blower, Climatronic, A/C (25A).
26. Rear window defogger (25A).
27. Motor for rear windshield wiper (15A).
28. Fuel pump (FP) (15A).
29. Engine control module (ECM) gasoline engine (15A); diesel engine (10A).
30. Power sunroof control module (20A).
31. Transmission control module (TCM) (20A).
32. Injectors: gasoline engine (10A); diesel engine (15A).
33. Headlight washer system (20A).
34. Engine control elements (10A).
35. 12 V power outlet (in luggage compartment) (30A).
36. Fog lights (15A).
37. Terminal (86S) on radio, Instrument cluster (10A).
38. Central locking system (with power windows), luggage compartment light, remote/fuel tank door, motor to unlock rear lid (15A).
39. Emergency flashers (15A).
40. Dual tone horn (20A).
41. Cigarette lighter (15A).
42. Radio (25A).
43. Engine control elements (10A).
44. Heated seats (15A).
Fuse arangements in fuse bracket/battery:
S162. Glow plugs (coolant) (50A).
S163. Fuel pump (FP) relay/glow plug relay (50A).
S164. Coolant fan control (FC) control module/coolant fan (40A).
S176. Relays panel interior (110A).
S177. Generator (GEN) (90 Amp.) (110A).
Generator (GEN) (120 Amp.) (150A).
S178. ABS (hydraulic pump) (30A).
S179. ABS (30A).
S180. Coolant fan (30A). Source(s): http://forums.tdiclub.com/showthread.php?t=122606 fame !

Below is a listing of which fuse corresponds with which circuit:

1 - 10 Amp - Transmission Controller, Gauges, Autostick
2 - 10 Amp - Right High Beam Headlight
3 - 10 Amp - Left High Beam Headlight
4 - 10 Amp - Radio, CD Player
5 - 10 Amp - Washer Motor
6 - 15 Amp - Power Outlet
7 - 20 Amp - Tail, License, Parking, Illumination Lights, Instrument Cluster
8 - 10 Amp - Airbag
9 - 10 Amp - Turn Signal Lights, Turn Signal/Hazard Indicator
10 - 15 Amp - Right Low Beam
11 - 20 Amp - High Beam Relay, High Beam Indicator, High Beam Switch
12 - 15 Amp - Left Low Beam Headlight
13 - 10 Amp - Fuel Pump Relay, Power Train Control Module
14 - 10 Amp - Cluster, Day/Night Mirror,Sunroof, Overhead Console, Garage Door Opener, Body Control Module
15 - 10 Amp - Daytime Running Light Module (Canada)
16 - 20 Amp - Fog Light Indicator
17 - 10 Amp - ABS Control, Back Up Lights, Daytime Running Lights, A/C Heater Control Cavity Fuse Circuits
18 - 20 Amp - Power Amplifier, Horn
19 - 15 Amp - Overhead Console, Garage Door Opener, Trunk, Overhead, Rear Reading, and Visor Vanity Lights, Trunk Release Solenoid, Power Mirrors, Power Door Locks, Body Control Module, Aspirator Motor
20 - 20 Amp - Brake Lights
21 - 10 Amp - Leak Detection Pump, Low Rad Relay, High Rad Relay, A/C Clutch Relay
22 - 10 Amp - Airbag
23 - 30 Amp - Blower Motor, ATC Power Module
24 - 20 Amp - Power Window Motors
25 - 20 Amp - Power Door Lock Motors, Power Seats

Fuse #8, #18 and #22.

Below is a listing of which fuse corresponds with which circuit:

1 - 10 Amp - Transmission Controller, Gauges, Autostick
2 - 10 Amp - Right High Beam Headlight
3 - 10 Amp - Left High Beam Headlight
4 - 10 Amp - Radio, CD Player
5 - 10 Amp - Washer Motor
6 - 15 Amp - Power Outlet
7 - 20 Amp - Tail, License, Parking, Illumination Lights, Instrument Cluster
8 - 10 Amp - Airbag
9 - 10 Amp - Turn Signal Lights, Turn Signal/Hazard Indicator
10 - 15 Amp - Right Low Beam
11 - 20 Amp - High Beam Relay, High Beam Indicator, High Beam Switch
12 - 15 Amp - Left Low Beam Headlight
13 - 10 Amp - Fuel Pump Relay, Power Train Control Module
14 - 10 Amp - Cluster, Day/Night Mirror,Sunroof, Overhead Console, Garage Door Opener, Body Control Module
15 - 10 Amp - Daytime Running Light Module (Canada)
16 - 20 Amp - Fog Light Indicator
17 - 10 Amp - ABS Control, Back Up Lights, Daytime Running Lights, A/C Heater Control Cavity Fuse Circuits
18 - 20 Amp - Power Amplifier, Horn
19 - 15 Amp - Overhead Console, Garage Door Opener, Trunk, Overhead, Rear Reading, and Visor Vanity Lights, Trunk Release Solenoid, Power Mirrors, Power Door Locks, Body Control Module, Aspirator Motor
20 - 20 Amp - Brake Lights
21 - 10 Amp - Leak Detection Pump, Low Rad Relay, High Rad Relay, A/C Clutch Relay
22 - 10 Amp - Airbag
23 - 30 Amp - Blower Motor, ATC Power Module
24 - 20 Amp - Power Window Motors
25 - 20 Amp - Power Door Lock Motors, Power Seats