Glow Plugs 101

It seems that a very common DTC is the one for the glow plugs (P0380 or 16764). It is a simple procedure to test & diagnose this code & I hope that this quick tutorial can save some of you from an unecessary visit to your dealer. I appologize in advance for the poor quality of the pictures, but even bad pictures can say a 1000 words!

The tools you will need are as follows:

Digital multimeter ($10-20 from most auto parts stores)
10mm socket to remove engine cover
10mm deep socket if plug replacement is necessary

First step is obviously to remove the engine cover and find the glow plug harness.

Remove the harness by pulling on each plug. It pops off like a spark plug wire. With each plug exposed, you can begin testing each one. Set the dial on the multimeter as low as it will go (most only go down to 200) As you can see with my cheap multimeter, it shows a resistance of .5 ohms just from the plating on the leads.
Find a suitable ground for one lead & place the other lead on the tip of the glow plug. Test each one & record the readings. In my case, I had to subtract .5 from the reading to get the actual value of the plug. 3 of the plugs showed a resistance of .8 ohms and one .7 ohms which is within allowable limits.
If you find that you have one or more plugs with either high resistance, no resistance, or a large variation between the 4 plugs, then you have likely diagnosed the problem and the plugs need to be replaced. If they are all the same or within .1 or .2 ohms, then the plugs are not the problem.

If you find a bad one or two, there is a debate on whether to change just the bad ones or all four. Depending on the mileage on your car, it is acceptable to change just the bad one/s. Make sure you test it to see if the resistance is close to the rest otherwise, you will continue to get the CEL. If you have high mileage, you might as well replace them all as you have gotten use out of them and will probably have to perform this procedure again in the near future.

Replacing the plugs is the same as replacing a spark plug. Just spin it out & replace. Make sure not to cross thread the new plugs though. The torque specs for the plugs is 11 ft/lbs. If you don't have a torque wrench, then just snug them in. The thread is very fine and the aluminum can easily strip. After the plugs are in, reattach the harness (make sure each one snaps into place) and then get the code cleared (it will not clear by itself). You can go to your local Autozone or contact a member in your area with a VAG-COM.

If you tested the plugs and all checked out ok, then your code was likely thrown by a bad harness. Why would a harness cause a code? Check out This thread . The monitoring system is very sensitive to resistance variations and that small amount of corrosion caused enough resistance to illuminate my CEL 4 times, each within a few hundred km's after having it cleared. Since I changed the harness, no CEL for 30,000km now.

Some people have been successful with cleaning the tips of their glow plugs and putting an anti oxidant paste in the harness. However, as you can see from the pics in that thread, the surface that was corroded was inbetween the two pieces and can not be cleaned. You could try this approach and it may work for you. It will save you from having to replace the harness and might last indefinately. Check out this thread for some products to use to clean your harness. At the very least, pick up this product to prevent the harness from going bad to begin with. An ounce of prevention.......you know the rest.

If cleaning the harness didn't work for you and you do decide to replace your harness, here is how I did it:

Tools required:

Wire stripping pliers/crimping tool
Butt connectors
Heat shrink tubing
Heat gun or lighter

I started by cutting the wires on the old harness. Cut as close to the flex guard as possible so you have lots of wire to work with. Then cut off the connectors that come on the new harness.
Wiggle the old harness out and the new harness in. Strip a 1/4" of insulation from the end of each of the four ends & crimp on the butt connectors. Don't forget to put the heat shrink tubing on before you crimp.

Use a heat gun or lighter to shrink the tubing to provide a waterproof seal over the conection.

Snap the harness back onto the plugs and put everything back together. As stated above, get the code cleared and you shouldn't have any more CEL issues related to the glow plug system.

If you do need to replace any glow plugs, they are available at many online places for 1/2-1/3 of the price the dealer charges. I have also seen them on E-bay for very cheap, just do a search for 'tdi glow plug'

Disclaimer: This writeup is for information purposes only and is intended to help anyone who feels comfortable around engines. I cannot guarantee that it will fix ALL occurences of a CEL. I hope it will help most of you and at the very least, save you from an expensive visit to the dealer. Good luck.

Well said and done. Just finished most of this job myself - with a local VAG-com guru resetting the CEL a week or so ago (thanks again, Mark). Only thing I would add is to suggest the deep socket 10mm be a "thin wall" if one can be found (there isn't much room between the GPlug and the engine block). Otherwise you may want to get a cheep-o and grind it down a touch.

Glow Plugs 101 *DELETED*

Post deleted by wingnut

Quick, before I place an E Bay bid and make an a$$ of myself. Will the A4 glow plugs work in an A3?

Back to the top for the newbies.
Seems like a popular topic this week.

Wingnut,

Thanks so much for that detailed description. I have been pulling the P0380 and when I clear it, it stays clear for about a week or two and then it pops back up. You just save me over $100 with that detailed explanation. Thanks,

Alex

Wingnut,
Let me also express my gratitude for your detailed post on replacing the glow plug harness. I recently bought a 2000 Jetta with the CEL on, the owner thought the culprit was the MAF which he had just recently replaced. Vag-Com indicated the fault was 16764, I replaced the glow plug harness, cleared the CEL and have not had a problem since. thanks again.

great pictures and good write up.

Good job Wingnut. You can buy at Autozone maybe other stores Heat shrink butt connectors which work great and save a step in changing the harness. you won't need to buy heat shrink and connectors buy it all in one. IF you are going to buy heat shrink try to find a electronic store that carries the 4 foot long tubing of differant sizes, I have found that radio shack tubing is very poor compared to the good stuff. you can tell the differance by feel, good shrink is soft the radioshack stuff it hard and does not shrink as good. A 4 foot piece ot tubing at a good shop will only run about 4 $ and i would but several sizes it will come in handy for other work on the car. It also will shink about 50 percent so keep that in mind when buying.

Thanks guys. Although I must admit that all I did was post stuff that I learned from others on this great forum and put it in one place. Once I get a good digi cam, I'll do a better, more comprehensive 'how to'.

As for the heat shrink tubing, I used seperate butt connectors & tubing because the combo ones that I have found are poor quality. I find the heat shrink tubing too short to seal properly on the ends to make it completely waterproof & the metal connectors are a cheap alloy that are not very strong. The heat shrink tubing I used came from a tractor trailer repair shop and has a glue lining inside. It is designed to be used in external applications that have to resist hundreds of thousands of miles of heat, salt, rain, snow and any other kind of conditions that these trucks go through. Once heated, it shrinks plenty small enough and the glue melts & seals the ends very well. It even hardens to make a solid connection with no flex.

Thats why you buy Shrink tubing in 4 foot sections. The stuff you use was first IIRC by the Telephone CO. for sealing underground connections and is THE BEST way but you can still use good shrink tubing just don,t by the cheap stuff. I have worked with it for 30 years and you can tell the good stuff from the bad. Cut to FIT is the bestway to go. All the clusters i have installed also have shrink on the solder joints. I don't like Black electrial Tape. Still the best right up on this install and should be posted at the Top of 101 or on the FAQs

Yes excellent post. I just got my first CEL in 100Kmi (exactly) the other day. checked plugs, replaced harness. problem solved. Just wanted to mention that I removed the big vaccum pod/resivoir. made access easier. Thanks wingnut (even though I didn't see this thread untill after I did my harness.

Its glow plug season again.

Back to the top for the newbies

That's funny... you folks up there have been below 32 at night for some time.. it's coming our way pretty fast...
Nice thead, should be a DIY /images/graemlins/grin.gif

Can anything be learned from the appearance of the GPs? If one of the four appears lighter or darker, can you "read" them like spark plugs?

The bad GP that i removed had obvious signs of wear, the bottom of the GP was burnt, like it had worked overtime.
You can look at the new plug and compare the 2 to see the difference. The used plug will also be shorter most likely.

Hmmm... I had three completely coated with carbon, and one with just a ring of carbon toward the end.

Thanks Wingnut...I still have to confirm that my CEL is this problem but it really feels like it's the way to go. Your timing couldn't be any better. /images/graemlins/laugh.gif

Ok ... parts question ...

The plugs I removed were VW part number 0 100 226 227 (not avail from IMPEX)

The plugs I installed were VW part number 0 250 202 022 ($27.15 from IMPEX)

IMPEX lists VW part number N10140105 (10X1X25) for my car ($20 at IMPEX)

Which is the right glow plug for my 99.5 TDI? /images/graemlins/confused.gif

And what is the difference between all these part numbers? /images/graemlins/confused.gif /images/graemlins/confused.gif

Ive been getting that code for a while now. Will it hurt anything if I just ignore it? I live in Louisiana and it never gets below 20 F. I haven't had a problem starting my engine, so far the coolest its been is mid 40's. How cold does it have to get before I will have problems starting?

I pulled my cluster and put a piece of tape over the CEL over 3 years ago because i got tired of looking at the light. Most likely like mine your harness is bad. When i finally changed the harness i have not had a priblem since. But still have the tape over the CEL. Got along fine without check engine lights for the first 30 years of driving don,t think i need one now. But i do use the Vag-com to check for codes every few months.

Hot topic again this week.

Back to the top!!!

Can this thing get a sticky to the top? Moderators?

It is hot alright... i got a cel last night.. i'm hoping it is only a plug...
I agree with you wingnut this should be a sticky up top /images/graemlins/grin.gif

Another way to check the glow plugs is to remove them and put a negative wire on the body of the plug and to negative side of battery and positive on top of the plug and positive side of the battery. You can then see if it gets red hot. You can do this if you don't have a tester or if your tester is junk (like mine). Be careful not to burn yourself.

Unfotunately this test isn't good enough for the TDI. The ECU throws a code if the resistance is out of spec... so the GP may still heat just fine, but if the resistance is a little too high or too different than the other three it will throw a code. So... checking the resistances is really the only way to see if the GPs themselves are the source of a CEL.

thanks wingnut, I'll see if this is the problem. meanwhile, does anyone know the torque specs for the GP's?

11 ft/lbs...

When i replaced the this last bad gp i did plug all of them in to see them get red hot and, they all did light up pretty quick.. the bad one did not.. i have also seen that the bad ones take a while to get hot if they even do..
I also suggest the resistance test first... /images/graemlins/grin.gif

Since the search function is temporarily down, I thought I would bump this puppy back to the top! I am getting a new camera any day now, so once I get a spare day, I will go through the procedure again, take better shots & do a more comprehensive 'how to'. Maybe then it can get a sticky?

If not we'll just bump this thread up for newbies or other folks who need a good guide /images/graemlins/grin.gif