If you've had difficulty identifying what is causing a persistent glow-plug fault in your TDI, use this kit to replace the glow plugs and harness. It includes an original equipment harness from VW and a set of four Bosch glow plugs (original on many TDIs).
This kit fits all A3 and B4 TDIs, and A4 TDIs through 2001. If you're not sure which harness you have on your A4, look at the existing harness. If it has two wires coming out of the shielded portion connecting to the glow plugs, this kit is for you. If it has four, look for the Late A4 ALH glow plug and harness kit.