No glow plug light ONLY when cold (still starts)

UPDATE 6/3/16: SEE POST #56 for the solution.

Since it's started getting colder, my glow plug light doesn't come on when I turn the key (doesn't even flash the 1/2 second). However, the car starts up okay (the colder it is, the more cranking it takes, but never more than a few seconds) after the car starts and runs for a while, I can shut it off; then, when I turn the key again (engine still warm), the glow plug light flashes as it normally should. Today, it's about 50 degrees, and when I went out, I turned the key on and off about ten times to see if the light would ever come on, but it didn't, so I cranked it, and the car started almost immediately. I let it run for only a few seconds, shut it off, turned the key, and the light flashed on.

I have the following codes:
- 01117
- 00626
- I used to get 00525, but not since I got the new Relay 109

I've replaced the following:
- Relay 109 in October
- Relay 180 in June
- 50A fuse in June

I've tested the following:
- Resistance for all four GPs is the same, around 1.0
- Unplugging the coolant temp sensor causes no change
- The GP light bulb on the instrument cluster is good
- I can't test the voltage at the harness - the Glow Plug 101 tutorial doesn't account for the light not coming on, so testing this will only tell me the obvious: there's no voltage when the light doesn't come on.

I really tried and tried to find the solution to this without starting the millionth new thread on glow plugs, but I just can't figure it out (see also http://forums.tdiclub.com/showpost.php?p=3575669&postcount=1270 and http://forums.tdiclub.com/showpost.php?p=3594454&postcount=1289
for my posts on the Glow Plug 101 thread, which unfortunately does not seem to contain my solution)

A resistance test on glow plugs is not 100% accurate. If you want to test them without removing the glow plugs (and watch them glow), remove the harness and measure the current to each glow plug. It should draw approx 16 to 18 amps when power is first applied, and drop to around 10 amps after about 10 seconds.

I bet your relay 109 is going out. It will likely leave you stranded one of these "cold" mornings when the shaking of the engine isn't enough to allow it to make contact.

rdkern said:

I bet your relay 109 is going out. It will likely leave you stranded one of these "cold" mornings when the shaking of the engine isn't enough to allow it to make contact.

Click to expand...

Sorry, in trying to shorten the message, I took out an important bit. I don't believe the problem is the 109, not only because I just got a new one last month (I've only taken the car out twice since then), but also because I never have any trouble starting the car. Every post on this forum about the 109 lists as symptoms 1. that the GP light doesn't come on and 2. that the car just does not start.
When I replaced the 109, it seemed at first to solve the problem, but I am not so sure now. When I put it in, I immediately got a GP light to flash on and off as it should, but the next time I took the car out (a few weeks later), the no-GP-light problem was again present. At this point, I determined that the problem was only present when the engine was cold. I am not sure if that was the case before I replaced the 109.

I think you have an electrical issue. When the gp light doesn't come on, the ecu usually isn't "awake". Plug in VCDS to see if you have any info coming from the ecu on these cold mornings. If you do, then perhaps you have an issue with the light itself not making contact when cold, and the harder-than-normal starting could be timing.

Other item that I would do is to clean, tighten all grounds. And since you have a spare, keep the 109 handy just in case.

I installed a new harness and four new glow plugs, and there is still no change (i.e. the GP light still doesn't come on, and I can still start the car).

rdkern said:

When the gp light doesn't come on, the ecu usually isn't "awake". Plug in VCDS to see if you have any info coming from the ecu on these cold mornings.

Click to expand...

I don't have a VCDS. How can I check the ECU? If all the other instrument cluster lights come on, is that a sign that the ECU is doing its job?

rdkern said:

Other item that I would do is to clean, tighten all grounds.

Click to expand...

Which grounds would we be talking about here? I don't really understand what that means. Sorry. Electrical stuff is a mystery to me for some reason.

The grounds that cause all sorts of issues are here and there in the engine compartment and elsewhere. Two rather important ones, at least in the Passat, are on either side of the boost tubing, near the battery and windshield washer fluid. One post has about 4 grounds on it, the other has 2 iirc. There may also be one up kinda near the ecu box. It may not hurt to check and clean the harness that goes to the ecu.

And checking to see if you're getting power to the plugs when the light is not on might be interesting as well. Do you hear the gp relay click when you leave the key on for 20 seconds on a cold day? I'm wondering this since it appears you are getting power to the ecu, but somehow, in cold weather, the light isn't working. Bad ground on that light that is "fixed" in warmer temps? Interesting problem. I'll be following your progress.

It is very odd that the gp light does not come on when cold.

rdkern said:

Do you hear the gp relay click when you leave the key on for 20 seconds on a cold day? I'm wondering this since it appears you are getting power to the ecu, but somehow, in cold weather, the light isn't working.

Click to expand...

No. It doesn't click.

I looked at a few grounds under the battery tray and one on the block. They all seemed nice and clean (I run veggie, and my previous four cars were coated in veggie oil - this is my first clean veggie car, so I can't imagine dirty grounds being a problem here but not in the others).

I also inspected the ECU harness, and it was also clean.

I don't know what else to do. Maybe I'll try blowing some hot air on different parts and seeing if I can figure out what it is that needs to be warm in order to get those GP's to come on.

Thanks for your help.

Pull out the glow plug relay, wrap some thin stranded wires around the terminals and break them out, plug relay back in and start taking voltage readings on all pins to see what is going on.
You'll need a wiring diagram to know what pins do what.

mikerancourt said:

I looked at a few grounds under the battery tray and one on the block. They all seemed nice and clean......

Click to expand...

Generally, looking at the grounds tells you nothing. It is amazing what, in some cases, happens when you remove the nut, take off the grounding wires and clean them, then reattach nice and tight. It doesn't always fix stuff, but it does often enough to be worth the 1/2 hour it takes to do this task.

dieseljunkie said:

Pull out the glow plug relay, wrap some thin stranded wires around the terminals and break them out, plug relay back in and start taking voltage readings on all pins to see what is going on.

Click to expand...

I love this idea. I tried it immediately and ended up burning my hand a tiny bit and having a hot wire start to cut its way into the plastic casing of the relay. It was my fault completely. I'll try again with some properly insulated wire later today. Thanks.

rdkern said:

Generally, looking at the grounds tells you nothing. It is amazing what, in some cases, happens when you remove the nut, take off the grounding wires and clean them, then reattach nice and tight.

Click to expand...

That is what I did, actually, though my definition of "clean" is probably not as effective as yours. I'll try again and make sure I find more grounds. Thanks.

[FONT=&quot]I rigged up a test light to the GP harness (to each of the wires leading to it, first one, then the other), and it turns out I am getting power to the plugs after all. Thanks to the suggestion that I rig up thin wires to the blades on the relay then plug it in and start testing voltage, I was able to (if I understand the wiring diagram right – I’m looking at the one in my Haynes manual), determine that the relay is working. Well, I think so, anyway. For the first time I can recall, I was able to hear the relay click on when I jumped 30 to 87 (closing the circuit). Then, when I turned the key, I magically heard the click, as well. Maybe I just couldn’t notice it before, but I thought there used to be no click. Anyway, to be clear, that click is the sound of the relay doing its job and sending power to the glow plugs harness.[/FONT]
[FONT=&quot]I am having trouble reading the wiring diagram, so I don’t know which wire is responsible for sending power to the GP indicator light in the instrument cluster (I know that it is 17C in the diagram, but I don’t know how to find 17C on the cluster harness, nor do I know if it’s something I can test while spliced into the relay.[/FONT]
[FONT=&quot]I tested the bulb again, and it is good, so there is something else amiss. I don’t know why my indicator light isn’t going on, but at least I know the plugs are getting power.[/FONT]
[FONT=&quot]Two things are of note here:[/FONT]
[FONT=&quot]1. [/FONT][FONT=&quot]I clearly messed up by not testing the harness for power (I did do that on my old harness when I first started pursuing this problem, but not on the new one – perhaps I just failed to test the old one properly, or perhaps the new harness fixed one problem but not the one that’s specifically related to the light not coming on).[/FONT]
[FONT=&quot]2. [/FONT][FONT=&quot]The actual glow time is about four seconds (it’s about 45 degrees here). I think my slightly hard starts were the result of not waiting long enough, not knowing that the glow time is more than a few seconds (though no start since adding the new harness has been in very cold weather, and no start was very rough, anyway).[/FONT]
[FONT=&quot]3. [/FONT][FONT=&quot]I should mention that I have also found in recent weeks that both of my instrument cluster back-lights are blown, as well as my side marker lights. Could all of these bulb problems be related? I know the side marker lights are connected to the back lights, and of course the whole cluster uses the same ground. Could that be something I can or should check out? The wiring diagram says the ground to the cluster is E131, but I have no idea how to figure where that is in real life or where it actually connects to the frame. Any suggestions?[/FONT]

Sorry I didn't give warning to not short anything out with testing the glow plug relay. I thought that was obvious. You need to check for voltage at the glow plug harness (all 4 sockets). Then you want to verify that all your glow plugs are glowing by taking them out and connecting them across the battery. Warning! Don't burn yourself. If you are getting voltage to the harness and all your glow plugs are fine, maybe you didn't seat the harness all the way onto all 4 glow plugs? That harness is a dumb design. You really have to push hard to seat the connections. The whole glow plug system design is dumb. How did you test the glow LED in the cluster? It's not a bulb.

Here's a wiring diagram for a 96 Jetta TDI. Not the same year as yours but may be representative.

http://www.haywood-sullivan.com/vanagon/TDI/1996_Jetta_TDI_wiring_LONG4.pdf

dieseljunkie said:

Sorry I didn't give warning to not short anything out with testing the glow plug relay.

Click to expand...

I knew the risks.

dieseljunkie said:

Then you want to verify that all your glow plugs are glowing by taking them out and connecting them across the battery. Warning! Don't burn yourself.

Click to expand...

Thanks. I really don't know if I am going to do this. My plugs are brand new and replacing them didn't change a thing.

dieseljunkie said:

That harness is a dumb design. You really have to push hard to seat the connections. The whole glow plug system design is dumb. How did you test the glow LED in the cluster? It's not a bulb.

Click to expand...

It is actually a bulb. I've taken it out and put a + on one side and a - on the other a hundred times. It glows every time.

mikerancourt said:

It is actually a bulb. I've taken it out and put a + on one side and a - on the other a hundred times. It glows every time.

Click to expand...

Interesting...On the Passat's, they are LED's.

I would look closely at the instrument cluster. Particularly at this point n your troubleshooting, I suspect the issue is more in the cluster than the ECU.

Tony

I did a lot of fun work this morning:
1. I took out the cluster and took it apart to visually inspect and mechanically test all the connections working backward from the bulb to the cluster wiring harness. I had no problem with the ground when I applied 12v to various places along the circuit on the board leading up to the GP light, and when I applied 12v to pin 20 on the harness connector, I got a light. This means the cluster is in working order. I get no voltage at pin 20 when I turn the key, so it looks to me like the problem is in the wiring from the cluster to the fuse panel unless I'm failing to understand the whole circuit somewhere. Unfortunately, there are about 15 white wires bundled in that harness, and they disappear behind the fuse panel. I don't see how I could possibly get in there to try to figure out which wire is #20 (GP light) and trace it all the way to its source.
2. I did test the voltage at each of the four sockets on the GP harness, and I got 12v at each. I also made sure they were all snugly connected. They were.

To be clear, I can live without a GP indicator light. I am satisfied that the plugs are glowing and that the car will start even if I find myself in very cold weather. I've thought of a way to rig up a indicator with a wire spliced into one of the wires leading to the GP harness, then run through the firewall and spliced into wire #20. This will not, however, solve my code error (00626) and my CEL. I don't think I would be able to pass inspection next time around (I don't know when that would be since I've never owned a new enough car to need one) if I have a CEL (though maybe I can do it in the summer, and maybe the light will work normally in warm weather). So, how should I go about figuring out this wiring situation? Is there actually something I don't know about this circuit that might make the solution easier than taking apart every damn piece of the mess under the dash around the fuse panel?

Thanks for the great help, folks.

I don't have the diagram in front of me....

Does the ECU generate the signal to the GP light in the cluster?

Does the ECU sample the GP voltage, AFTER the fuse and/or relay? Then set a code, if it doesn't see the GP voltage?

Tony

TonyJetta said:

Does the ECU generate the signal to the GP light in the cluster?

Does the ECU sample the GP voltage, AFTER the fuse and/or relay? Then set a code, if it doesn't see the GP voltage?

Click to expand...

Strangely, I really don't know how the ECU is involved. Here's the wiring diagram:

You can see (if the image is clear enough for you)) that the only ins and outs to the circuit in the diagram are grounds and two other things not in the the picture (3/C5 goes right to the bulb and 3/J4 goes to the coolant temp sender).
So, I don't know what the ECU does in this or how/when it samples voltage.

OK so it's a bulb in your 98 Jetta. I must be confusing it with the LED in my IDI Jetta. I can't remember if the Passat TDI's have a bulb or LED for the glow indicator.

If you want to rig up a glow indicator, do it from the glow plug relay (wrap a wire to the output terminal).

This should help in tracing the wires from the cluster to everywhere else.

http://www.a2resource.com/electrical/CE2.html

Afaik, the ECU looks at the coolant temp sensors and glow plug current consumption to control the glow indicator duration and other signaling method. It may flash the indicator or not glow it if one or more glow plug is not drawing current (I am not exactly sure about this).

dieseljunkie said:

If you want to rig up a glow indicator, do it from the glow plug relay (wrap a wire to the output terminal).

This should help in tracing the wires from the cluster to everywhere else.

http://www.a2resource.com/electrical/CE2.html

Click to expand...

Which is the output terminal? This schematic says "Pin 9," but I don't see how to determine which is pin nine without removing the whole fuse panel and getting close enough to read on there if it has the pins marked. The diagram at the top of the page doesn't show what the panel actually looks like since not all blades are the same size or in a neat grid as in the picture.

I just realized that everyone may have thought I was testing my GP relay 180 before (doesn't actually say "180" on it, but rather Bosch 0281003013). Actually, it was my ECU relay (109). Today, I tried to hook up thin wires to my 180, but there are 7 blades, and I found it very difficult to keep them from falling off or touching each other. Consequently, I can't say I got accurate results, but I think I found the following:

30 - constant 12v (key on or off)
86 - when I turn the key, it flashes on, then stays off for a few seconds, then has 12v
ST - When I first connected a test light to this, lit it up for a second, then went off, and then there was a whine/buzz coming from inside the dash somewhere. However, there is no whining/buzzing when I don't put a test light on it. At some point, when I checked the voltage on this, it was about 10.8 and at some point, it failed to light the test light, though I think the ground was still good.
D1 - With the key on, this shows .5 volts.
31 - At first, this turned on 12v with the key, and that disappeared when the relay clicked off.
G1/2 - Ground
G3/4 - Ground

I'm giving up before I break something. Maybe tomorrow I will feel differently.

To review:
I have no GP light when it's cold (no half second flash, no sustained light when the plugs are on). I have a CEL (00626, GP Indicator light, wire). New 109, relatively new 180 (June), new GP harness, four new GP's, relatively new and working 50A fuse. I do hear the relay click on and off. I have power to the harness, resistance is good on each GP, and the GPs seem to be working because when I wait for the relay to click off before cranking, it starts right up. There is no voltage going to the wire in the instrument cluster harness. When I do apply 12v to the pin (#20) at the harness connector, I do get a GP light, so the cluster circuit is working. The problems seems to be just the wiring from the fuse panel to the cluster, but I don't see how a person would be able to trace that wire, which is supposed to be white/green but is actually just one of 15 white wires going between the fuse panel and the cluster. I'd be content to string a new wire in its place if that would make the CEL go away, but I don't know how to get to it.

Thanks.

I don't meant to steal the attention from you mikerancourt, but I thought I'd just add my similar problem while there's a panel of experts looking at this thread.

I believe I have also not had the GP light come on starting it cold in the morning for a few months now. It's been starting up completely fine, but as I've gotten used to it starting fine and not seeing the GP light I started it a bit too quickly accidentally this morning and there was a noticeable pause/hesitation in the engine turning over before it actually did (was a bit rough) and now I've got a flashing GP light and a engine malfunction light (solid) whenever I start driving (they stay on the whole time).

It's not the brake lights (one of the potential problems I read) and the engine is starting up cold fine still, is it likely an actual GP fault (as I've never had a problem cold starting and still don't) or just a one time error on my part (starting the car without waiting a few seconds)?? I really don't want to buy a VAG com tool if I don't need to (tight on cash) and I'd like to have a good estimate of the problem before I go to a mechanic to get him to check the error codes.

Thanks for any help!

I looked up a Bosch 0281003013 glow plug relay and see it has 7 terminals. That changes what I said about the ECU monitoring the coolant temp sensors and controlling the glow plug light. With 7 terminals, they are controlled by the glow plug relay. I am surprised a 98 Jetta with a ECU has a 7 terminal glow plug relay (my 96 Passat has 4 terminals). What engine code is your Jetta?

At this point I suspect the problem could be:

1. the coolant temp sensor is out of spec,

or

2. the glow plug relay is bad,

or

3. some wiring in between those parts is funky.

or

4. combination of any of the above

Ok, so today the speedometer, odometer, and clock don't work (speedometer doesn't zero out, and it sort of ticks up until it reaches 140, the clock and odo are blank). I'm assuming this will tell folks something about my other problems. I'm assuming I will soon be buying a new cluster or getting this one fixed.
What do you think?

Do you know where the ground wire hits the cluster? If you do, I'd try to see, with your ohm meter, if the ground is good. If it has a good ground, I'd tend to suspect the cluster.

rdkern said:

Do you know where the ground wire hits the cluster? If you do, I'd try to see, with your ohm meter, if the ground is good. If it has a good ground, I'd tend to suspect the cluster.

Click to expand...

To really do this, I would check the ground vs. battery ground, negative post. You'll probably need some long test leads. Let me know and I can provide more details as to how to check the grounds.

Tony

I could use some more information about how to do this. Would it suffice just to touch a lead to a ground on the cluster, not the actual wire going into it? I have some access to grounds where bulbs go into the cluster?
Can I just use a long piece of wire i have laying around to "make" an extra long lead or would I have to worry about gauge?
Thanks a lot. This is getting interesting because I am not on the road, going from upstate NY to San Diego. Sheesh.

What electrical tools do you have?

Meter/DMM? Test leads? Extra wire to make a long test lead?

Tony

I have a cheep multimeter (does ohms) and some wire (12 gauge I think). I also have test lights.
I found the ground wire in the harness connector, and it does work. If the clock wire is tbd one I think it is (not the one Haynes says), that does give me 12v.

Ok...

If you are unsure about any steps, or this is beyond your capability, DO NOT ATTEMPT! I cannot be held responsible for your actions!

1) Strip both ends of a wire that will reach from the battery to where you have the ground at the cluster, that you are trying to check.

2) Cover one end of the wire with electrical tape...this is a safety thing!

3) Connect the other end to the battery NEGATIVE terminal AT the battery.

4) In the cabin (of the car), remove the electrical tape from the wire and connect the wire to the negative of the meter.

5) With the meter on Ohms, touch the wire to the ground at the instrument cluster. The meter should read near 0 ohms. As a matter of fact, it may read 1-2 ohms. Certainly less than 10. If you read >100, disconnect that ground and clean it.
5A) After cleaning, recheck the continuity of that ground. It should now be <1ohm.

6) If the resistance looks good (<2ohm), continue on, BUT BE CAREFUL.

7) If possible, and no potential exists for damage to the car or injury to yourself, turn on the ignition with the instrument cluster plugged in to the harness, but loose.

8) Switch the meter to DC mV range.

9) Touch the positive meter lead to the ground point. You should read <1V, and prefereably <100mV difference in ground potential. If you are reading >1V, I would clean ALL the grounds you can find: 2 near the battery, the main engine ground, the small grounds near the cylinder head, and any ground you can find behind/near the cluster.

10) If all these checks are good, its time to start checking elsewhere.

Post back if you have any questions or any results you get.

Tony