Check your coolant glow plugs!

turbocharged798

Veteran Member
Joined
May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
I was repairing an unrelated wire on my 04 PD when I remembered that somebody on these forms nearly had their car catch on fire due to a bad connection on the coolant glow plugs. Well, I went to check mine and holly $#!@, the one nearest to the rear of the car has a completely melted tip.:eek: I know it still is working, because when I unplug it, the engine tone changes due to the electrical load change. The other three were fine. it appears that the base of the glow plug is loose and creating a bad connection.

I just unplugged it for now, but I am probably just going to replace the glow plug and possibly the connector as well.


 

procupine14

Veteran Member
Joined
May 20, 2010
Location
Kansas City, MO
TDI
2003 Beetle 5sp
Wow.....I checked mine when I bought my Beetle and I had to fix one of my wires as it was hanging on by a thread. The other two were in good shape though!
 

WantingaTDI

Veteran Member
Joined
Jul 25, 2003
Location
Washington DC (moved from VT)
TDI
VW Golf 03 TDI
Do the coolant glow plugs come on when you turn the key to the accessory position along with the fuel glow plugs? And will they throw a CEL if they aren't properly connected?
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Do the coolant glow plugs come on when you turn the key to the accessory position along with the fuel glow plugs? And will they throw a CEL if they aren't properly connected?
They come on like the combustion ones do upon cold start when coolant is below certain temp and then they stay on during operation until the coolant reaches the pre-determined temp (don't recall how warm).
The ECU doesnt monitor whether they are working or not, so they don't throw a CEL.
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
028 971 782A-Angled connector with harness glow plug. 3 required to replace all. There are only 3, don't know what statement in post 1 means.

$27.35 at IMPEX

This connection I would probably solder and heat shrink.
 

PDJetta

Top Post Dawg
Joined
Nov 6, 2003
Location
Northern Virginia
TDI
'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
Me too. I would not pay $27 plus shipping for a connector.

My coolant GPs and connectors are in great shape and show continuity, but I have no idea if they ever come on. It would be nice to have some sort of LED indicator hooked into the circuit to see when they are getting power. Perhaps a different LED color of each one, mounted on the dash.

--Nate
 

NarfBLAST

Top Post Dawg
Joined
Mar 3, 2002
Location
Waterdown, Ontario, Canada
TDI
2001 Golf 5MT
Just solder the wire directly to the plug you mean, right?



It would be nice to have some LEDs that came on in brightness that reflected the actual current flowing to each glow plug also... I had some fun with a cheap Amp meter with a 30amp scale testing my glow plugs outside of the car and finding that they start off around 20amps when cold then slowly come down to 10amps or when glowing red hot. So in THEORY a circuit might be designed that would give you a glowing indication on an LED of how much current the plugs are drawing, with the LED being possibly twice as bright when cold then coming down. This we you could compare all four cylinder head glow plugs against each other and see if one is failing to draw the same amount of current. I think this would be more accurate then measuring their cold resistance with a few milliamps of current from a multimeter.
 

PDJetta

Top Post Dawg
Joined
Nov 6, 2003
Location
Northern Virginia
TDI
'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
"Just solder the wire directly to the plug you mean, right?"

Looks like that would do it. Add a little shrink wrap tubing ahead of time and you'd be set.

FYI, I just looked at the wiring diagram in my Bentley and the ECU controlls two relays for the coolant GPs. There is a "low temp" and "high temp." relay. The low temp controls one of the GPs and the hi temp relay controls two GPs in parallel (they come on at the same time). So I suppose either the low temp relay can be on, the hi temp, or both. That way you can have 1, 2, or 3 plugs on at once (or none of them). The plugs get their power through one of the 50 amp fuses on top of the battery. They are grounded via their case in the coolant flange. One of the main power relays in the car provides fused power to the "+" side of both realys' switching coils (the other side (ground) of the switching coils in the GP relays each go to a different terminal on the ECU). I have no idea what prameters are used, or under what conditions, the ECU switches the coolant GPs on. I assume all three are the same wattage.

--Nate
 
Last edited:

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon


The coolant plugs don't come on until after the engine starts, and only if ambient is below about -5C *and* coolant temp is low as well (haven't quite determined what value...every drive to work is a new experiment!). Only one coolant plug comes on (first coolant plug relay which is connected to only one plug) if the glowplugs are also running (probably to save load on the alternator) and then as soon as the glow plug after-run is complete the other two coolant plugs come on via the second coolant plug relay. They stay on till the coolant hits 50C.
 
Last edited:

Farfromovin

Torque Addict
Joined
Apr 9, 2005
Location
Ventura, CA
TDI
03 Golf 2dr- PD150 6m
When I bought my German half cut Golf, the coolant plug wires were completely melted. I've just haven't used em ever. Maybe now that Bruce posted a pn I can repair these bad boys. Mmm, quicker morning warmups!
 

PDJetta

Top Post Dawg
Joined
Nov 6, 2003
Location
Northern Virginia
TDI
'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
The coolant plugs don't come on until after the engine starts, and only if ambient is below about -5C *and* coolant temp is low as well (haven't quite determined what value...every drive to work is a new experiment!). Only one coolant plug comes on (first coolant plug relay which is connected to only one plug) if the glowplugs are also running (probably to save load on the alternator) and then as soon as the glow plug after-run is complete the other two coolant plugs come on via the second coolant plug relay. They stay on till the coolant hits 50C.
Perhaps this is why when I started my car at 23 degrees F it seemed to warm up about 8 minutes faster (as determined by the pointer in the temp guage at 190 degrees) than when I started it at 33 degrees F on my drive home from work the past two days.

--Nate
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Some nice creative dash mods there Vince. Good use of o-ring material around the SG. Do the toggles control the GPs, or just the indicator leds??
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
The coolant plugs don't come on until after the engine starts, and only if ambient is below about -5C *and* coolant temp is low as well (haven't quite determined what value...every drive to work is a new experiment!). Only one coolant plug comes on (first coolant plug relay which is connected to only one plug) if the glowplugs are also running (probably to save load on the alternator) and then as soon as the glow plug after-run is complete the other two coolant plugs come on via the second coolant plug relay. They stay on till the coolant hits 50C.
....and the coolant glowplugs cut off below a certain RPM. For some reason, 2200 RPM comes to mind, but may be wrong. In any case, they do not function at idle.
 

turbocharged798

Veteran Member
Joined
May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
....and the coolant glowplugs cut off below a certain RPM. For some reason, 2200 RPM comes to mind, but may be wrong. In any case, they do not function at idle.
They do function at idle. My PD's coolant glow plugs were. You can hear the engine change tone when I unplugged them due to the load change. All three were working when I did the test.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
....and the coolant glowplugs cut off below a certain RPM. For some reason, 2200 RPM comes to mind, but may be wrong. In any case, they do not function at idle.
Cylinder glow plugs turn off above 2500 rpm. There's no low rpm cut off for either cylinder or coolant plugs.

Disconnecting the coolant glow plugs is often a way of stopping the cold idle squeal from a failing harmonic damper. The added alternator load (from coolant heater consumption) makes more resistance on it's drive belt. Sometimes lessening the alternator load is enough to stop the damper from slipping and squealing.
 
Last edited:

TDI-TT

Veteran Member
Joined
Jan 18, 2007
Location
Halton
TDI
2004 Getta TDI
can someone please provide a link to where i can buy these coolant glowplugs for my bew?
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Some nice creative dash mods there Vince. Good use of o-ring material around the SG. Do the toggles control the GPs, or just the indicator leds??
Yeah, the o-ring's recycled from an oil change... perfect fit. ;)

The switches are actually unrelated to the plugs... one controls whether the little LED gauge on the right is reading oil pressure or oil temperature, and the other turns on the brake lights... lots of tailgaters where I live. :D
 

PDJetta

Top Post Dawg
Joined
Nov 6, 2003
Location
Northern Virginia
TDI
'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
can someone please provide a link to where i can buy these coolant glowplugs for my bew?
Well, I thought IDparts.com had them, but the ones they list are for the ALH only, according to their listing. I thought they would have been the same for the BEW.

--Nate
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Perhaps this is why when I started my car at 23 degrees F it seemed to warm up about 8 minutes faster (as determined by the pointer in the temp guage at 190 degrees) than when I started it at 33 degrees F on my drive home from work the past two days.

--Nate
This guy ran a few tests and figured he got about 30% faster warmup to 50C:

http://forums.tdiclub.com/showthread.php?t=269731&highlight=coolant+warmup+time

Now that I have some lights I'll probably mess around with a manual override so that I can run 'em up to 60C etc... man... really need to get a life.
 

Dimitri16V

Top Post Dawg
Joined
Jan 30, 2005
Location
DE
TDI
01 Golf, 04 Golf
Well, I thought IDparts.com had them, but the ones they list are for the ALH only, according to their listing. I thought they would have been the same for the BEW.

--Nate
I believe they are.
 

sqhschief

Veteran Member
Joined
Sep 28, 2008
Location
Tennessee
TDI
2000 Jetta TDi, 1981 Chevrolet LUV Diesel! Non-turbo :(
I don't know why the automatics don't have coolant GP's. Anyone?
 
Top