The Webasto heater as standard in the A2 isn't a cabin heater (night heater) as used in trucks, it's an additional heater that warms the coolant when the engine is running.
The A2’s diesel engines are very efficient, and when outside temperatures drop it can take a substantial time for the coolant to rise to normal operating temperature of 90°c with engine heat alone. At ambient temperatures lower than 5°c, and when the coolant temperature is lower than 72°c, the Webasto works to help bring/keep the coolant temperature around the normal working range.
In colder climates the same heater is modified to run without the engine running, and a by-product of this is it can be used to pre-heat the cabin. This is achieved by fitting an in-line electric water pump to circulate the water in the cooling system, and various electronic sensors and switches that allow this function to be timed or turned on via a remote fob. The electronics can power up the climate control unit, and as the coolant heats, the cabin warms.
The glow pins that are used in the Webasto’s fitted to A2’s are specific to the Thermo top C and Z variants. As you’ll probably know, there are many manufacturers of such devices, and the specs vary accordingly.
Silver 2002 1.4 TDi SE
Red Sports Leather, TTS FBMFSW, OSS, Bose, RNS-E with Audi Bluetooth Telephony & SDS, DIS, Audi iPod link, Cruise Control, Komfortblinker, Rear Cup Holders, 4 x Electric Windows, Auto-dimming Rearveiw Mirror, A2OC Mats, TT Pedals, Puddle Lighting, Headlight Washers, Headlight Protectors, Debadged, 0.659 5th Gear , Whiteline Rear ARB, Koni FSDs & Weitec -30 Springs, 17" TT Ronal Wheels with 215/40 Tyres, Floppy Wiper, Votex Body Kit, Spacesaver, Heated Wing Mirrors, K&N, Stealthed & a Coat-Hanger!