Tdi clicks on cold start - Volkswagen Cars & Trucks

Not sure what "tick over" means. Suspect it is hard to start when cold? Could be bad glow plugs. They "warm" the cylinders to get them up to temp before starting. It could also be that you are not waiting for the cylinders to warm up. I have a 2009 tdi. It has a light on the dash that goes on when I put the key in, but I have to wait for it to go out before starting the engine.

02 VW Jetta GL TDI
WON'T start or HARD start as in takes alot of cranking over to finally start eventually

It's diesel. Diesel engines do not like cold, but that is normal. I am going to assume this engine has a start delay in cold weather to allow for Glow Plugs to warm up the cylinders before actually turning over the engine. I don't know about TDI's specifically, but I think a TDI Mech at your local Volkswagen dealer could confirm my assumption. They may call the parts something different, but the function will be the same. Sounds like normal operation for a diesel engine in cold weather...obviously, this would be why the engine always turns over immediately in warm weather...no need for the Glow Plugs to warm the cylinders. Best of luck resolving this problem.

fix the fuel leak first that can cause hard starting and black smoke

Replace your Glow plugs.

There is a 5th injector called the cold start injector, that is electrically controlled off the starter. You can easily unscrew it while still attached to hoses and wires, and watch it squirt. You can also verify it is getting voltage with a test light or meter. There is also a thermal timer for it that could be bad and preventing current from the starter.

Your Jetta has a block heater available. It plugs in and keeps the block warm, making it easier to start. Below is a link with step by step instructions for battery replacement.

01 Jetta Battery Replacement

yes glow plugs have a lot to do with engine having tough
time in cold weather. before replacing glow plugs
check relay and fuses.

you may have a dampner issue with your climate control. the dampner is controlled by your Hot/Cold switch. if the dampner is stuck or not working you won't get one but the other. in your case maybe the dampner is stuck on hot, even tho the control says cold.
one possible solution may be a fuse... talk to a volkswagon guy and he'll be able to offer a suggestion or two.

vacuum to blend doors cancels when engine uses it upon acceleration... there is a check valve that could have failed there at vacuum lines to blend doors .good luck