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

Dieselista

Active member
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May 1, 2008
Location
Virginia
TDI
06 Jetta, 03 Bug, 74 TR6, 92 Ducati 907ie, 96 F250 PowerStroke

OwenWS25

New member
Joined
May 5, 2019
Location
PNW
TDI
2004 Golf TDI
I have been having some issue with starting up my '04 Golf TDI.

First started when I tried to turn it on without waiting for glow plugs to light up, now happening every once in a while even after waiting. When it doesn't start the glow plug light turns on then keeps flashing. Noticed it might be better after letting glow plugs heat up for longer. And I have started it a few times while the glow plug light still flashing. Pulled codes, but doesn't look like they have to do with this issue.

19463
16706
16792

I tested the glow plugs and all ohm values were around 0.8. I tested the wiring harness and got 5v running through all 4 points.

Is this a low voltage? Or is that converted for 5v glow plugs?

If it is low, would that be the wiring harness, or I heard it could be a relay?

Could use some advice on how to proceed.

I also tested the fuse block on the battery and all checked out.

Thank you.
 

matt002

New member
Joined
Sep 16, 2019
Location
UK
TDI
VWT5
Hello all,

I have followed the 101 guide and would like to replace my glow plug harness next.

I have a VWT5 with a 4 wire harness.

Is there any reason why I cant soldier connect in a new 4 wire harness of the correct type same as for the 2 wire as described in the 101 guide? I am assuming that the 4 wires are individual +ve supplies to each of the glow plugs and I may need to do some trial and error using VCDS to ensure i get the correct connections prior to soldering and sealing.

The 101 guide states that the 4 wire version is more involved, Am I missing something?

Thanks
Matt
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Yes, you can hook it up many ways and it will work. But I would remove the battery, the air box and replace all the way to the connection in the duct. If you cut and splice, just tag the wires to get them matched, then your future codes will be accurate.
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
Some models / years have the 4 wire harnesses reporting glow plug order as the reverse of the cylinder numbering... (for a valid reason - although that tends to confuse people...) You may wish to arrange it so that it reads the way that makes sense to you...


Y.
 

gunnerthesnowman

Well-known member
Joined
Jul 26, 2016
Location
Alberta Canada
TDI
2004 diesel jetta
Hi All , I have a 2004 tdi and it starts hard when cold, one thing I notice no matter what the outside temp is, the glow plugs only cycle for about 3 seconds and for that 3 seconds the voltage only test 8.9 volts and the harness end that connects to each glow plug and then it drops to 2.3 volts.
I will disconnect the coolant temp sensor and see if they stay on for the 20 seconds , I will also check the fuses on top of the battery and report back here.
 

gunnerthesnowman

Well-known member
Joined
Jul 26, 2016
Location
Alberta Canada
TDI
2004 diesel jetta
Ok, I disconnected the coolant sensor and there is no different in the time the glow plug power stays on , about 3 seconds???
I shot Wingnut a PM (hope he does not mind a pm on this )
Hoping to get this working right as winter is coming fast here in Alberta
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
The 2004s had at least one recall concerning the glow plugs... first they came out with ceramic ones that tended to break, then they put in some metal-tipped ones - at a different voltage - that never quite worked properly... I believe _some_ cars also received yet another update to a different style of ceramic tipped plugs - at yet another voltage... so... first check with a dealer to see whether your car has had the update(s)...
 

gunnerthesnowman

Well-known member
Joined
Jul 26, 2016
Location
Alberta Canada
TDI
2004 diesel jetta
Can I tell with VAG COM if I have the updates ?, also with VAG COM can I change the glow plug voltage setting ?
Thanks


The 2004s had at least one recall concerning the glow plugs... first they came out with ceramic ones that tended to break, then they put in some metal-tipped ones - at a different voltage - that never quite worked properly... I believe _some_ cars also received yet another update to a different style of ceramic tipped plugs - at yet another voltage... so... first check with a dealer to see whether your car has had the update(s)...
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Can I tell with VAG COM if I have the updates ?, also with VAG COM can I change the glow plug voltage setting ?
Thanks
You can not change the voltage, you can change the length of time they stay on. There should be data in the header when you connect the VAGcom, sorry, you'll have to research what to look for.
I WAS CORRECTED, YOU CAN NOT CHANGE THE TIME IN A PD SETUP- thanks turbovan
 
Last edited:

rhinorear

Well-known member
Joined
Jul 27, 2019
Location
Lost Causes NM
TDI
2014 JSW
Hi All , I have a 2004 tdi and it starts hard when cold, one thing I notice no matter what the outside temp is, the glow plugs only cycle for about 3 seconds and for that 3 seconds the voltage only test 8.9 volts and the harness end that connects to each glow plug and then it drops to 2.3 volts.
I will disconnect the coolant temp sensor and see if they stay on for the 20 seconds , I will also check the fuses on top of the battery and report back here.





Like you I had the same concern about glow plug cycle time on my 2014. Thinking that no matter what the temp was the cycle would stay the same. I was relieved that with a 27 degree morning my plugs stayed on for a considerable longer time period.



I think you're on the right track thinking there is something wrong. Hope you get it figured out.
 

turbovan+tdi

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Mar 23, 2014
Location
Abbotsford, BC.
TDI
2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
You can not change the voltage, you can change the length of time they stay on. There should be data in the header when you connect the VAGcom, sorry, you'll have to research what to look for.
You can't change any PD settings for GP's, only a tuner can.
 

turbovan+tdi

Top Post Dawg
Joined
Mar 23, 2014
Location
Abbotsford, BC.
TDI
2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
Ok, I disconnected the coolant sensor and there is no different in the time the glow plug power stays on , about 3 seconds???
I shot Wingnut a PM (hope he does not mind a pm on this )
Hoping to get this working right as winter is coming fast here in Alberta
The BEW's don't need much gp time to work, but I had Malone extend mine as it started ok, but then would chug for a few seconds, then smooth out. My factory setting would start at -20 deg c with a weak battery.


Can I tell with VAG COM if I have the updates ?, also with VAG COM can I change the glow plug voltage setting ?
Thanks
You can see what gp's you have with VCDS, can't remember where to look. I'll ask Malone later.

Also, pull a gp, it will say 5 or 7 volts on it.
 

gunnerthesnowman

Well-known member
Joined
Jul 26, 2016
Location
Alberta Canada
TDI
2004 diesel jetta
The BEW's don't need much gp time to work, but I had Malone extend mine as it started ok, but then would chug for a few seconds, then smooth out. My factory setting would start at -20 deg c with a weak battery.




You can see what gp's you have with VCDS, can't remember where to look. I'll ask Malone later.

Also, pull a gp, it will say 5 or 7 volts on it.
I read every post in this tread and anywhere that the glow plug voltage was talked about it was always 12 volts !
 

turbovan+tdi

Top Post Dawg
Joined
Mar 23, 2014
Location
Abbotsford, BC.
TDI
2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
I read every post in this tread and anywhere that the glow plug voltage was talked about it was always 12 volts !
Not a BEW, this thread is for ALH. BEW's came with 2 voltages, neither of them were 12 volts.
 

turbovan+tdi

Top Post Dawg
Joined
Mar 23, 2014
Location
Abbotsford, BC.
TDI
2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
Ok, but when I look up the glow plug part # it takes the same glow plug as my 2006 TDI?
2006 is PD, if its a MK5 platform, so yes, it will take the same gp.
 

ktmjammer

New member
Joined
Nov 14, 2019
Location
Memphis
TDI
2006 beetle tdi
2006 tdi beetle glow plug harness.

I have a 4 wire glow plug harness that needs replacing.Why do many people go the hard rout of removing the air box ,battery .....to replace the total wire as opposed to splicing in close to harness.
 

ktmjammer

New member
Joined
Nov 14, 2019
Location
Memphis
TDI
2006 beetle tdi
2006 tdi beetle glow plug harness

what is the best way to replace the glow plug harness on a 4 wire set up
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
what is the best way to replace the glow plug harness on a 4 wire set up
Pull the battery and air box, the new bit will plug in inside the duct that runs behind the air box. However, many folks just splice it in up near the engine.
 

ktmjammer

New member
Joined
Nov 14, 2019
Location
Memphis
TDI
2006 beetle tdi
Glow plug harness

the harness i bought does not have a plug on the end so i will have to splice either way.
 

RussR

New member
Joined
Nov 22, 2019
Location
North Pole, AK
TDI
2004 Jetta TDI
2004 Jetta glow plug issues

Hello everyone. I am in need of some help trying to figure out my glow plug issue on my 04 Jetta. First off, ive been all over the internet trying to find anything helpful, and this forum site has been the most help with information, procedures and fellow owner advice.

I do not have a CEL. The glow plug circuit seems to be intact. The harness is good, the fuses and connections are all clean with no corrosion. The glow plug harness is also clean with no corrosion. When I cycle the key, the glow plug light comes on for 1-2 seconds and goes out. Ive disconned, inspected and cleaned the coolant temp sensor connector. With it disconnected the light will stay on for 3-4 seconds. All 4 glow plugs are reading .2 ohms and are new. Voltage readings at all glow plug connections is only reaching 7.84 volts before the system cycles off. I disconnected the relay and did get a CEL. Sooo I figured I had a bad relay Replaced the relay and still have all the same results... I’m at a loss now, and am not sure where to go next. Closest dealer to me is 360 miles away. I should mention that my car is a manual transmission car. The coolant glow plugs appear ok, but since I understand they aren’t monitored by the ECM, I haven’t spent much time on them... anyone have a similar experience, or know where I need to go next? Thanks sooo much for all the help and information so far....
 

ymz

Top Post Dawg
Joined
May 12, 2003
Location
Between Toronto & Montreal
TDI
2003 Jetta TDI Wagon, 2003 Jetta TDI Wagon
What is your issue? Hard starting? There are different types if glow plugs (different voltages), and you need to know whether any recalls / updates have been made to your car... perhaps the dealer can tell you over the phone if you give them your V.I.N...
 
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