Glow plug harness, declaration of victory !!

[weasel]

Well I made the damned thing. CEL still wouldn't go away. So I took the chance and wired it so that I now effectively have a one wire harness. Complete success, no CEL

I still have to get some wire loom to protect it, but it will do until I can drive to the parts store.

Just to recap. 8-32 threads on the ends of the GP's, brass washer ring terminal, brass washer, lock washer and brass nut. End of problem.

 

[mavapa]

So, if I understand correctly, there is essentially one wire feeding all the glowplugs, thus eliminating comparison among them and keeping a CEL code from appearing?

 

[weasel]

Exactly. And it still appears to be working just fine.

 

[OmegaRenegade]

If this works out nicely maybe a How to DIY is in order!

would definatley be interested in making something like this myself if its gonna increase the life of my GP's and keep that pesky CEL away!

 

[weasel]

If you know how to crimp on connectors and swing a thread die, they How-To almost writes itself. All you have to do is remove the glow plug, thread the end to 8-32. You'll need a total of 8 x #8 washers, 4 x 8-32 nuts and 4 lock washers. For the crimp connectors I had, I had to bundle wire from GP's #1 & 2 together and #'s 3 & 4 together. I then ran a short piece from each of those and twisted them together. I twisted together the two supply power wires together. Crimp the pair from the GP's to that. If you can mentally picture a tri-y header you'll see what I mean. I forgot one thing. I used 12gauge wire. Way bigger than I needed. Probably 14 or 16 would be enough.

 

[ymz]

Shame on you !!!!!

SAE threads on a German car....

tsk... tsk... tsk...

Yuri.

 

[jackbombay]

Glad to hear you got it sorted out!

When my GP harness quits I'll do the same thing, but metric

 

[Doug Huffman]

The curse of GPs is corrosion. How'd you do (on) material selection? Bimetallic corrosion down the road, so to speak? Not to mention good ol' rust. Remember the 'wash the engine' debate and (not so) Simple Green and aluminum?

 

[Wingnut]

I'm glad it worked for you. But you could have gotten the same results with much less work. Simply strip a half inch off each of the original harnees wires. Then twist the harness to bridge the 2 wires. Then coat the connection with some liquid electrical tape to seal out any moisture.

Bridging the two wires would have done the same thing as your setup, essentially tricking the ECU into thinking there is no resistance difference. It can't compare two resistances if they are both the same.

But kudos to you for going through with it. Many have thought about doing this, but few have tried it. Please let us know how it works out.

 

[jaydhall]

"It can't compare two resistances if they are both the same."

Sorry, being an engineer, I have to say that it CAN and DOES compare the two resistances. However, being the SAME there can be no difference and it is happy.

 

[big monkey fight]

I'd like more than victory

My situation sounds similar to weasel's and I will probably end up bridging the two wires before the glow plug harness (especially since it seems to work), but would like to restore the circuits to their rightful place with full sensing capability.

I worked through wingnut's glow plugs 101 (http://forums.tdiclub.com/showthread.php?t=79819&highlight=glow+plug+harness+how-to) and found that:

-the glow plugs are fine.
-harness seems fine
-I only get voltage to one of the two wires.

I've tried tracing the wires back to a connection too see where the open circuit is, but that gets a little involved after removing the battery mount. I can't find the glow plug relay which is where the lines lead according to my Haynes manual's circuit diagram. Any suggestions?

thanks. bmf

 

[weasel]

Wingnut: You are exactly right,however, I was convinced my harness was the culprit to begin with. Without a really accurate way to test a harness, making one was my only sure option.

Oh and the reason I went with an SAE thread ? Made better sense. I have a conversion chart for my tap and die set and the diameter of the GP was a better fit to an 8-32. M4 was the other option ( only a few thousands of an inch difference )

 

[Birdman]

That is sorta the way the early diesels 1978 and up a lot of years did their glow plugs. They just ran a single bus bar to all the plug to to the relay. the only problem with the old way and is what makes yours better. You can check yours one at a time where we had to remove the whole bus bar a real PITA. Nice job.

 

[oilhammer]

The PD Passats have 4 separate leads, perhaps someone could find the part # for that harness and it could be retrofitted to the older cars. That way you'd still have your simple pop-on/pop-off connectors.

Local guy here (electrician, go figure... ) just installed some heavy duty resistors behind the relay block in the fuse panel where the glowplug ECU lives, then put the glow harness connectors to a wire going to a solenoid operated switch (like a starter solenoid some Fords use) on the firewall, and manually controlled them with a button on the steering column.

The reason these glowplugs fail is the tremendous long afterglow period, for "emission" purposes. Unlike the old diesels, that afterglowed for maybe 10 seconds, TDIs will afterglow for several minutes when cold as long as the engine is below 2500 RPM. Pre-'02 cars you can here the relay click off and on when cold when you rev the engine over 2500 RPM and let it come back down. That is another reason why it is so important when cold to start the car and drive off immediately and keep the RPMs over 2500 as much as you can. The engine will warm up faster and the darn afterglow won't drag on!

 

[BugBug]

This is a great fix for the repeat GP harness failure. Now, the ECU won't be able to let you know if you do in fact have a bad GP. Do you test them occasionaly?

 

[oilhammer]

That is a good point. However, if one is observant he/she will notice how the car starts cold and if there is a bad miss or stumble accompanied by lots of white smoke after a cold start you'd know to investigate.

I've put nearly 1 million miles on old diesels that had no such glowplug monitor, drive one every day, and I've never had a no-start. I think the main reason it is there is for the EPA...

 

[weasel]

Agreed with oilhammer. If one plug isn't working, you'll know ...

 

[vetaylor6]

Any other suggestions

Any suggestions after completing this repair and going through glow plugs 101, I still have the stupid check engine light. Any negative terminals that would be good to check for corrosion? I am tired of the check engine light. I just fixed the ABS sensor to finally get that light to disappear and I am working on getting the check engine light to go away.

Also, I need to get this fixed based off of the emissions checks for diesels. I am moving to the Pittsburgh area and I will need to get an emissions check, so I need to get the error codes removed.

 

[jackbombay]

You connected all 4 wires (2 if you have an older model) together
and you still have the CEL?

I threaded my GPs and still had the code even though the GPs were bad, today I went all out and connected all the GP leads together, no mre CEL

 

[vetaylor6]

I wrapped the 2 furthest glow plug wires together, then the 2 closest glow plug wires and then wrapped all of them unto the factory wires. I do need to check the voltage again on each of the outlets to make sure each is getting at least 12 volts. What is weird about it is that I can clear the code, and I can drive wherever, and then when I start it up the next time is when it seems to throw the code again. I was wondering if I need to check for grounds though too, and find out if they are corroded. I wanted to know where the ground might be located pertaining to the glow plugs.

Thanks for the suggestion jack. I really want this fixed.

 

[jackbombay]

So all 4 wires have been stripped and soldered together then they were attached as a whole to the factory harness? If not, that's what you need to do. If that's what you did I am REALLY puzzled as to the source of your problem.

 

[mrGutWrench]

So all 4 wires have been stripped and soldered together then they were attached as a whole to the factory harness? If not, that's what you need to do. If that's what you did I am REALLY puzzled as to the source of your problem.

__. Me too. Should be impossible to cause. Is it a fer-shure GP code?

 

[Wingnut]

Any suggestions after completing this repair and going through glow plugs 101, I still have the stupid check engine light.

Please forgive me for asking this question, but have you had the light cleared with a scan tool? It will not go out on its own if the problem is fixed.

 

[vetaylor6]

This was part of the problem, I just finally bought a VAG-COM, and I replaced the wiring harness about 2 months ago. So I cleared the P0380 (Glow plug/heater circuit electrical fault (Q6)) code thinking this thing would finally be fixed, only to have the Check Engine light come back on. So I did the resistance check of the glow plugs to find the one nearest the fuel filter had a resistance of 6 while all others only had 1._, I also removed the fuse on top of the battery and cleaned any corrosion off of it. I still need to check the voltage coming out of each of the outlets to the GPs to ensure that the voltage is above 12V. I pulled the relay and took the cap off of it to make sure none of the soldering was cracked. As for the actual harness, I wrapped all of the wires together, 4 going into 1, but did not solder. So I imagine the are getting connection right now, but I do need to solder them to ensure that they stay together. I am going to check voltage when I get home this evening and report back for anymore suggestions.

 

[DPM]

Have you replaced the faulty plug?

 

[vetaylor6]

I replaced the faulty plug hoping that would finally take care of the problem. I looked through the wiring and found the wiring had pulled apart and that is why the code was being thrown. So, FINALLY VICTORY, but I still need to solder it, which won't happen until August when I move back to PA. But at least I know the problem and can fix it if the check engine light comes on again. Thanks to you guys for your help and suggestions. It is definately nice to have the VAG-Com to clear the codes.

Thanks Again for the help and suggestions. But I am glad to finally have it figured out. I just get to look forward to tearing into it again to solder it when I get back to PA and get my soldering iron.

 

[jackbombay]

Where was the wiring pulled apart?

 

[weasel]

I can't believe this thread came back to life. Its a good thing that the diy harness works. Solves a whole bunch of problems all at once. I haven't had an issue since I did mine.

 

[Uncle_Dave]

I have 120 K miles and have started to get codes. Having had a Rabbit, I was thinking of threading the glow plug and using a ring crimp on. I got so far as threading an old GP, but did not like the threads that I was able to make, and thought that the nuts were too easy to strip off.

The post on the Glow Plug seems to be Stainless Steel, I tried solder, but it would not take. The Harness connector is some sort of spring metal, and when it gets hot with the 15 amps or so, it is going to corrode and not be a spring much longer.

I came across a wire nut with pigtail about a foot long. This sent me back to the Treading idea. The post is smooth, and the wire nut will not grip it as such. But what would happen if it were threaded? Then the wire nut should grab that post very nicely. A short length of the pigtail, and a spayed crip on, and you should be all set. The glow plug should last for about 100K miles.

Threading the post, and using more than one nut. Lock washers between them should give a little more tension on the lug.

Problem as I see it. That post is Stainless Steel. Were I work we use this for the hardware, Why? it does not rust. We also use aluminium, why? again, it does not rust. But you put Aluminium against Steel, and you have all sorts of problems!!! Like connectors on Glow Plugs!!! To stop this we have been using Di electric paste for some time now.
The Mag Wheel on the Axle trick. Took 2 1/2 hrs for AAA to show up!!

Have also been thinking of tying the leads together.

Permatex Battery Post protector kept my CEL off for about 40K miles. Then I had a GP fail, and changed them all as a set.

Best test that I have seen to check a GP is to put a Battery Charger on them, and read the currents. Do it Quickly in about 1 second they are going to Glow Red!

 

[weasel]

Mine ( IIRC ) go one washer, ring terminal, washer, lockwasher and nut. All are brass and have dielectric grease on them. No corrosion at all and no glow plug problems since. If I ever do have to remove the harness for some reason, I have a conductive grease that will go on instead of the dielectric.

As far as testing goes, you don't even need to read the current. just hook straight to a battery and watch the glow. Either they will or they won't. Multimeter works just as well too and you don't risk a nasty burn.