Glow plugs 101 ***Ver. 2.0***

dfdtruckie said:

I have a 02' auto Jetta and read I do not have coolant temp sensor.

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Wrong...

What was the code that was read before it was cleared ??? It would be nice to know...

Yes, Vag-Com can give a more detailed explanation than a generic OBD tool... check the Vag-Com list to see if there's someone nearby...

Yuri.

I don't remember the code number, when we checked it, it listed the #2 plug as low temp. After that I purchased 4 new plugs and replaced all of them.

dfdtruckie said:

... After that I purchased 4 new plugs and replaced all of them.

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Are you saying that you started the engine after you cleared the code and before you put in the new glow plugs ??? If so, you will have set a new code, and will need to clear that one...

Y.

Replaced the plugs, then ran the car and had the code cleared. Then it came back on.

Yuri, your right, the PD's do use a lower voltage on the GP (arround 7v dropping to under 5 after the initial heat up)

What's the story on PD GP's resistance? My CEL lamp came back so I checked the GP's but the reading was odd on all 4. What sort of Ohm reading should you get on a PD GP?

I still have not been able to contact Brian to order a Vag Com (not responding to my Emails), so I can't clear my codes yet.

Martin

brucep said:

How do you know GPs are not operating?... If you actually READ my past appends... the GPs ARE powered for several minutes AFTER starting the engine. This is when the ECU does its current-sensing and may throw a code.

If you have any knowledge of electronics... the ONLY way to detect current is to measure voltage across a known resistance. (There is no such thing as measuring current .... only measuring voltage and then applying Ohms law.)

Further, to measure the relatively large current that the GPs draw, the resistance has to be very low. . Ideally, the resistor for measuring the current should be less than 1/10 of the resistance of the glowplugs.
(Otherwise, the voltage-drop would be too much)

If the GPs are 1.0 ohms... this means the resistor may be 0.1 ohms (or less) Even with these paramators, that would make the operating voltage at the GP almost as low as 11.5V (theretecally)

Also, you must account for the fact that the GPs are resistive heating elements. This means that their resistance GOES UP as the GPs get hotter. (if 1.0 Ohm cold.... may be as high as 100 Ohms hot)

I hope this answers your question. (I really dont want to get much deeper into electronics theory here

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BruceP

I read this thread and searched for others and have not yet seen a clear explaination of how the ECU senses a fault.

It was my understanding that the glowplugs did not come on at all unless the coolant temp was below a certain level.

Can you point me to (or provide) a clear explaination of how the ECU detects a glowplug fault?

Best

Darren

Here's my tale. Last spring the dash indicator light came on, but hey it was getting warm and it started fine. So I ran all summer (15,000 miles +/-) with the dash indicator on. About October I installed new plugs and could see that plug number 3 was all covered with carbon. Well it still stated good all winter so far, but the light was still on. Note: the glow plug light doesn't stay on long and hasn't since I had this symptom. But I went for inspection Friday and it failed. This weekend I installed a new harness ('03 Jetta) and ran it 125 miles since. But I still have the light. It takes about 35 sec to come on. I stopped at Auto Zone and Advanced and they both read the same P0673 which is #3. They wouldn't clear and both said it should help itself. What do you think? I need help to get it re-tagged.

The glow plug code on the ALH motor will not clear itself. It needs to be reset by a scan tool or Vag-com.

what does &amp mean?
I know I'm going to feel foolish for asking but go ahead and tell me anyway.
Thanks

GNTDI said:

what does &amp mean? I know I'm going to feel foolish for asking

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Not a silly question at all !!!

It's simply something that got left over in the message threads when the forum software was converted from an older system... the ampersand character is confused with a quotation marker or a link... short of manually cleaning out the message threads, there's no easy solution, so we just "suffer" in silence...

All the best,

Yuri.

My MIL light is on

I started doing research on why my MIL light went on yesterday. From my readings I assume it has something to do with the glowplug system. I do not have a vag-com so I went to harborfreight and bought a generic ob2 reader. When I put it on the car (03 NB) it did not indicate any codes. It did light up and say "launch" which it was supposed to say according to the instruction book. Anyway, its back in the package and will be returned. I plan to buy one based upon recommendations of forum members. I looked on ebay and found 2 basic types. Type one is a cable and some software for your laptop. Type 2 is and individual unit like the one I bought from harbor freight. Both types are available that specifically say they are for VW/audi. Any recommendations?
I plan to put an ohm meter across the GPs tomorrow and see if I can find anything. I suppose I'll check the relay next and then try the harness. Should I do this stuff before I get a good vag-com code or just go ahead anyway. If I do have a bad plug, is it safe to drive on or should it be replaced asap?

Any advice would be appreciated.

You can safely drive without any of the glow plugs functioning...

That said, you should find out what the exact code is... Please update your profile to indicate your location... there may be a Vag-Com owner living close by... (check the Vag-Com list at the top of the page, also...)

There's no comparison between the results you'll get from a Vag-Com scan and what you'll get from a generic reader... so try to find someone who has one and get the real story... I'd say you should save your pennies and get a real Ross-Tech Vag-Com if you can manage it... the generic cables you'll find on eBay generally will work only with the older versions of the software (still useful, though...)

If you're in the U.S., most AutoZones and/or PepBoyz will scan the car for free... at least we'll have some idea of what the problem may be...

All the best,

Yuri.

Will I put and ohm meter across the plugs. I had the meter on the 20 ohm scale and 3 of the plugs measured 0.0 ohms. One plug measured 0.29 ohms. Is this enough difference to say that this one plug is bad?"

I just tried to test the relay but with my fat hands I couldn't get at it. I did remove the air hose which gave me some more room but I still couldn't get at it. I did feel the wires going into it but was afraid that I would break something if I continued. From what I read at the beginning of this post, you have to pull this relay to test the harness. Why cant you just put a volt meter across each plug on the harness while the glow plug light on the dash is on? I know its only on about 4 seconds in the the northeast right now but if my wife was turning the ignition key and I was looking at the volt meter, wouldn't this have the same affect?
I did put the volt meter across the fuses on top of the battery and all were fine.
Should I assume it's the harness and try some of that spray that was mentioned? Is there a spray that is good that is available at my local autoparts stores, pep boys, strauss auto, autozone? The harness from the outside looks very clean. My 03 NB has 34k on it but I do live very close to the ocean.
I will be contacting a club member who lives near me that has a vag-com so hopefully this weekend I can pull a real code.

Thanks for the help,
Gregg

Novice Questions

Wingnut: Great Writeup. Threw CEL today, have questions before I start:

1. I'm confused whether the temperature has to be below the (approx) 48 degree mark to throw a CEL (so the glow plugs HAVE to be used to start the car). Or if a CEL can be thrown even if the glow plug light stays on just for a second or two during its normal check, like when it's warm outside.

My car is usually in a garage, and I am not sure if it's cold enuf to have to use the glow plugs. So, in order to see if any fixes work (spray the harness for example) do I have to keep the car outside to be sure it's cold enough for the glow plugs to have to be used? Sorry to be so wordy. In other words (ack!) if I had a real problem, the CEL may never come on, if the weather is too warm? And I sort of want to force an error (in the cold) so I know the problem is fixed, so when I drive in colder climate (vacation?) the car will start okay.

2. When reinstalling glow plugs what should I spray them with? You mentioned anti-sezing agent. What is that?

3. You mentioned using a 1/4 socket instead of a 3/8 to get around injector wires (?). The 1/4 socket is "more skinny", is that why use it?

4. DEEP Socket? Really dumb question here. How do I know if I have a deep socket? And, you need it so the "nub" on the extension doesn't hit the top of the glow plug?

5. Someone else mentioned when removing the old glow plugs to turn counter-clockwise two times, then clockwise once, then two counter, one once, and so on till plug comes out. This was to prevent striping the hole. What do you think?

6. Finally, should I spray the tip of the plugs (old ones, before measuring) with the Dexoxit to clean them to get a more accurate ohm reading.

Thanks!

I realize that you were directing the questions to Wingnut... but I beleive I can provide the answers to most of them. I am sure Wingnut can fill in where needed.

1) In my experience, the CEL can come on several minutes AFTER starting the engine. I do beleive the ambient temp does have to be low enough to enable the afterglow. In my experinece, it is the afterglow function that can detect a problem and throw the CEL.

2) Antiseze is not a "spray", it is a silver-colored goopy paste. You can get a small tube of it that can last a long time because you only use the slightest amount to coat the threads before final assembly. I usually run the GPs down/up several times to spread the antiseze evenly before final snugging. (Only snug less than 1/8 turn after it hits the "seat")

3) Using a 1/4" DRIVE extender with 10mm DEEP socket is perfect tool for dealing with the glowplugs. I also use a 1/4" driver (looks like screwdriver handle) to do most of the work... I only use ratchit for initial loosening/snugging.

4) A DEEP socket is a socket that is LLOONNGG (about 3x longer than a standard socket) It is called "deep" because the top of the glowplug can stick up inside the socket without interfering with the operation of the socket.

5) I am the one that mentiond using care when removing GPs that have been installed for many years. If you re-read my append, it says to spray somthing on the threads each time before screwing back in....this helps to get some lube down in there as you work the GP out of the hole. The main thing here is to be cognazant of how much torque you are applying to unscrew.... if it is taking too much torque STOP before somthing bad happens.

6) There is no need to "spray" with deoxit. Deoxit is VERY expensive and it is a waste to just spray it all over. It is much better to spray small amount on kleenex or papertowel and WIPE the exposed connections on the GPs. Dont be afraid to sqeeze hard as you wipe to get the crud off. Keep wiping with fresh surface of kleenex until it no longer removes any crud.
While you are at it, pull the connectors from the COOLANT HEATERS and wipe them clean using the same tecnique.

PS: Use the Deoxit "spray" to get down inside the GP harness connectors. I also used a Q-tip to then wipe the insides of each harness connector.

If you are using the Deoxit "kit" from RadioShack that has 2 bottles in it. One of the bottles is a CLEANER and the other is the PROTECTANT. If you read thru the Deoxit website, they explain that the PROTECTANT does not contain very much solvent and is not good for doing the cleaning.

brucep said:

Antiseze... is a silver-colored goopy paste.

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Although not absolutely necessary, I use high-temperature anti-seize on the glow plug threads... it's copper-colored...

Other than that tiny bit, good explanations !!!

All the best,

Yuri.

Hi,
I was wondering if someone could take a look at my last post and give me some advice.

Thank you

Brucep: thanks! for your detailed response. as soon as I find the Deoxit (none in my Radio Shack) I'm going to clean harness, check plugs, etc. Of course, if problem stays very intermittent, I may wait till weather warms up .

Thanks for the feedback on my resetting and that was exactly what it was. However I found that when I called around Nashville several wanted $100 to reset it and the VW dealer is way out of my way. Instead I kept calling and found one that said he'd do it, but it must be something else. When I got there I asked how much and he said that it it cleared it was free and if it needed repair I'd have him do it. Fair with me. It cleared and he wouldn't take a dime. It's nice to find an honest repair shop. If I need repairs on either of our VW Jetta TDI's he'll be the first on the list. So if in Nashville, try Import Tech at 222 Feslers lane.

DieselCruiser said:

When I got there I asked how much and he said that it it cleared it was free and if it needed repair I'd have him do it. Fair with me. It cleared and he wouldn't take a dime. It's nice to find an honest repair shop.

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That is the kind of mechanic that you can TRUST when you need some work done on your car.

Anyone that charges $100 just to clear the codes is a crook!!

Thanks for the info on glow plugs. I had a glow plug circiut malfunction code and the dealer said it is usually the harness. They said $180.00 to diagnose it and about $250.00 if it was the harness. Scary. I followed your steps and found I had a bad glow plug. I replaced it and reset the code. All fixed. Thanks again.
tom

I did not read this entire post so someone has probably already said these three tips. 1. Always change glow plugs when engine is cold. 2. Always keep a 10mmX1.00 tap in your tool box to clean threads just in case, and on 02 and 03 the ecm may set a code for #2 and the one in question is # 3 or vise versa.

OK, I'm trying to follow the awesome advice on this topic. I have a couple of questions.
#1. Is it really necessary to disconnect the coolant temp sensor? I set up my voltmeter so I could read it from the drivers seat and cycled the ignition switch a few times.
#2. My plugs checked out fine, .9 ohms on all of them. My fuses checked out fine as well. Checking the relay the way I've described in question #1, I got 6.98 volts at each plug location. I have an '04. Is 7 volts correct on this year model or should it have been 12?

Thanks for the help.

DarrellM5 said:

I have an '04. Is 7 volts correct on this year model or should it have been 12?

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Yes, the PD engines use ceramic glow plugs running at about 7 volts...

Yuri.

A3 jetta

i know absolutely nothing about electric but i wanted to check my plugs. This is a code i had thrown a few weeks ago.

01050 - Glow Plug Monitoring
35-10 - - - Intermittent

After i got my settings right i checked the plugs and got from 0.6-0.8 readings for all 4. But i am lost about how to check the harness. I tried a few different times to get a reading and came up 0.0. When i put the key into the glow position the light on the dash goes off before i can even get my hand away, after i do it a few times. Also when you stick the lead into the harness what exactly are you trying to contact or is just having it in there enough?

When i start my car after sitting all night its real cold in ny right now, but even when it was in the mid 30's, the glow light comes on and stays on for a good 20-30 seconds, what might cause that? I thought it could be my dying battery but now its exactly the same with a fresh battery.

A semi related question, are the black return/ vacuum looking hoses that go from injector to injector just regular vacuum line or is that some special high temp/ high pressure line? Can you use high temp silicone line on it? I'm asking because i touched one and it was brittle and the cloth on the outside ripped.

Vinyl Addict, I think that what you're seeing from the GP light indicator on the instrument
panel is probably normal ... the system needs to pre-glow, when you first start the engine,
it is going to first heat up the combustion area in the cylinders, and I believe that
takes at least several seconds when the engine has become quite cold. The light on the
panel is surely telling you that the engine is performing that step.

When trying to measure the electrical continuity of the GP harness, the connectors in those
GP boots are like a sheath of spring contacts, i.e. a socket, i.e. a female sort of fitting ...
so if you can either get a section of clean, thick, single-conductor bare copper wire (sorry
I don't know the gauge), or something that matches a used glow plug of this type, it would
fit perfectly as a probe end. Actually the probes that come with a typical multimeter (i.e.
a Volt/Ohm meter) usually contact the connector well enough, if you hold it in there with
your hand and keep some pressure toward the side of the rubber boot, so that you get
metal-to-metal contact.

About those little rubber hoses that connect between the fuel injectors, they carry "return"
i.e. excess fuel back toward the fuel filter. I don't think that the pressure in them is
particularly high ... the metal fuel lines supplying the injectors carry high pressure. I
think they are regular (diesel #2) fuel line material, nothing fancy but I don't know whether
you can use that alternate material. Good luck; Larry.

VA, also concerning that "intermittent" fault code, it most likely involves the
electrical connection between the GP harness ends and the terminal ends of
the glow plugs ... i.e. the problem is usually not in the GP harness, but rather
a bit of shaky connection where those spring contacts squeeze the GP terminals.
I imagine in cold temperature regions, it must be a bit worse than in warm,
dry regions. So, you have to either keep cleaning the contacts inside those
rubber boots, or else eventually buy a replacement harness. Some folks in
this thread have tried more approaches such as squeezing the connectors to
tighten them, inserting metal foil, etc.

so far its been single digits this week when i start the car and as long as i let the gp light go off and wait for the click of the glow plugs to cycle off, i haven't thrown a code. I guess i'll get some of the products mentioned here and try to make the contact better between the harness and plugs.

THANK YOU THANK YOU THANK YOU!!

I had a quote from the dealer for $700 bucks to replace my glowplugs and harness....maybe I'll get lucky and fix it myself...thanks again!!