Readings with different resisters
Here's some observations of this fix.
1st, the worry about reduced mileage and extra fuel consumption... Don't worry, I have some facts to back this one
Nope, no problem with extra fuel or reduced mileage. I checked in VAG-COM and also did before and after resistance readings. With the documented proceedure, the resister is in Parallel with the factory temp switch/sender. This means that the electricity will take the lowest resistance path. As the temp goes up, the switch/sender actually lowers the resistance, so the 10k or 4.7k ohm resister actuall get's ignored. When the switch is thrown, the temp goes down to the following, and right back to real temp as soon as released:
10k ohm = -15 degrees cel. Not necessary, too low and turns on glow cycle
4.7k ohm = 2.7 degrees cel. This is good, only starts short glow cycle
3.28k ohm = ~24 degrees cel. This is probably the best setting IMO. It doesn't cycle the glow plugs, but does modify injection timimg and starts real easy.
1.67k ohm = 56 degrees cel. on the warming up side.
Somewhere between 3.28 and 1.67 is where the ECU will stop considering the car cold and assist starting.
So, what I'm getting at is this, no codes with this mod, no lasting affects past the release of the switch after starting. So if you have replaced the temp sender, starter, battery and confirmed that your injection timing is good, and don't want to do any more with your pump, or fear that it's on it's way out, give this one a try
P.S. On the New Beetle, it's cleaner to splice the ECU side of the circuit. You can make it totally invisable and put the switch anywhere ya like.