Tech Tips

Use this comprehensive information library whenever you need helpful hints from car repair professionals. Whether you are a professional or a DIY mechanic, you’re sure to find the tips you need to insure a job well done. Click here to go back to the previous page any time during your search.

Volkswagen

Glow Plug Circuit Quick Checks

Edited from an article by Larry A. Bailly, Import Specialist Contributor, ImportCar Magazine, September 2005

Two types of glow plug circuits were used on early and late model vehicles. The slow glow system was installed on early production vehicles; the fast glow on late production vehicles. Always refer to the relay number for proper identification.

The relay number for early slow glow plug circuits is 321-911-261 (BWC #203-0024). The later relay glow plug relay number is 171-911-261 (BWC #203-0023). Note that the relays must match the proper part number for the type of glow plug that is installed. An incorrect match of fast glow relay and slow glow plug will result in premature failure of glow plug and/or relay.

To quick check the system, check the amount of current that is flowing to all glow plugs. A good specification to remember is fast glow plugs pull 12 amps each and slow glow plugs pull 9 amps each.

Listed below are some guidelines to refer to when checking fast glow plug systems.
48 amps - all glow plugs are operating correctly.
36 amps - one glow plug is defective.
24 amps - two glow plugs are defective.
12 amps - three glow plugs are defective.
0 amp - all glow plugs are defective.

The above specifications are applicable to four-cylinder applications. If you have more than four glow plugs, just add 12 amps for each fast glow plug and 9 amps for each additional slow glow plug. 

NOTE: Depending on outside temperature, you may experience a surge of current up to 140 amps.

Source: Ed Hefner, Sr., Training Coordinator, Vehicle Performance Techline, Engine Systems Learning Center.

Go back