Melted coolant glow plugs

guiwang

Active member
Joined
Sep 21, 2009
Location
Minnedosa, MB
TDI
2002 Jetta TDI
So, a friend of mine brought me her car to have some work done and a general check over. I pop the hood, check the oil, start the car and come around to the front too see a fair amount of smoke billowing out from the vac pump area. Shut it down, take a closer look and this is what I find.
http://pics.tdiclub.com/showphoto.php?photo=91782&title=melted-cgp-connector&cat=565
http://pics.tdiclub.com/showphoto.php?photo=91783&title=melted-cgp-connector-2&cat=565
One glow plug boot is completely melted to the bare wire, and the other two boots are partially melted. I did a search and nothing I found showed anything this extreme. I can't imagine how much current must have been running through these wires, and yet no fuse blown.
 

Vince Waldon

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Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
They draw at least 10 amps each, and IIRC are protected by a 50A fuse.

Dirty/rusty/wet connection = resistance = heat. :)

This dirty connection would actually make them draw less current than normal, so no fuse would pop, but the concentrated heat in one spot is enough to melt stuff.
 

guiwang

Active member
Joined
Sep 21, 2009
Location
Minnedosa, MB
TDI
2002 Jetta TDI
They draw at least 10 amps each, and IIRC are protected by a 50A fuse.
Dirty/rusty/wet connection = resistance = heat. :)
This dirty connection would actually make them draw less current than normal, so no fuse would pop, but the concentrated heat in one spot is enough to melt stuff.
Yeah I guess that makes sense. I'm cleaning the intake, egr, and egr cooler right now, so I'll take a closer look later tonight or first thing in the morning.
Btw: 2002 jetta 305000 kms
Thanks,
Gui
 

PDJetta

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Nov 6, 2003
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Northern Virginia
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'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
I've seen this happen on other electrical consummers that are fused/circuit protected. The connection between the glow plug and the connector (power source) is poor (high enough resistance to get hot enough to melt the insulation, but not low enough to draw enough current to blow the fuse).

I would replace the connector and just to be sure, replace the glow plug fed by the connector (perhaps the GP is drawing too much current). Make sure the conector is seating well.

As an option to replacing the connector (it may not be available except as a larger wiring harness) you may be able to solder the supply wire directly to the GP terminal stud and slip heat shrink tubing over it for a neat job. I'd replace the GP first, though, as a precaution. You may want to first extend the wiring a little to make room for future repair jobs involving components in that area, like the vacuum pump, since the wire can not be simply unplugged after soldering.

I'd also verify that the GP relay is not stuck on, supplying power all the time. I believe when the coolant is at temperature the coolant GPs are supposed to be off. The relays for them are under a cover behind the battery, I believe.

--Nate
 

JB05

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Oct 20, 2005
Location
Il.USA
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Golf,2005,anthracite blue
There are two relays that control the coolant GP's and they are located on the fire wall, left side, behind the curved plastic conduit type casing. IIRC, all three GP's do not turn on all at once, but depending on ambient temperature, maybe one will turn on, or maybe just two at a time, but I'm not certain.
 

guiwang

Active member
Joined
Sep 21, 2009
Location
Minnedosa, MB
TDI
2002 Jetta TDI
Hi
Thanks for the replies. Looked a little closer today and here's what I found.

Gp#1 .3 ohms
Gp#2 .2 ohms
Gp#3 2.1 milli ohms.
As I understand it, this means they are good, but I am curious as to why #3 has so much lower of a reading than the other two.

Gp #1 & #2 were being powered from J360 (relay100) and it was gp #2 that had the boot completely melted off.
Gp #3 powered by J359 (relay 53)
Removed and bench tested both relays and they appear to be working fine. Chalk it up to a bad connection I guess? I'm thinking I will solder in 3 new boots, and once I have the car back together make sure that the gp's are being shut off once the car reaches op. temp.

Thanks
Gui
 

Vince Waldon

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Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
I think you're on the right track... nice clean connections and you should be fine...

Except...those readings do seem a little wonky. Given that they draw around 10 amps I would have expected them to be in the 1.5-2 ohm range, like the engine glow plugs.

And, 2.1 milliohms is essentially a dead short. :)

When you connect the two leads of your multimeter together what reading do you get?
 

guiwang

Active member
Joined
Sep 21, 2009
Location
Minnedosa, MB
TDI
2002 Jetta TDI
I think you're on the right track... nice clean connections and you should be fine...
Except...those readings do seem a little wonky. Given that they draw around 10 amps I would have expected them to be in the 1.5-2 ohm range, like the engine glow plugs.
And, 2.1 milliohms is essentially a dead short. :)
When you connect the two leads of your multimeter together what reading do you get?
Hey,
Multimeter leads connected together give a reading of 0.0 ohms.
Am I correct in thinking that measuring the resistance through the GP's in a dead circuit doesn't accurately represent the actual resistance in the live circuit? Does resistance not increase (i.e. amperage drop) as the temperature of a conductor increases (GP's heating)? So the only true was to figure out the resistance of this circuit would be to measure current and voltage of the powered circuit, then calculate the resistance.
Anyways, should I be looking at changing all three GP's or just the one?
Thanks,
Gui
 

Newflee

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Joined
Jan 7, 2011
Location
Canada
TDI
New Beetle TDI
wouldn't worry about them. I would cut off any harness that you felt was shorting out though. Mine are all 3 dead and I'm not spending 30 bucks each for them. I got a Frostheater and have never had a batter winter car. -25 and I get in start up and turn the heat on......period.
I use it any time below zero just to be easy on the car but she heats up to engine operating temps even at the dead of winter so be careful. Oh ....I'm from down the road in winnipeg so I know what winter is like too....;)


ok if your into plugs.......they are all ok.....if they were dead they would be reading infinite so 1.0-2.0 is just fine. They aren't monitored by the ECU like the block cylinder plugs because they are bogus.....just like the EGR is bogus as far as helping to warm up the engine in our climate. I actually have one that is good out of three and I could care less....however if you want to trade a case of Lucky for it.....I'm game.....just bring your dead one because the lucky empty won't screw in there.
 
Last edited:

guiwang

Active member
Joined
Sep 21, 2009
Location
Minnedosa, MB
TDI
2002 Jetta TDI
I'll go with Vince on this one. Milli=1/1000, so 2.1 milliohm=.0021 ohm
Paul
Yeah, definitely almost a dead short.
Newflee- thanks for the offer but after a little digging around in the garage, I found an extra coolant flange with 3 GP's in it. All tested to .4 ohms, so I will likely change out the GP with the weird reading and keep an eye on the other two.
Boots to be soldered in should be here tomorrow.
Gui
 

Newflee

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Joined
Jan 7, 2011
Location
Canada
TDI
New Beetle TDI
Cool.....just to let you know...your pretty close to me should you need vagcom and not already have it, shoot me a pm.
 

bigblue

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Joined
Feb 12, 2007
Location
NJ/nyc
TDI
2003 jetta ALH, 2004 golf pd150
I know this thread is almost 5 years old but I wanted to revive it because I just noticed the exact same issue on my 2003 Jetta and I haven't found other posts mentioning this issue. One of the wires appears to have completely burnt itself off the connector. No CEL and the car has always started and run properly in cold weather, though perhaps this is why heat has always been very slow to warm compared to my previous AHU B4 cars.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I believe there is no CEL for their function.
Simply refresh, clean insulate or renew the wires. Replace plugs if necessary. They can even be safely eliminated
 

Genesis

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Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Just leave 'em disconnected; they won't throw a code as you've seen and they're NOT why you are not warming up reasonably rapidly in colder weather. That's probably a bad thermostat.
 

turbocharged798

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Joined
May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
Found mine burnt out and after replacing them it made a huge difference in warm up time. I threaded the tops and used ring terminals so there is no plug to melt and start a fire. They give just enough heat to the cabin to take the chill out.
 

wonneber

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Joined
Oct 12, 2011
Location
Monroe, NY, USA
TDI
2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
I agree with its shorted.
I am a fan of amperage testing on high power things like this.
I use a clamp on the wire amp meter and an old push button starter switch.
I clip on the battery terminal, lay the amp gauge on that wire and the other clip to the device being tested.
I quick tap the button and watch if the gauge pegs or just moves a bit.
If it pegs I do not press it again.
 
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