[Vwdiesel] Glow Plug Indicator Light

Sandy Cameron scameron at storm.ca
Fri May 30 07:17:42 PDT 2008

At 09:50 PM 29/05/2008 -0400, you wrote:
>Once again, returning to my favorite group of people to help me solve a
>My 81 recently started doing a peculiar thing.  The yellow glow plug
>indicator light will light when the ignition key is turned, but will NEVER
>turn off until the engine is started.  The engine will start (even in cold
>temperatures) in the usual manner if I wait for a period of time equivalent
>to the time in the past when it was functioning properly.  After the engine
>is started, the yellow indicator light will turn off.
>It acts the same way even if the engine is at normal operating temperature
>and I perform a restart.
>I replaced the glow plug relay with a new one and it did not fix the
>condition.  Any suggestions?

Good description of symptoms and leads us directly to failure of the engine
temp. sensor or its wiring.

On older cars, this was a single wire sensor, BLUE/White wire, and clipped
on to the sensor with an exposed, flimsy clip, and depended on the aluminum
hose spud for electrical ground.

 Later engines (A2s) have plastic hose spuds and require 2 wires for each
sensor, and a 2 pin plug.

The sensor was located either on the heater hose exit at the rear end of the
head, and later, in the rad hose exit fitting on the front (side?) of the head.

Grounding the blue/white wire should cause the glow relay to short-cycle, no
yellow light, or very short cycle.

If grounding the wire causes a short cycle, the problem is the sensor or its
grounding, if no change, the wiring is faulty.

Open circuit should result in long  (2 min) cycle or until starter is
actuated, which terminates cycle.

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