Manual Glow Plug Switch

Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
For whatever reason, my glow plug system does not work correctly. I have tested just about everything, plugs, harness, CTS sensor, swapped out the GP relay and ECU, and the GP light stays on for only a second before going out, even with the CTS unplugged. So I think I want to wire up my glow plugs to operate manually. I want to install a cabin button to activate them. Does anyone have any insight on how this could be accomplished while not causing a CEL? I have searched but not found much information on this.
 
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
Thanks for the post. The question here is not how long they should stay on. When its 5-10 outside they should definitely stay on for more than 2 seconds by the way. The issue is that no matter how cold (even 0) they do stay on for more than a second, if they are even actually on. I am about done looking for the issue, and just want a manual setup.
 

40X40

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Feb 12, 2006
Location
Kansas City area, MO
TDI
2013 Passat SEL Premium
Is the light intended to stay on as long as the glow plugs are operating, or is the light going out an indication of 'ok to start'? IDK.

Go see a guru.

Bill
 

turbocharged798

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May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
The light just mean OK to start, it does not necessarily run with glow plug operation.

If the light is not staying on when you unplug the CTS, then the ECU is not seeing the correct temp. If the ECU is not seeing the correct temp, then you will have a lot bigger issues than the glow plugs.

At that point, I would connect VCDS and see what the ECU is reading for coolant temp when the CTS is unplugs. It should be something ridiculous (-40*F IIRC).
 

n1das

TDIClub Enthusiast, Veteran Member
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Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
Is the light intended to stay on as long as the glow plugs are operating, or is the light going out an indication of 'ok to start'? IDK.

Go see a guru.

Bill
I second Bill's recommendation to go see a TDIclub GURU in your area.

I'm not a guru but I'm somewhat familiar with the GP behavior. On 2002 and 2003 TDIs (ALH engine), the GP light is an OK to Start light. The GPs actually stay on up to about 10 seconds longer if you wait longer. There is no need to cycle the key to get extra glow time.

The 2002s and 2003s have a 4-wire GP harness and a solid state GP relay. You won't hear this relay click because there are no moving part(s) inside and the relay is located under the windshield wiper cowling. IIRC, the change from the older 2-wire GP harness to a 4-wire harness was due to changes in OBD-II requirements which now require individual monitoring of system components (can't monitor components as a group).

Older TDIs prior to 2002 (not sure about 2001) had a 2-wire harness and a mechanical GP relay. IIRC, the GP light on the dash showed when the GPs were actually ON and you could hear the GP relay click on or off.

In my 2002 Golf TDI (sold it in 2010), one trick I would do in the bitter cold weather was keep the driver's door open when I turned the key. Keeping the door open was only to keep the interior lights on while starting the car. When I first turned the key to ON for GP operation, I could see the interior lights dim slightly while the GPs were ON. The GP light on the dash went out but the GPs remain ON for up to about 10 seconds after the GP light goes out. I would hit the starter the instant I see the interior lights brighten back up when the GPs finally turned OFF. This helped starting in below zero F conditions because the GPs stayed hot long enough and lightened the load on the battery during cranking.
I thought about doing a mod to wire up a light to the GPs so that I have a "real" GP light to know for sure when the GPs are actually on or not. I never bothered with the mod because I stayed on top of maintenance and never had any cold start issues with the car during my 8 years and only 361k miles of ownership.
 

Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
IIRC, the GP light on the dash showed when the GPs were actually ON and you could hear the GP relay click on or off
Not intending to be picky here... just commenting for clarity.

I've a 2001 with the old-skool relay and I added an LED on my dash connected directly to the glow plug harness. I can confirm that the factory LED in the cluster is independent of the glowplugs actually having power... so more of a "OK to start" LED as well.

The other thing learned with my extra LED is that those pesky glow plugs run all the time, summer or winter, for up to a couple minutes *after* the engine starts. Emissions and driveabilty I'm told.. but it does help me understand why people get P0380 codes in the middle of Florida. :)

When they are in after-run mode they go out whenever the engine goes over 2500 RPM...which makes the relay click on and off as you run thru the gears.
 
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
This is reposted form another thread of mine. I am not just re posting, I just want to avoid much of the normal "my glow plugs don't work" suggestions that I have already tried. So a question abut the LED, did you just use a scotch connector or something on one of the harness wires? I think that could be incredibly helpful. I have LEDs in the cabin now, and its difficult for me to see the lights dim.

To recap, all the glow plugs have a resistance of 8.8 or 8.9. The harness seems to be alright considering I get a error code when I unplug any one of the glow plugs. By unplugging the CTS the ECU defaults to the fuel temp senor. When unplugging the FTS the ECU can read the CTS just fine, and both when plugged by itself are consistent with the other. When both are unplugged the ECU defaults to -4.5c. In either of these instances the glow plug light give .5 seconds. VCDS testing of the glow plug relay dims the cabin lights until the test has finished. I swapped out a different relay with no effect. The fuse is fine. No fault codes whatsoever. I did try to swap out the ECU with no effect but now I am wondering if it was alright. I did not do anything with the mobilizer so perhaps my test flawed. My gut says programming flaw, that for whatever reason the ECU programming is wrong, as demonstrated by its lack to default to -40 when the CTS is unplugged, and the fact that during output test it can turn on the GP relay but during regular use it cannot...tells me that it just does not want to even though the input factors such as coolant temp are functioning correctly.
 

Growler

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Joined
Nov 24, 2003
Location
Millersport, Ohio
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Schmutz, 2015 Golf Sportwagen DSG & Schnurren, 2001 Golf GL 2 door 5M
Are you getting voltage at the glow plug harness connections when the coolant temp sensor is unplugged? you will need a helper to cycle the key for you while you check each plug port on the harness.

and VCDS to clear the codes that this will throw.
 

firehawk618

Veteran Member
Joined
Aug 20, 2003
Location
Marysville, WA
TDI
2011 Golf TDI, 2dr, M6, Stock
Funny how the OP says they want to just hook up a manual switch and isn't interested in any more troubleshooting but every post is troubleshooting.

All you have to do is run a wire to your GP relay and either power or groudn that wire.

I will look when I get home and advise you which wire to tap and what to send to it.
 

csstevej

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Aug 12, 2004
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north nj
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2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Are you saying each GP is reading 8.9-8.9 ohms of resistance? It should only read about .8-1.5 or there abouts of resistance. That may be some of your problem.
 

Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
To run an LED on the dash that tells you when your glow plugs have power I tap into the glowplug harness in the cableway that runs behind the air filter.

Thin green wire in this picture:




Ignore the big red wires at the bottom of that picture... they are going to this:



Got tired of flaky harness connectors and am trying an experiment with spade lug connections.
 

JB05

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Oct 20, 2005
Location
Il.USA
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Golf,2005,anthracite blue
I too have a pilot light for the GP's and was surprised to find that they run practically year round, although the duration varies. Another thing worth mentioning is I have a scan gauge and the coolant temperature is always a few or more degrees warmer at cold start up than the outside temperaure, sometimes 10 degree difference.
 

dtvenus

New member
Joined
Sep 13, 2012
Location
Huddersfield, UK
TDI
Seat Leon
Wiring up heavy duty glow plug switch to replace relay

My issue was the glow plug relay switching on only when the engine started! No good for warm up and no good for the glow plugs. Fortunately I left the harness pulled off the new plugs I'd fitted and used Easy Start spray, until I decided to fit a manual switch after my nephew suggested this was an option.
Bought a heavy duty push switch which releases as soon as you let go ( good, because you don't want the plugs on after the engine starts). Along with 17 amp wire (should ideally be 35 I think, but the glow plug circuit is only switching on the 5 seconds needed to warm up the combustion chamber) and two 35 amp connectors. I'm in the UK and couldn't get the male blade connectors to slot in the 12 volt supply and exit to the plugs, where the relay plugs into the rail underneath the steering wheel ( My TDI is a Seat Leon). I bought flat round connectors designed for bolting to a threaded stem. I filed them at each side to get down to the same width as the heavy duty blades on the relay.
Drilled a hole for the switch in the plastic trim which completes the facia under the steering wheel. Jobs a gud'n as they say. The circuit is fused from the battery supply, so if the wiring I've put in managed to short out, it should blow the fuse. ( I tested all this would work by first pushing a connecting wire into the two slots where the relay fits, and taking a reading at the harness to plug connectors. I would advise to do the same first).
 
Last edited:

Alchemist

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Joined
Nov 3, 2007
Location
Lethbridge, Alberta
TDI
'04 ALH Golf
This should be what you are looking for. The ECU sends 5V from pin 9 to the glow plug control module (aka relay) via a blue/black wire, which connects to pin 10 the ST terminal. The control module sends 12V to the plugs as long as it is getting 5V from the ECU. All you need too do is put 5V on this line and the plugs will be on. The easiest way to get the 5V is with a regulator such as 78L05. Radio Shack probably has them for a reasonable price. It is a very small device and uses a simple hookup, just 12V in, ground and 5V out.

Paul
 
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
To answer a question above, I was able to test the resistance at each plug tonight along with the power supply to the harness. Each plug reads 6.9-7.0 ohms. I was sure to make sure the range was correct. I unplugged the CTS, which on my car it reads the fuel temp. when the CTS is out, so I then unplugged the pump harness to which the ECU then read -4.5c as the temp. Doing that, my multimeter jumped form .000V to .167v as soon as I turned the key on, and then back to .000v when I turned the key off. So it seems I am not getting voltage at the harness. Again, other than a CEL for unplugged glow plugs, no codes.
 

Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Hmmmm...something's going on with both your voltage and the resistance of the glow plugs, which should be in the 1 to 1.5 ohm range, plus whatever resistance your multimeter adds.

I suppose it's possible the multimeter's fuse is getting thin and weak... What resistance reading do you get when you simply short the leads of your multimeter together?
 

firehawk618

Veteran Member
Joined
Aug 20, 2003
Location
Marysville, WA
TDI
2011 Golf TDI, 2dr, M6, Stock
Hmmmm...something's going on with both your voltage and the resistance of the glow plugs, which should be in the 1 to 1.5 ohm range, plus whatever resistance your multimeter adds.

I suppose it's possible the multimeter's fuse is getting thin and weak... What resistance reading do you get when you simply short the leads of your multimeter together?
Yes your readings are way out of spec for your glow plugs. Do like Vince Waldon said, short your leads together, you should have 0.0 or damned close. Otherwise your meter is mafunctioning.
 

csstevej

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Aug 12, 2004
Location
north nj
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2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Do you have a spare GP you can try checking the ohms with? You can also try changing the battery in the meter and see what you get.
 

Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
You can also try changing the battery in the meter and see what you get.
Yup... good call... that could explain the high ohms reading as well.

It could also mess up the voltage readings... OP are you getting a normal 12.x V reading when you measure directly at the battery?
 

Thirstyturtle328

Veteran Member
Joined
Oct 15, 2011
Location
Eastern NC
TDI
2002 Golf GLS TDI
To run an LED on the dash that tells you when your glow plugs have power I tap into the glowplug harness in the cableway that runs behind the air filter.

Thin green wire in this picture:




Ignore the big red wires at the bottom of that picture... they are going to this:



Got tired of flaky harness connectors and am trying an experiment with spade lug connections.
How did you use those type connectors?
 
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
I was always able to get correct readings from the battery and fuses, 12.97V always. I checked the multimeter and discovered that perhaps one of the fuses was blown. I replaced it along wiht new batteries and took some readings on the plug resistance again. This time they all came in at .4 to .6 Ohms. Now as far as touching the two end together I did that. At first it reads 00.0, but if I wait a few seconds it will slowly move up to .6 Now sure what that means. I can account for this by saying that the fuse I used was slightly thicker than the one in there, so that may have bumped the overall resistance. It takes about 10 seconds to do that though, where as the GP readings were pretty quick. Anyway, I don't want to move too far off track here.
 
Last edited:
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
This should be what you are looking for. The ECU sends 5V from pin 9 to the glow plug control module (aka relay) via a blue/black wire, which connects to pin 10 the ST terminal. The control module sends 12V to the plugs as long as it is getting 5V from the ECU. All you need too do is put 5V on this line and the plugs will be on. The easiest way to get the 5V is with a regulator such as 78L05. Radio Shack probably has them for a reasonable price. It is a very small device and uses a simple hookup, just 12V in, ground and 5V out.

Paul
If my prediction is correct in that, either something is wrong with the ECU or some information that the ECU is getting is resulting in the 5V not being sent to the GP relay, my question is this: if I were to hook up a simply 5V line to the GP relay, and with that new 5V line the relay opens the 12V to the plugs, will this cause a CEL? I know that one of the things abuout these relays is that they actually provide information back to the ECU. So if the relay thinks it is getting 5V from the ECU (like it normally should) that also means that it will report information back to the ECU. So when the ECU gets this information will it freak out and put out a CEL?
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
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2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Are you getting 5v to pin 10?
 
Joined
Oct 4, 2010
Location
Columbus, OH
TDI
2003
Can someone tell me what the pin numbers all mean on the relay? The ones I don't know are ST, D1, and 31. The rest I get. I ran a wire from the battery to the 87 pin and was able to get 12.5V at each of the "G" pins, which is good. I also tested the harness connector and there was 12.5 volts on the wire that goes to pin 30 on the relay, so that is good. I think the relay is good. I tested the harness pin that connects to ST on the relay however, and did not pick up any voltage...that is bad. I think I need to test the pin on the ECU that sends the 5V. Will the ecu still send it if the whole connector is taken apart? I am starting to think that the best way may be to just send the 5V to the relay through a manual switch.
 
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