2006 jetta tdi, ambient temperature location? my a/c quit working and i have no power at the compressor plug, it is up on charge, the dash temperature sensor quit working this winter, this not reading correctly could cause this? thank you, Sam

This problem is with ecu / ecm= engine control computer. These are a common and horrible problem on vw's, particularly on tdi's. The signs in a tdi are when car dash lights come on, but no glow plug light,trans gear lights flash, but car still tries to crank. And hopefully ecu has enough power to out out code u0100= no communication with ecu. Unfortunately the ecu will need to be replacd. The ecu is located under the hood, near and under the wipers. Used ecu with same codes run $50-200. New $1000. If get used one make sure has a return policy. codes must match production quarterly year.

possibly a bad expansion valve/orifice tube. or the blower switch isn't working properly. I mean, not moving the blender door correctly, not letting air flow through the A/C evaporator!

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On drivers side of dash. The edge that would be covered by door when it is closed. There should be a picture in you owners manual. There is a small cut out on bottom that you stick a screw driver in to pry open.

you are low on gas so it will not click on as the gas is also the lubricant ,this vehicle should hold about 700 grms of gas

The problem is the temperature blend door. Very costly to fix. I have a 2003 with the same problem. A diverter flap door that allows it to switch over from heat to air, is broken. The part is 400.00 and the labor itself is 800.00. The whole dash needs to come off. Everything is behind the dash. Sorry!

Does your glow plug light on instrument panel come on when you turn the key? I'm assuming the car won't start? If no GP light on instrument panel then it sounds like a Relay 109 problem. It's the main power relay. It's a grey or black 1" square relay located under the dash on the driver's side. Give it a smack with a screwdriver or something. You might be able to knock it back into whack. Seriously.
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How to remove a coin from CD slot in VW Jetta 2006 tdi

sounds like you just have a loose alternator belt and since the system takes longer the light s tay oon until the alternator starts charging the battery by then the engine is already warnmed uyp

Yes you can get a shorter belt and bypass the ac. It may be as simple as going to the parts store and tell them you have 2001 jetta no ac. Just keep the receipt.
You should also disconnect the a/c compressor connectors/wires/plugs also, try doing this before you bypass the ac first incase doing so gives you warning lights on the dash board.
Also know that the defrost setting uses the a/c so it will take longer to get the condensation off the inside of the window.