On my 2000 Volkswagen Passat my heater and Ac control unit is not working. What could it be?

SOURCE: no dash lights

possibly. i would get the wiring checked out by an electrician.

hope this helps.

SOURCE: 2000 Dodge Caravan Sport. Heater and AC quit working.

these heater control units were in a bad spot..cup holder right below..coffee spills have been known to get in control unit..can be expensive to replace..try a wrecking yard

SOURCE: 2000 AC CIRCUIT FOR NEW VW BEETLE

Check fuse on top of battery.

SOURCE: 2000 lincoln LS AC blowing hot air i've replaced t...

You need a scanner to diagnose,not a code reader.

The DATC Module ( Dual Automatic Temperature Control Module) is a possible

SOURCE: How to replace bulbs for ac/ heater control unit

1. Remove the dash around radio (just clips)
2. Remove 2 screws pointing up . (You do not need to remove screws which are parallel to the floor)
3. Remove screw pointing up on the bottom of the dashboard on left side of the driver (near left leg).
4. Remove 2 screws pointing up in the instrument cluster area.
5. Put car in 1st gear and gently remove black plastic surrounding instruments (it will have ait vents, so slide it carefully out not to damage foam insulation on air ducts; start on the bottom hear steering column) ; unplug connectors to clock and emergency flashers.
6. Remove 2 screws, now exposed, near instrument area, holding dashboard. (that was what I spent most time on, I didn't know about this screws.
7. Now gently remove (or move up) dashboard (around instrument cluster and heating controls.) Start next to ignition (careful not to damage the bulb next to the ignition.
Since you only need to get to the heating controls block, I only move up the dashboard next to it.
8. Remove 2 screws that hold the heating control and slide heating control out . This step is unnecessary If you totally removed the dashboard.
9. Pull out lever controls for fan speed, zone and temp
10. Use the screwdriver (flat) to pry 2 plastic tabs on top and on the bottom of heating control so black cover can be remover.
11. You did it! two bulbs are going to be under the cover.