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

How to read (or print) long topics easier/quicker

It does take way too long for folks to read or browse through so many pages of
this thread. But here's what I suggest, that does save a lot of time --

Click on "Thread Tools", which is within the right half portion of the header
that's just above the main post reading area (frame) ... it should expand into
a drop-down list of commands. Look for "Show Printable Version", and click
that;

Once your browser shows the "Printable Version" of the long thread (which is
great for reading, printing, searching, etc. and renders so much more quickly,
but doesn't have some personality features such as user icons, reply buttons,
etc.), look at the upper-right corner, where there is a list of pages, and see that
there's a link that says "Show 100 posts from this thread on one page". Click that;

Now this entire thread to date is about 4 pages in your browser, and is more
quickly readable (and printable). Larry

I have been thinking of glow plugs lately and I need to get some feed back on my thoughts.

I was helping a lady with her 2000 Golf. It showed a GLow Plug fault. An ohm check showed three glow plugs with a dead short. The odd part is that this CEL came on suddenly. She had gone through some water, but I'm not sure of the details on that part.

The 2000 has a two wire glow plug circuit (I'll call them circuit A and circuit B). As I understand it, the computer reads the load on each circuit and when there is a certain amount of difference between the two, the computer says, "WHOA" and throws a code.

So why did she suddenly get a code with three bad glow plugs? I have a hard time believing that three GPs would fail at the same time so I have been pondering this and this is what I have came up with.

A GP failed in Circuit B and threw a code. Before she got to someone to clear the code, one GP in Circuit A failed. Someone cleared the code, but the computer was happy because it saw the same load on each circuit.

Then the other GP failed in circuit B and now the computer sees a different load between the circuits and it throws another code.

I just don't like the three failing at once, so this would explain it, but am I right or even close?

Three have a dead short - that is, 0 ohms? Or am I misreading that - gps usually go high in ohms as they go out.

How many miles on the car?

whitedog, I thought that the one plug out of four that showed relatively
high resistance would be the problem plug. I believe that the vehicle
assumes that the GP is a near-short (very low resistance) and measures
the drop across a known load, for each half of the four GPs. Larry

RD, we had zero (0) ohms on three (3) GPs and 1.4x (one-point-four-exs) on the other. I checked everything on my tester that I could think of to confirm I was doing this correctly because that didn't look right to me either.

She has four new GPs coming and I will check everything then again, but welcome any advice on what I could have done wrong.

whitedog said:

RD, we had zero (0) ohms on three (3) GPs and 1.4x (one-point-four-exs) on the other. I checked everything on my tester that I could think of to confirm I was doing this correctly because that didn't look right to me either.

Click to expand...

Are you CERTAIN that the "1.4x" on the display does not mean infinty? (open)

I beleive the ONE GP with high impedance will be the bad one.

If your meter is reading "0" ohms on the good GPs, then your meter is not sensitive enough to measure less than one ohm accurately. In that case, assume the "0" ohm readings to be the GOOD glowplugs. What range were you using?

Question: What does your meter display when the probes are not touching ANYTHING? (I am wiiling to bet it is the infinity reading of 1.4x you were seeing.)

This is the meter I use ( http://www.metrictest.com/catalog/pdfs/product_pdfs/flu_85-3.pdf )

DISCLAIMER: I am a trained electronic technition with over 25 years experience

When not touching, each other or anything, the DVOM was reading OFL. Touch the leads together and it would read 0 ohms. It does auto range, so it picks the best range for the reading.

I'm with Bruce on this. If its reading 0, that is not infinate. When I touch my leads together, they read a resistance of .6 ohms. So the fact yours reads 0 when touched together and on 3 of the glow plugs would lead me to beleive that it is reading a resistance, but becasue its lower than 1 ohm, it cannot register an accurate value. That seems to me that 3 of them are good and one has a high resistance. A bad glow plug does not necessarily have an infinate resistance, it can also have a high resistance. Have you used this multimeter on any other glow plugs?

I have not used it on other GPs. I have some in the garage that I will try tomorrow. Thanks.

Test the bug (is it running?) with the same meter. Perhaps it time to change the battery (in the ohm meter)?

I checked my GPs today with two different Meters and got two different numbers. I'm going to do what Kern suggested and bring them both home and see what they both read on the Beetle.

Thanks to everyone for helping me.

I have found that most DVOM (digital volt/ohm meter) discrepancies are attributable to the test leads.

D'oh! forgot somethig when I left work, didn't I?

D'oh! forgot somethig when I left work, didn't I?

So we have to wait another day. The suspense is killing me!

Am I correct in assuming that, on a 2000 Jetta, I can simply cut-and-crimp to REPLACE a harness, as is detailed in the pictures, without having to try to unplug it the hard way?

rdkern said:

So we have to wait another day. The suspense is killing me!

Click to expand...

Or two...

Is anybody out there today that can help this beginner? I'm afraid I'm in trouble.

I have followed your Glow Plug testing, and wanted to know if there is a way to test the Glow Plug Relay itself.

I have replaced my Harness, the OEM glow plugs tested fine, but today unplugged the Coolant Sensor, and cannot get any readings from the harness at all.

blacksheep said:

I have followed your Glow Plug testing, and wanted to know if there is a way to test the Glow Plug Relay itself.

I have replaced my Harness, the OEM glow plugs tested fine, but today unplugged the Coolant Sensor, and cannot get any readings from the harness at all.

Click to expand...

If you unplugged the coolant temp sensor, you have about 15-20 seconds to test for power at the harness after turning on the ignition. If you do not have 12v at any of the harness terminals after turning on the ignition, then you likely have a bad relay. It is not common, but I have seen 2 bad relays in my years of diagnosing GP problems, so it does happen. Simply changing the relay worked in both cases.

Thanks to those who put this thread together. My volt/ohm-meter tests allowed me to eliminate the plugs and the relay.

A combination of using a water/baking soda solution for removing harness contact corrosion, compressed air to dry, using Lectromotive contact cleaner, and more compressed air to dry, I was able to resolve a P0380 code.

RE: my earlier post.

I have the car at my house right now and I checked the (cold) resistance of the GPs with a different DVOM while installed in the engine. All were at .9 OHMs.

I then pulled all of the plugs and tested them again.

All were at .9-1.0 OHMs.

Hmmm...

So Installed the plugs in the harness, (but not in the head) Unplugged the temp sensor and turn the key on. One GP didn't get at as red as the others so I moved it to a different position with the same result: that same GP didn't get as red.

I put everything back together, cleared all codes and took it for a drive. So far no code. I will start it tomorrow morning and see how it does, but I'm just not sure how to proceed. It has a new harness installed, so I'm also reticent to say that is the problem.

I understand the voltage drop test theory, but I am very shakey on the best way to actually do it. Can I do a Voltage drop test on just the GPs and if so, how would you do that, specifically?

I have the car the rest of the weekend, so I have some time to fiddle around.

I have four new GPs, but I'm reticent to swap them in.

That sounds interesting whitedog -- when you activate the GPs while they're in the
harness but out of their positions in the head, how do you connect the ground (the head)
to the threaded portion of each GP to complete the circuit? An alligator clip or clamp or ??
Sorry if I missed that info in an earlier post above. Larry

Larry, I used jumper cables clamped to the threaded portion of the base for the ground. If I had another set of cables, I could have glowed all four at once.

What I did for a "voltage drop test" was I removed the GPs and hooked the jumper cables to the battery, then the ground onto the base with a multimeter lead clamped in there. I then clamped the other MM lead to the other clamp, then I touched that lead to the top of the GP. The voltage quickly went from about 11.45 VDC up to about 11.57 VDC, then it slowly climbed to 11.71 VDC. It was the same on all four GPs, so I reinstalled the old plugs. I hit them with Deoxit and a Qtip, then I stuffed a 1/4 In square piece of Aluminum foil in there. No code right now, but I still wasn't happy with it.

I pulled the panel under the dash and checked the GP relay. Well, as much a sicould check it. Nothing was obvious on the outside, but I did find a wire that was spliced into the Pin 31 terminal and it ran "Somewhere". I didn't trace it out.

So, at this point, I'm a looser on GP 101 and would appreciate any feedback on the things I have done so far.

Woof

mystery

Whitedog, the main thing that would have me concerned is the somewhat intermittent nature of the
spring-clip GP harness connection onto the GP tips -- if the readings look good while you have your
test setup in place, then later in order to re-mount the glow plugs you'd have to remove the harness
connection and re-insert as a last step. I wish those push-on GP harness connectors were more reliable
over time. I hope that the aluminum foil makes a difference on this one!

The other thing I'd like to know (since I am a novice) is about that pin 31 spliced-in wire. Good luck; Larry

WD - you're just chasing a light, right? I think you fixed it.

Probably gp harness - since all the gp's test out. However, I'd probably replace them, since all the effort has been expended, might as well return the car with gps that shouldn't be a problem for 100K/10yrs.

I also don't like one glowing less than the others - reason #2 to change.

I'd be surprised if you don't have this one fixed.

rdkern said:

WD - you're just chasing a light, right? I think you fixed it.

Probably gp harness - since all the gp's test out. However, I'd probably replace them, since all the effort has been expended, might as well return the car with gps that shouldn't be a problem for 100K/10yrs.

I also don't like one glowing less than the others - reason #2 to change.

I'd be surprised if you don't have this one fixed.

Click to expand...

If the GP light comes back, we are going to change them.

my golf recently threw the 17058 code and i'm looking to go through this procedure. bare with me because i'm extremely new at doing my own work on a vehicle, but i can't seem to get my newly purchased multi-meter to work on testing the plugs. am i missing something...does the ignition need to be on to test them??

The (digital) multimeter test is only a rough guide, and not foolproof by any means...

Make sure you're using a very low range for Ohms (200 or less), remove the glow plug harness, find a good ground point for one of the test leads, and check the resistance of each glow plug... it's a bit tight in there, and you may need to rotate the harness to get it out of the way... You should get readings in the range of 0.8 to 1.3 ohms for each... If you find one that gives you Infinity or Zero (or something like 280 ohms), then you've found an obviously dead glow plug... If not... the problem's most likely corrosion inside the harness... In your car, Glow Plug # 4 is probably on Cylinder # 1 - towards the passenger side... some cleaning inside the contact area of the harness will help... DeOxit D5 is very helpful here - and you may need several applications...

All the best,

Yuri.

I am getting the "17056 / P0672 (Cylinder 2 Glow plug circuit (Q11))" code. Can I assume my problem will be solved by replacing the glowplug in just this one cylinder? I checked the resistance and it seemed to be in line with the others. Also, there seems to be some confusion over which cyl. is actually "Cylinder 2." Which cylinder is that when I'm facing the engine?