Glow plugs 101 Ver. 2.0

leegravel · Jun 13, 2015

I checked the plugs again; they all read 0.7 ohms. I'm gonna try some deoxit D5 and try to get someone to clear the code for me. That seems to be a mission in itself. Thank you for your help.

leegravel · Jul 3, 2015

Glow plug type?

I'm a bit confused on which glow plug I need to replace the old one with. I read a forum about the old style ceramic plugs breaking apart in the cylinder, and a "reflashing" needing to be done with the new steel style GP's. Is this something i need to worry about with my 05' TDI?

02TDIjettaowner · Jul 12, 2015

2002 Jetta TDI Glow Plug Relay

I am having trouble locating the Glow Plug Relay on my 2002 VW Jetta TDI. Some say it is under the steering wheel console on the relay panel in position # 10. Position # 10 is empty with no wires to even plug in a relay. Some say it is under the windshield wiper arm on the driver side. I see a Bosch relay (0 281 003 023) under the windshield wiper arm but can not find it anywhere to see if this is indeed the Glow Plug Relay. HELP!!!

dandtpaul · Jul 13, 2015

2006 Jetta GP harness

Started throwing a CEL this week. Autozone said it was the #3 GP. Started to trouble shot this evening. As I pulled the harness I noticed the #3 boot is cracked half way around. Looks like I need a new harness. On mine it looks like the end going into the wires is molded on the wires. Do I just strip back enough of the tubing / insulation to get to a point I can slice the new one in?

corpsman5 · Sep 3, 2015

I realize this is an old thread, but thanks for posting. great info, very detailed and very thorough.

sav · Sep 11, 2015

2011 Glow plug removal

New to the forum, and this is my first diesel.
CEL is on and codes all point to the #1 glowplug.
Followed a guide to getting access to the plugs, but once I've loosened everything to give the harness enough play to remove the plugs, I'm not able to actually pull them out.
Not sure if I'm missing something to disengage a clip on them or if there is something wrong that is preventing them from coming loose with the amount of force I am applying (which I think is considerable given that I haven't seen anyone else with a similar issue).
Any help would be appreciated from anyone that has removed them to test them.
Thanks.

DieselCecil · Sep 19, 2015

What?

If anyone who called himself a "mechanic" used but connectors to install my new glow plug harness (or ANYTHING on a car) I'd kick him in the crotch, refuse to pay him and tell him to buy a soldering gun.

Using those crappy terminals is NOT the way to work on your car. That's why they invented soldering guns, solder and heat-shrink tubing.

If it's worth doing it's worth doing the right way.

DieselCecil · Sep 19, 2015

brucep said:
This is a good write-up and plan on getting some contact goop for my glowplug-harness connectors soon.

Being trained in electronics and military soldering, I feel compelled to make some comments. Keep in mind that I have been troubleshooting million-dollar computers for many years and have been known to isolate/resolve automotive electrical issues that had other folks stumped. I know 100s of ways to take voltage measurements to isolate a problem in a live circuit.

The crimp-on connections are used by jobbers because it is quick, It is NEVER better than soldering. Taking the time to solder all connecitons makes a huge difference in reliability.

Using CRIMP-ON connecitons at any point under the hood is asking for trouble. I realize that portion of your write-up is from your original harness replacement but instead of having essentually 4 crimp-on connecitons (2 butt crimps per connection) i suggest that a standard twist-together and solder would be infinetly more reliable. This is especially true under high-current conditions where even a small resistance can become a large voltage drop (ohms law)

This URL explains wire-connections and soldering.
http://www.teamrocs.com/technical/pages/connections.htm

You also mislead folks by suggesting that there is no way to "test the harness". I can think of at least 5 ways to test the harness.

Here is one way.
You can measure the voltage drop ACROSS the harness using your DVM (DigitalVoltMeter) by putting probes at both ends of the glowplug harness. (use a length of 22guage wire wrapped around glowplug to connect probe) This measurement will tell you how much voltage is LOST in the cable (due to intrinsic resistance) and not getting to the glowplugs. Again, ohms law tells us that the glowplugs must be drawing the expected current for this test to work.

Another way to "test the harness" is this;
Place DVM probes between solid ground and the glow-plug end one at a time to check the voltage at each glowplug. Any reading significantly less than battery voltage indicates there is resistance in the harness. (again use a length of 22guage wire wrapped around glowplug to connect probe)

The "secret" with testing the harness is to have the FULL CURRENT FLOWING thru it when testing. Otherwise, a 'whimpy' harness may not exibit a problem. Just checking the voltage at an unplugged harness end tells you very little about the condition of the harness. (Look up the input resistance of your DVM and compare that to harness resistance to see what I mean)

The "contact goop" is called dielectric grease.

Judson · Sep 19, 2015

Everything replaced - still have the code!

Folks -

Need some help!

I have replaced the glow plugs, glow plug harness, used a glow plug harness connector kit (from idparts), and replaced the glow plug relay.
I was careful with the wire connections. They're good.

I figured she's 14 years old, so...no harm done. And winter is coming. She starts fine, better than ever, though I haven't had the chance to let her sit overnight yet.

BUT I still have this fault code. Each time I clear it it comes back. Argh!

16764 Glow Plug/Heater (Q6) Circuit
P0380 – 35-10 – Malfunction - Intermittent

Searches on this forum say that it's one of the glow plugs, or the harness. Except now they're both new now.

Anybody have any ideas?

Thanks!

Jud

ymz · Sep 19, 2015

Did you clear the error code with a scanner (VCDS or generic) ?? It won't go off by itself...

Yuri

turbocharged798 · Sep 19, 2015

DieselCecil said:
If anyone who called himself a "mechanic" used but connectors to install my new glow plug harness (or ANYTHING on a car) I'd kick him in the crotch, refuse to pay him and tell him to buy a soldering gun.

Using those crappy terminals is NOT the way to work on your car. That's why they invented soldering guns, solder and heat-shrink tubing.

If it's worth doing it's worth doing the right way.

You do realize every connector in the car is a crimp connector right?

Solder is for PC boards.

Judson · Sep 20, 2015

I got the code details from VCDS, so yes of course I cleared it. Multiple times!

Thanks,

Jud

Strykeviper · Sep 20, 2015

Use a multimeter to ohm test the glowplugs one at a time. They should all be about the same reading. Even if they are new, you could have the random faulty one that made it past QC. I had the same issue with a recently replaced harness and it ended up being a single GP. Replaced it and cleared the code and no more MIL.

kamaksi · Sep 28, 2015

Glow plug frustration

Ok so here it goes and i am sure everyone has heard hundreds of variations so i apologize if i do not have time to scour through 110 pages of posts.
First i get the check engine light and i am 95% sure it was the glow circuit #3 fault code. It comes on about 10-15 seconds after startup.
1) checked glow plugs - all good
2) checked the wiring up the the wiring plug behind the air box - all good
3) replaced the Glow relay under the wipers with a new one - all good
4) checked the fuse on the batter - all good
5) the glow plug socket under the wipers all intact and not indications of hot spots. - all good
6) automatic transmission do no trans glow plugs
7) 2002 VW jetta TDI
I am at wits end trying to figure this out and have been hunting at this for about a month now and winter is approaching and dont want to be caught with out these one morning! Any thoughts any suggestions ... i am going bonkers here

John Wardigo
2002 VW jetta stage 2 rocket chip tune
bosio 357 injectors
VNT-17 turbo
Free flow cat and muffler with larger muffler
OMI intake

Vwscream · Sep 28, 2015

Have you checked the resistance on each plug when harness is removed? It will possibly point to failed plug in your case. Only things left are to check for proper 12v at the plug harness, amp draw on the wires and plug resistance. Take the DVOM and ground it to the cylinder head and test each plug on at a time.

Digital Corpus · Oct 7, 2015

Vince Waldon said:
For your purposes ignore the red wires in the above picture... that's my harness delete. I've threaded the tops of my glowplugs for 8/32 Kepps nuts and run individual spade lug terminals... another option for those so inclined

I've always wanted to do this, but I also couldn't stand putting US threads on a metric car. However, by fluke, I was browsing through a manufacturers catalogs and noted they sold glow plugs.

Though it's off by 1 mm for the length of the tip, and the body is 10mm shorter, I confirmed that the thread placement, pitch, and body length are all proper for the B4' and ALH's. One can thread their own plugs, or buy some shorter ones with M4 threads manufactured onto them. Anyhow they belong to the 1998/1999-2000 Land Rover Freelander. For barely over a 20, I might as well order a set...

Vwdianne · Oct 14, 2015

Is it ok to drive 1300 miles, when the engine light is on? The code is for a glow plug. The car (2003 tdi Jetta) is running and starting just fine, except for a slightly higher idle speed - 900 rpm's. Thanks.

Digital Corpus · Oct 15, 2015

The glow plugs only help start the engine. Won't helped hurt if you're in warm weather. Just replace them when you have a chance before the cold sets in.

rdkern · Oct 15, 2015

Vwdianne said:
Is it ok to drive 1300 miles, when the engine light is on? The code is for a glow plug. The car (2003 tdi Jetta) is running and starting just fine, except for a slightly higher idle speed - 900 rpm's. Thanks.

Idle speed should be 903. You can drive forever with a glow plug light on.

However, get your ohm meter and ohm the four out. They should all be less than 1 ohm and close together with respect to the readings. Any big deviation means you likely found the cause of the light.

If they all check out, it's likely a harness or connection issue.

Do you have vcds?

obie84 · Oct 15, 2015

Can't remove glow plugs on 2010+ TDI! Help!

sav said:
New to the forum, and this is my first diesel.
CEL is on and codes all point to the #1 glowplug.
Followed a guide to getting access to the plugs, but once I've loosened everything to give the harness enough play to remove the plugs, I'm not able to actually pull them out.
Not sure if I'm missing something to disengage a clip on them or if there is something wrong that is preventing them from coming loose with the amount of force I am applying (which I think is considerable given that I haven't seen anyone else with a similar issue).
Any help would be appreciated from anyone that has removed them to test them.
Thanks.

I'm having the same problem as the poster above, and hope that one or more of you experienced folks on the forum could help out us non-experts. The trouble we are having is simply removing the glow plug connectors and then the glow plugs without causing damage to any delicate bits of the plug or harness. The plastic connector is very resistant to careful pulling.

Our question applies to 2009 and later diesels which have different type connectors & plugs than earlier Jettas, so please no answers about earlier models.

Please help us out!!!

Digital Corpus · Oct 15, 2015

rdkern said:
Idle speed should be 903. You can drive forever with a glow plug light on.
However, get your ohm meter and ohm the four out. They should all be less than 1 ohm and close together with respect to the readings. Any big deviation means you likely found the cause of the light.
If they all check out, it's likely a harness or connection issue.
Do you have vcds?

I should do a scope output of the hall effect sensor to see what RPM actually idle is at. The value of "903" is a byproduct of 8-bit digitization as the ECU sees a value of 43 and the RPM interval is set at 21. Once multiplied together you get 903. It's simple aliasing.

gatz · Nov 6, 2015

Okay so, we've had the glow plug issues on our 2005 BEW engine off and on for probably 6 years now. Basically they would throw a code every month or two, and it ended up continuously faulting. All of them ohmed out fine 0.6 +/- 0.1 ohms.

Long story short I'm on the third harness, and third set of plugs. First set was replaced by the dealer for the 5V recall, second set see my story below. Anyway, the latest harness and plugs I just put in about 3 weeks ago. I thought it was fixed, since it was CEL on continuously before, and it went off for the first time in a year. Having no CEL at all was nice for few weeks while it lasted, but the damn thing is back on with another #3 cylinder intermittent fault! The same cylinder that it was complaining about before. Should I try replacing the controller? Or maybe the wiring is corroded up near the controller? There are so many threads on this matter but I didn't find any that talked about the wiring at the controller end specifically on the PD which supposedly doesn't have a separate connector. Do they terminate inside a larger connector then?

Finally, a word of warning for others. Out of frustration I found a very old thread mentioned tieing the 4 wires together so they act as one which supposedly would fool the system. DO NOT DO THIS if you have the 5V system / PD engine. They were all ohming fine before, but after this mod all 4 completely burned out (no continuity + failed bench tested afterwards). Checked the voltage coming out of the controller *after* they got fried and apparently this setup confuses the 5V PWM controller and causes it to output 12V continuously. (Maybe it pulses 12V to different wires in round robin, so tieing them together causes 12V across them all?)

where2 · Dec 19, 2015

soldier said:
Wingnut, I know this is an old post just wanted to say Thank You, you Saved me a lot of trouble!!

^^^^^ Exactly my thoughts. My 2004 PD has been intermittently throwing a P0671 code for a few weeks. It hasn't been an issue since it lives in the temperate tropics (South Florida). When I clear it, the code doesn't always recur on the next startup, but it was getting annoying. The real reason I care: On the rare occasion my wife drives my TDI (rather than her's), she comments about the CEL in my car.

This morning, following Wingnut's guide, I pulled my meter out, checked the resistances: #1 was ~10 ohms rather than ~2.5. So, I pulled the #1 glow plug, and was going to simply replace it with a spare I bought years ago. When I checked the resistance of the old plug versus the new plug lying in the driveway, they were identical? Hmmm?? So, I surmise that the connection was "not the best" between the cylinder head and the #1 glow plug. Rather than swap it, I cleaned the threads on the old plug (carbon), and gently reinstalled it. Checked the resistances again when reinstalled, 2.5, 2.4, 2.5, 2.5 ohms (1-2-3-4 respectively). Cleared my CEL again, and we'll see how long it stays off. Boxed up my new glow plug and put it back in the drawer.

My glow plugs and harness were replaced in 2012 (~30k miles ago) due to an open recall.

nailhead2tdi · Dec 20, 2015

Wingnut, thank you the glow plug tutorial. I am especially grateful for the tip on the shrink wrap for exposure. I did not know this existed. I use shrink wrap when ever I do an electrical repair on the equipment I work on. The equipment is not out in the elements. I am ordering the Deoxit D5 and hoping that there is a bad plug! I do not want to have to pick up the heat shrink tubing. Hate to cut!! I'll be getting on the system with my meter tomorrow. All the Best.

Matthewsz · Dec 23, 2015

Hi all, thanks for the tutorial, it helped a lot. However I ran into a problem that I can't figure out. I had 1 bad glow plug giving me a cel, and my harness was kind of a mess so I got 4 new Bosch plugs and oem harness. Car is 03. Now I have no power to the harness, the new wires are good I tested them. Fuses at battery are fine. Got a new Bosch relay, and it didn't fix my problem. Any suggestions?
(I've been reading the forum for years and learned a lot, thanks for all the great threads and diys. I also have a b5 Passat waiting for a kit from Frans, 6speed, Avg engine)

Matthewsz · Dec 26, 2015

Did I post in the wrong thread, I don't want to start a new one for this...

Matthewsz said:
Hi all, thanks for the tutorial, it helped a lot. However I ran into a problem that I can't figure out. I had 1 bad glow plug giving me a cel, and my harness was kind of a mess so I got 4 new Bosch plugs and oem harness. Car is 03. Now I have no power to the harness, the new wires are good I tested them. Fuses at battery are fine. Got a new Bosch relay, and it didn't fix my problem. Any suggestions?
(I've been reading the forum for years and learned a lot, thanks for all the great threads and diys. I also have a b5 Passat waiting for a kit from Frans, 6speed, Avg engine)

MartinsPro · Jan 5, 2016

Hey!
Im having issues with cold start ups. I thought that my glow plugs is bad, so i replaced them with Beru glow plugs. When i changed the glow plugs i somehow looked inside fuse box on the top of battery, the 4th fuse from the right side was blown. Then i found out that 4th fuse is for glow plugs.. I changed the fuse but when i turned the key on to warm the glow plugs, the plastic started to melt and fuse burned off ..
What could cause this?

Golf mk4 tdi AHF

BobnOH · Jan 5, 2016

Follow the wiring back from the fuse, it must be shorted out somewhere

MartinsPro · Jan 5, 2016

BobnOH said:
Follow the wiring back from the fuse, it must be shorted out somewhere

Do understand correctly that circuit goes like this:
from top of the battery through fuse S163 -> cable grove under airbox -> through firewall to the relay -> from relay to connector in cable grove next to airbox-> Again under airbox to the glow plugs.

Is there any typical place where it can make a short?

buttonfly · Jan 12, 2016

Glow plugs, 2004 Jetta Wagon, BEW, 5-speed

I thought I’d throw this in the forum, for clarification and/or to confuse things even more.

At nearly 316,000 miles, my wife was driving the Jetta (’04, BEW) and got the FIRST EVER check engine light. Preventive maintenance has paid off up until this point.

Error code points to glow plugs. I checked Ross Tech and this forum, lots of recommendations to go with part number N10591609, so I check my favorite sites (iDParts, ECS, Bora, and Kerma) and they all also list N10591609 as the current part number.

Then I remember that the Jetta went to the dealer back in ’09 or ’10 for the recall or technical service bulletin service, so I call the dealer (Maple Hill in Kalamazoo). They confirm that they put in new glow plugs and updated the software. The GP that they installed then was part N10591607. I want to make sure the GP I buy is compatible with the software update. They transfer me to the parts counter. I give him my VIN, he tells me that the current GP for me is N10591608. I ask about N10591609, and here’s what he tells me:
N10591607 is a Bosch part, cost about $26, in stock, compatible with the software.
N10591608 is an NGK part, cost about $42, in stock, compatible with the software.
N10591609 is listed by VW as a “catalog referral”, meaning that it is ON HOLD and cannot be ordered by the dealerships, possibly because of warranty issues or other performance problems.

So since the N10591607 failed on me, I am planning to get the N10591608. Any feedback you folks on TDIClub can provide would be appreciated.
I’ll let you know how the GB swap-out goes, and report on the cold weather starting.

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

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Glow plugs 101 Ver. 2.0