Check glow plug system

Two types of glow plug systems are used on VW and Audi diesels, the normal glow system and the quick glow system. Testing procedures are the same for both but parts from one type of system must not be used in the other type.

Testing procedure

• Check the glow plug fuseable strip on the firewall in the engine compartment. Replace the fuse if it is burnt. If the fuse burns repeatedly, there is a short in the system which must be repaired before further testing.
  
• Disconnect the blue and white wire from the temperature sensor on the cylinder head. This will allow the glow plug relay to stay energized for the maximum glow time.
• Connect a test light between #4 glow plug and ground.
• Turn the ignition key to the glow position.  If the test light lights and stays on for:Quick glow system = 15 seconds (min.)
  Normal glow system = 90 seconds (min.)
  test the glow plugs.   If the test light does not light, first test the glow plug circuit, then the glow plugs.
• If the test light lights, but the minimum glow time is not reached, replace the relay and retest.

Check glow plug circuit

If the test light does not light:

• Reconnect the blue and white wire to the engine temperature sensor.
• Remove the glow plug relay.
• Connect a voltmeter between the following terminals at the relay plug on the fuse panel

If any of the test results are incorrect refer to the applicable wiring diagram and repair the problem (wiring or connections).

• Connect a jumper wire between terminal L and ground.
• Turn the ignition switch to the glow position.
• Glow plug indicator light should come on.

Connect an ohmmeter between terminal T and ground to check the temperature sensor.

If the resistance is out of this range check the sensor wiring and
connections. If they are o.k., replace the sensor.

If a problem is found and repaired, recheck maximum glow time.

If all test results are o.k. but the glow plugs still do not receive power, replace the glow
plug relay.

Check glow plugs

Connect an ammeter to the power lead for the glow plugs.
Turn the ignition key to the glow position.

Initial current draw may be as high as
140 amps but will stabilize to a steady
value after a short period of time.

Quick glow system (brass nut)
Each glow plug draws approximately 12 amps

Normal glow plug system (sliver nut)
Each glow plug draws approximately 9 amps

To locate bad glow plugs disconnect the bus bar from the glow plugs.
Connect a test light between the battery positive terminal and each glow plug.

• If the test light lights, the glow plug is o.k.
• If the test light does not light the glow plug is bad and must be replaced.

Note:
If the glow plug tip is worn away, check the spray pattern of the injector and replace the injector if necessary.

 

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