cold weather starting problems

I have read the treads on cold weather problems and not found answers to my issues. Our 96 Passat TDI was parked outside for 2 days at nightime temps close to O F. I had to leave jumper cables hooked up for almost 45 minutes before I could get it to start. So...
1. From my research no plug-in heater exists for 96 Passats. (I asked zerostart folks as well). Am I wrong?
2. The magnetic stick-on heater I bought is suppoed to go on bottom of oil pan but the bottom of engine has a cover on it. Where do I attach this heater? How long do I leave it plugged in?
3. What are other options for getting started in cold weather aside from fuel additives?
Thanks
shamu

Those magnetic stick on heaters are mostly worthless. They are generally about 100 watts - you need much more. The tdiheater is (I think, I don't have one) 1000-1500 watts. That is 10 times the heat, and it still takes a few hours to warm the engine.

A stick on heater will help only if you plug it in first thing when you turn the (warm) engine off. Even then they won't hold your more than overnight.

Your best bet is to replace your battery. TDIs need more power to start than a normal car, even the bigger battery will not last near as long. Glow plugs take power, which a gas car won't have. Then the higher compression needs more power to crank the engine. Diesels also need to spin faster than gas to start. The final straw is cold - your battery has the least power when things are cold.

If you have good jumper cables, the engine should start just fine even without a battery. (Don't try this, there are many dangers in this setup, just saying it should work). Get some better cables - once again, your TDI needs heavier cables than a gas car.

Also check your glow plugs. They do burn out once in a while. (This should set a code, but check them anyway).

I agree with Hank...

I expect when you tried to start it, it either did not turn over, or did so slowly, so you hooked it up for 45 minutes to charge it ?

This being so, I would expect your battery is on the way out. A good battery would easily have plenty of cca ( cold cranking amps ) to start at that temp unless you left your lights on or there is an electrical drain with the car off. If you have a dvm ( digital volt meter ) you can do a rudimentary test with the car off. A good battery should be 12.6-12.8 volts DC ( car off ). You can check the charging system with car at idle, the reading should be 13.5-14.5 volts; however, the best way to go is have the dealer hook it up under load to test everything.

Adding a coolant heater will make starts a tiny bit easier on cold mornings and provide heat to the cabin quickly, a lot of people here love them....