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Thu Jan 16, 2020 3:21 am

Good morning everyone!
I'm hoping someone can help me figure out the issue with my glow plug indicator light on the dash. I've taken it to multiple VW oldtimer mechanics and they say that it just is what it is and there's nothing to do about it...but I was thinking the community here might have a better idea.
I recently had to replace all 4 of my glow plugs. They were not working at all, and the glow plug light on my dash was staying on for at least 3 minutes before it would switch off. I did not know what the issue was originally so I brought it to a mechnic in Vilnius, Lithuania. They didnt speak English well, and after leaving the van for a day they ended up replacing the relay with a cheap (I'm assuming) new relay and did not give me the old one. I got the glow plugs themselves fixed the next week, but now the light on the dash never goes out.
I usually count 30 seconds before starting, but the endless yellow light is not ideal.
Apparenlty the relay is fine, as well as the wires from the harness.
Does anyone have any idea or what would be causing this issue? It seems too much of a coincidence that it stopped turning off when a new relay was installed and work on the plugs was done.
Thank you for any and all information

Thu Jan 16, 2020 6:44 am

the glow plug relay for the 1.6 diesel has 7 contacts, the simple relay you had installed likely has 4. you need to replace it with the correct relay as it contains the temp sensor input and has a terminal for the glow plug light. here's a good article on the circuit and troubleshooting.
http://chris.chemidl.in/vw-diesel-info/cold-runnin...ug-system/

Thu Jan 16, 2020 7:08 am

My glow plug light use to go on for a while as well. One of the issues I had was the coolant temperature sensor on the head had a very dirty and corroded contact. This increased the resistance making the car think it was a lot colder than it was. Cleaning that up seemed to help.

Yes, check what relay is in there. I believe the T4s got different relays that T3s starting at a certain chassis number. Part number should be 171 911 261. Or it could be a 4 pin relay as suggested above.

Thu Jan 16, 2020 8:59 pm

He doesn’t say what year but its possible he has the early ‘slow’ relay but is using the later ‘fast’ glow plugs. That’ll burn out your plugs because they stay on way to long. I believe it is impossible to get the early plugs so you are required to get the newer relay. That’s what I had to do to my ’78 Rabbit.

Thu Jan 16, 2020 9:32 pm

It should also be noted that the dashboard light is not a true indication of whether or not (nor how long) the glow plugs are actually activated. Rather, the dash light is driven by a separate timer circuit in the relay.

To truly test glow plug operation, connect a test light to the glow plug buss bar and a good ground, and visible from the driver's seat. This will tell you whether/how long the glow plugs are being activated when starting the van, and during operation. This will provide valuable information in how to proceed.

Mon Jan 20, 2020 3:42 am

[quote="DanHoug"]the glow plug relay for the 1.6 diesel has 7 contacts, the simple relay you had installed likely has 4. you need to replace it with the correct relay as it contains the temp sensor input and has a terminal for the glow plug light.

i finally got the replacement relay order this morning and after install, light was out 30 seconds later. Thank you very much for the advice!
For the record it was a Topran relay #102 931 (for a cheap, 15-$ option)

Mon Nov 01, 2021 6:45 am

I have instead the opposite problem: the glow plug dashboard yellow light does not turn on anymore, after I changed the original night lights in the dashboard with new led lights.

This makes me think that, obviously, the problem has something to do with some connection in the dashboard but I have been extremely careful in reassembly the dashboard and the engine works just fine as before. So it must be some connection... but what??

What could it be? How do I find out?

Mon Nov 01, 2021 8:39 am

Luca-Waldo_Adventures wrote: I have instead the opposite problem: the glow plug dashboard yellow light does not turn on anymore, after I changed the original night lights in the dashboard with new led lights.

This makes me think that, obviously, the problem has something to do with some connection in the dashboard but I have been extremely careful in reassembly the dashboard and the engine works just fine as before. So it must be some connection... but what??

What could it be? How do I find out?
If you have the original 30+ year old foil printed circuit on the back of the instrument cluster, it can be damaged with something as simple as a bulb replacement. I would remove the instrument cluster and carefully examine for any minor damage.

Mon Nov 01, 2021 8:52 am

So you think it is the foil printed circuit. Then:

1) how to I inspect/find out if I damaged it while removing the bulbs?
2) can it be replaced? where do I find it?
3) I was instead thinking that is the yellow bulb/glow plug light that broke. Can that be replaced?

Mon Nov 01, 2021 3:28 pm

Luca-Waldo_Adventures wrote: So you think it is the foil printed circuit. Then:

1) how to I inspect/find out if I damaged it while removing the bulbs?
2) can it be replaced? where do I find it?
3) I was instead thinking that is the yellow bulb/glow plug light that broke. Can that be replaced?

I am by no means an expert, but I did clean and remove the colored bulbs from dash when I had it open. When you take the unit out, there are simple screws that can be removed from the backside so that you can access the bulbs.

It could also be the foil as mentioned. Sometimes the connections get worn out or scratched and the current can no longer travel to the bulb. If you take out the foil and just put it under a light, you'll be able to follow the electrical paths. Once you know the path to the yellow bulb it should be fairly easy to see if it is the foil or not

Finally, the bulbs are pretty easy to find on the vendor sites online, for quite cheap!