'02 Jetta ALH Glow Plugs Not Getting Power

Hi Everyone, i wanted to test to see if my glow plugs were getting power today and here's what I found. I ohmed all the glow plugs and they were all good. Before I go on, i want to mention that my glow plug light only comes on for one second when i turn the key on and then goes out. I hooked a test light between the glow plug harness and ground and turned the key on and got nothing. I then unplugged the coolant temp sensor (which supposedly forces the glow plugs to get power for twenty seconds) and turned the key on again and still got no power to the glow plug harness. i checked the fuses on top of the battery and they are fine. Where do I go from here? Is my coolant sensor bad? Is the glow plug relay bad? What number is my glow plug relay? Any help is much appreciated. Thanks a lot

Update: I've located the glow plug relay under the rain tray thing under the driver's side wiper blade and removed it. I want to ohm out the coil to make sure its good and also put 12V to the coil to make sure it pulls the contacts in but there is no diagram on the relay and I don't know which two pins go to the coil. Anyone able to help me? Thanks in advance

What is the problem you are trying to solve? Is there a code being set? You say the GP light goes out after 1 second.

John

The car is starting hard and I want to make sure the glow plugs are working. I've got power to the glow plug relay but no power at the glow plug harness. I want to ohm out the coil in the glow plug relay and possibly put 12v to it to see if the coil pulls in.

Glow plug testing

The procedure you used to get voltage at your glow plugs will not work with a 2002 to 2003 model. My Bentley manual says they used a Glow Period Control Module for these two model years and suggested using a current clamp type meter as the only way to test. I suppose you will have to wait until the temp. drops to 9 degrees to be sure or use a can of Air Duster inverted to cool the water temp. sensor.

Lack of working glow plugs in an ALH TDI could not possibly impact the starting in July in Michigan. Your glow plugs may indeed not be working, but something else is the problem causing the hard starting.

According to the Bentley Wiring Schematic for the 1.9 2001 & 2002 models, the GP Relay is located on the relay panel (postion 10). Well, as you have discovered, that is not correct. The GP Relay is much larger and will not plug into any receptical there.

The diagram is as follows (hope I can make it understandable): Connection points are numbered. The numbers to the left are by me for reference.

1. -11/30 goes to the battery (6.0 size red wire)
2. -6/87 goes to an "in the wiring harness" multi-splice (involving several components) that are all tied together and receive power from fuse #34 (engine control elements). (1.0 size yellow and black.
3. -7/31 goes to a common ground (0.5 size wire, brown and red)
4. -1/G1, 2/G2, 3/G3, & 4/G4 go to their respective GP
5. -10/ST goes to pin T121/9 on the ECU (0.35 size wire, blue and black)
6. -9/D1 goes to pin T121/33 on the ECU (0.35 size wire, green and black)

I suspect connections 5 & 6 that go to the ECU provide the input info for the GP Relay to be activated!

Number 2 above may provide the current for the coil when it is activated by the ECU. The number 1 wire listed above obviously provides current to the 4 GPs.

Hope this helps!

Although called a relay, it is in fact an electronic control module. The ST pin on the module is an input from the ECU. The ECU sends a series of 5V pulses to the controller which in turn sends 12V pulses to the plugs. The length and time between pulses causes the average output to vary so the glow plug temperature can be controlled according to engine needs. There is no simple test for this module as there would be for a conventional relay.

same in my 01 jetta considering it has been below freezing and the gp light is only on for a very brief moment.. however i didnt test anything.. but this is typically a relay problem?

I have the same symptom. Code for #2 Glow Plug. Found a loose connection at #3 from timing belt. My Glow Plugs have 20K miles & are Bosch. All plugs are withing .2 ohms. All fuses test ok. Did not do an amperage clamp test. I'm now waiting for the three cycles for the ECU to throw another code. On my car, 2003 Golf from Brazil, the glow plug brain is next to the main brain behind the wipers. One thing I did find, but should not have any effect on the current problem, is the main metallic fuse on top of the battery is 110 amp not the 150 amp for the 120 amp alternator.
Lets keep this thread running & post our solutions.

Hehe, you guys are wasting your time. Glow plugs are ONLY necessary in these engines when the temps are quite cold(below 20*F). Otherwise, you do not need them and they are just used for emission purposes.

The light ONLY stays on when its really cold.

Relay failures are non existent on these cars. Stop chasing a problem that is not a problem in the first place.

I believe my Bentley manual says 48F (9C)

Quote from the Bentley: "In addition to pre-glowing, the glow plugs will continue to operate after the engine is started. This is known as afterglowing or extended glow period and is used to reduce engine noise, improve idle quality and reduce hydrocarbon emmissions! The afterglow function is enabled after every start, both hot and cold, regardless of whether or not preglowing has occurred, until the specified time has expired or the engine speed exceeds 2500 RPMs. Both the TDI and the PD TDI function in the same way with the same operating parameters."

The Old MK1 Diesel's GPs would continue to glow after start for a specified period of time .......very obvious if you had a Volt meter and watched it closely at engine idle....volt jump up when the GP Relay kicked-out!

Right, AndyBees. Afterglow has NOTHING to do with the starting process - by definition. It only occurs after the engine has started. Maybe it smooths out the running a bit, but it has nothing to do with getting the engine started.

Preglow is only strictly NECESSARY to get the engine running when it's really quite cold, and a significant aid when it's decidedly cool. Just like turbocharged798 said, actually. Except it's 50*F or so (48 if you like), not 20*F. But between, oh, say 35-50, the effect is not all that decisive. They just lower the cranking time and remove a little bit of strictly minor drama.

Quite a few of us have made starts down to freezing without waiting for the pre-glow, just to see what would happen. At 50, there is no discernable difference; none, zilch, nada. At 40, it saves cranking time and eliminates a brief period of rough running. By 30, you really miss them. But in the summer? Bah.

I went out and unhook all the glow plugs on my ALH in 20*F and it fired right up after sitting all night. A bit rough and smokey, but it started unaided nevertheless.

Diagnosing apparent GP issues

I think we all understand that the disesel engine is a compression fire engine! Although I live in southeast Kentucky, occassionally we see temps near zero and below. I've started high mileage worn out 1.6 engines with a good GP system and battery when I thought it was impossible due to temps near zero Fahrenheit. Of course, we know the lower the engine compression, the less likely it will start at a given temp without the aid of a GP system that's functioning properly!

So, did you guys read the initial post to this Thread? The dude apparently thinks he has issues with the GP system. He has been testing it, and apparently come to the conclusion something is not working properly........ He lives in Michigan and the temps there will soon be well below the engine's ability to start on just COMPRESSION alone.

The Bentley info that I provided was for the OP's benefit as to how the GP system is designed to work. Sure, there may be other issues causing the hard starting problem he described. He started with the GP system and seems to have discovered that a problem exists and was trying to trouble shoot it. If the temps were below the threshold of the specs, then he should have been getting 12 volts at the GPs. The last time I looked at the calendar, it is October in Michigan!

I have a ONE Cylinder DIESEL Polaris ATV that does not have a Glow Plug. It will start down to about 25 degrees strictly on compression .......any colder, I don't attempt to start it!....wastes battery and starter! Of course, I could ether it or use the heat from a hair dryer into the intake to bring it to life.

On extremely cold mornings, I've seen guys on coal mine sites start older model CAT engines by removing the air filter assembly and holding a burning brown paper bag at the inlet as someone cranked over the engine........worked!

Alchemist said:

Although called a relay, it is in fact an electronic control module. The ST pin on the module is an input from the ECU. The ECU sends a series of 5V pulses to the controller which in turn sends 12V pulses to the plugs. The length and time between pulses causes the average output to vary so the glow plug temperature can be controlled according to engine needs. There is no simple test for this module as there would be for a conventional relay.

Click to expand...

I've been doing a little research to try to figure out why pre-glow isn't working on my car. It's a gas-TDI conversion so there's a chance that something is wired incorrectly or maybe just shorted out.

In case anyone cares, I've got a pretty good feeling that the glow plug control module (J370) contains an L9524C glow plug controller chip:

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00134658.pdf

If you look at the wiring diagrams on page 24, it looks very similar to the 2003 ALH wiring diagram, including identically named pins 87 (+12V from relay 109), 31 (Ground), 30 (+12V from the battery), and G1-G4 (glow plugs). There are Control and Diagnosis pins that correspond to the ST and D1 wires coming from the ECU.

Greg

Based on above writing, a conclusion is that you don't need glow plugs assistance in starting as long as temperature is above 40 degres F. So testing for current and current not coming above this temperature number is moot and the conclusion that glow plugs do not work is incorrect per Andybees.

Finishing up a conversion where I installed a 2002 tdi into a 2001 2.0 gasser wagon. I’m in SoCal so obviously no cold weather. Not getting power to glow plugs or fuel lift pump...for the moment I just want this thing to turn over. So from what I am reading above...I should save the glow plug issue for a later date...because it should start just fine without them?

And just focus on the other issues?

Rnewcomb32 said:

Finishing up a conversion where I installed a 2002 tdi into a 2001 2.0 gasser wagon. I’m in SoCal so obviously no cold weather. Not getting power to glow plugs or fuel lift pump...for the moment I just want this thing to turn over. So from what I am reading above...I should save the glow plug issue for a later date...because it should start just fine without them?
And just focus on the other issues?

Click to expand...

One of our cars is a 2001 wagon with a 2003 ALH engine installed by the PO. The glow plugs weren't getting power because pin 88 of the ECU was not connected to 12V. Only took me 2 years to figure out! More details here:

http://forums.tdiclub.com/showpost.php?p=4112940&postcount=50

So in saying that I assume you mean that you were driving the cars for two years before you solved the glow plug question.

Yes, the glow plugs didn't work for the first 3 winters I owned the car (thought it was 2 years but just checked and it was 3.5 years!) The glow plug light would flash for only half a second when starting the car no matter how cold it was - even if the coolant temperature sensor was disconnected. Installed a Frost Heater to work around the issue. Correctly wiring pin 88 of the ECU fixed it and it's been fine ever since (5 years).

Also fixed a battery drain issue that was occurring for the first 1.5 years I owned the car that was caused by one of the circuits being wired to constant power instead of the output of Relay 109.

Check your wiring carefully and hopefully you won't have any issues with your conversion.

Does anyone know when the glow plug light does not illuminate when it should on the dash what does this mean? 2003 ALH,

Does the car start and run normally? If so, the usual approach would be to scan the car for codes with a VW-specific scanner and go from there, particularly if the CEL is on as well.

If the car does not start... a "no glowplug light" is the classic sign of a Relay 109 failure, or possibly the ECU fuse.

grahamtdi said:

Does anyone know when the glow plug light does not illuminate when it should on the dash what does this mean? 2003 ALH,

Click to expand...

Bad or disconnected 109 relay

If the light is not illuminating and the car won’t start, it just cranks and cranks then change this relay.

https://www.idparts.com/relay-109-a4b4a3-p-350.html

If on the other hand the glow plug light comes on and goes out but the car starts hard you probably have other issues.

Two excellent threads.

http://forums.tdiclub.com/showthread.php?t=79819

http://forums.tdiclub.com/showthread.php?t=199398