Author Topic: Glow plug light comes on while driving (Read 13474 times)

rabbitman · « **on:** April 04, 2008, 06:06:17 pm »

I have a problem, starting a few days ago my glow plug light started flickering and now quite frequently it comes on steady. This is on a mk1 so there's not supposed to be a water sensor. Is this a bad GP relay? The glow plugs and relay act normal when it's cold started, you know, light goes out and 5-10 seconds later the relay clicks. I don't hear the relay click when the light comes on while I'm driving but there's road, wind, engine noise and CD playin' to drown it out. :lol: Anyways, when problems are had, this is the place to go.

PS. It always scares me when the light comes on 'cause I've heard of the plugs burning out :shock:

Quantum TD · « **Reply #1 on:** April 04, 2008, 06:45:32 pm »

Either:
1) bad relay
2) bad sensor
3) water on the fuse panel
4) bad contacts on main glow fuse

Good luck

TPW · « **Reply #2 on:** April 04, 2008, 07:56:50 pm »

The light comes on when the relay connects to a ground. If the wire between the relay and the light has a bare spot that grounds out, that could also cause the light to turn on.

subsonic · « **Reply #3 on:** April 04, 2008, 08:59:47 pm »

Water fuel seperator. If you still have it, it's time to drain.

fatmobile · « **Reply #4 on:** April 04, 2008, 11:18:28 pm »

I've had the glow plug power wire connector get loose,
one of the fat red wires on the positive post of the battery goes to the glow plugs, the lug was loose.

burn_your_money · « **Reply #5 on:** April 05, 2008, 06:41:55 am »

Quote from: "subsonic"

Water fuel seperator. If you still have it, it's time to drain.

This one happened to my old jetta

rabbitman · « **Reply #6 on:** April 06, 2008, 10:15:13 am »

Wow, you guy are really on top of things

So far I've swapped the wires on the temp sensors and the guage works like normal and the GP light still flickers sometimes.
How do I get to the water seperator? I've looked up above the right rear tire and I can't see anything and it's not under the seat......at least it's not obvious.

Ps. We went snowmachining yesterday at the only place that still has snow......wow that's fun, my poor 'machine is havin' a rough life. :twisted:

subsonic · « **Reply #7 on:** April 06, 2008, 12:09:32 pm »

Right side, in front of rear tire, up under the body.

blkboostedtruck · « **Reply #8 on:** April 06, 2008, 12:21:08 pm »

he has a MK1 it should not have a seperator! only seperates water in the filter under the hood! am i right?
Duane

subsonic · « **Reply #9 on:** April 06, 2008, 12:38:44 pm »

Not sure, you may be right. My bentley only goes back to 85. Did the mk1 have a high water indicator?

rabbitman · « **Reply #10 on:** April 06, 2008, 02:38:57 pm »

I just looked in my bentley and there is a gravity valve and a expansion tank, wasn't sure if the expansion tank doubled as a water drain but it doesn't say anything about it. I can't find it anyways. :roll:

burn_your_money · « **Reply #11 on:** April 06, 2008, 03:37:11 pm »

You're right Duane. There is no water separator, only the fuel filter.

Vincent Waldon · « **Reply #12 on:** April 06, 2008, 09:41:31 pm »

If you had one, it would look like this:

zukgod1 · « **Reply #13 on:** April 07, 2008, 07:22:50 am »

I just had this happen this morning, light flicker but very dim and then it stayed on but still very dim. Pulled the relay and still on.

I'm kinda leaning towards the 2 wires that used to go to the water separator. I just cut them off when I removed it. I suppose there could be moisture causing them to conduct a tad??

I'm at work now so I wont be able to look till tonight

Anyone have a suggestion before I start looking?

Vincent Waldon · « **Reply #14 on:** April 07, 2008, 09:04:40 am »

Quote from: "zukgod1"

I just had this happen this morning, light flicker but very dim and then it stayed on but still very dim. Pulled the relay and still on.

I'm kinda leaning towards the 2 wires that used to go to the water separator. I just cut them off when I removed it. I suppose there could be moisture causing them to conduct a tad??

BTDT, about a hundred times... the PO had deleted the wiring to the water separator but water seeped into the electrical tape... little bitta water, some road salt... after all, those leads do go straight to water detection probes so it's a sensitive circuit.

Cut the wires back a bit, retaped and isolated them from each other by a few inches... no more dim and/or flickering glowplug light.