NO glow plug light???

[tkisling]

Since i bought this car the glow plug light has never came on. the relay doesn't shut off either and I know I need a new one. But why question is what is causing the glow plug light on my 81 diesel Rabbit not to come on? I replaced the yellow LED for the glow plugs in the cluster with a new 5mm green one from radioshack and still haven't had any success.

[Baron VonZeppelin]

I'm guessing you have the Gplug relay disabled - since it doesn't shut off. Or do you let the Gplugs continually cycle ?

The relay triggers the indicator when to come on and go off - but you probly know the operation of the indicator is not directly related to the operation of the Gplugs.

Did you check the yellow LED after you removed it ?
If it still glows with voltage applied - its okay.

I would try taking the relay in and out about 6-10 times to try and see if the contacts needed some disturbance to get better contact - and kinda tap the relay on a piece of wood in a few diff ways - and see if anything wakes up afterwards.

[tkisling]

No luck with the yellow LED and looking at it with a magnifier the internals appear to be cracked. I also tested the duplicate green LED and t seems that it only works one way in terms of the terminals. So maybe i just have to flip the green LED I installed in the cluster around

[Baron VonZeppelin]

Worth trying i think.
Most LED's are polarity sensitive, as in work one way and not the other. Good luck with it being the fix.

[tkisling]

Ok, I reinstalled the LED the other way around and nothing happened when I switched the key on. BUT I connected terminal L of the glow plug relay socket to ground and the light came on. This was the first test in the Bentley manual for the GP light. The next step wants me to disconnect the red/white wire from the temp sensor and ground it to see if the GP light will turn off. Problem is, my 81 rabbit has TWO wires going to the temp sensor, one is light blue and one is light blue/light green. Which is the one I disconnect??? The only red/white wire I see on the GP circuit is connected to the glow plug rail. Is it possible the GP relay is causing the light not to come on even though it supplies power to the glow plugs??

[Baron VonZeppelin]

Is it possible the GP relay is causing the light not to come on even though it supplies power to the glow plugs??

Yes.

I'm thinking both of my coolant temp sensors (each coolant flange has a sensor - front of head and side of head) on my 81 has a light blue wire.

Could check tomorrow.

But pull them all off both the coolant sensors one at a time - and ground them one at a time - and try to complete the test.

[Vincent Waldon]

Is it possible the GP relay is causing the light not to come on even though it supplies power to the glow plugs??

Completely... different part of the circuit within the glow plug relay and the LED is not related to whether power is being applied to the glowplugs... its a "wait till I go out before you start" signal.

[tkisling]

I got all my blue wires mixed up now and can't remember where they go. Can you guys help me put them in their place?  I have a light blue, light blue/green, and a light blue/black wire.

[tkisling]

Never mind, i got figure d out and stuffs working again. But I'm still confused as to why my GP light doesn't come on.

[Baron VonZeppelin]

More than likely, its because that portion/circuit of your Gplug relay is dead.

Since the test you did by Bentley made it come on, its most likely a problem in the relay.

Your car would have came with Slow Gplugs and Slow Gplug relay.
The Slow relays are becoming hard to find New.
I've seen a guy on eBay in recent past selling the Slow relays, New for about $20-25.