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

So...reading all through this and have a few questions.

2000 Jetta 5spd, 228k, original injectors

Just this winter I've been having long, hard starts. It's always started quickly with 1 glow no matter how cold. Now it's multiple glows, and "chugging" lots of smoke and riding the starter to get it to catch.

I put new glowplugs in 3 years ago as I got a check engine light about them.

Here's what I've done.

battery is excellent, 2yrs old plant of power DEKA
Glowplugs,BERU, 3 yrs old, all test at .6 ~ .9 ohms
Harness, testing shows like 16.88 then drops when you hear the relay click off, my multimeter is a Klein and auto-sensing. All 4 exhibit same behavior.

It's due for a timing belt basically within the next few thousand miles.

Once it stops chugging, could be 5 seconds, could be 10~15, it catches and idles normally but smokes for a minute. This was 25 degrees this morning.

I don't have a Ross Tech cable anymore. There are no check engine lights other than the ones I forced by unplugging the CTS and Glowplug cable to check. I need to reset those.

Could this be injectors? Timing drift?

EDIT:
Forgot to mention: Right after startup when it's running smooth, as I drive away, I get a clicking from the drivers side (relay sound) and the car slightly hesitates skips for that split second. It does this every 2ish seconds for about a minute or 2 or it gets warm.
Relay 109? Could that be causing weird issues on starting?
thanks

Alright here's my dilemma. My glow plugs are all good. I've replaced my glow plug relay. The fuses all check out. My harness isn't getting power im getting .26 volts 1-4. The glow plug light always comes on for 2 seconds then shuts off. The car starts rough in the cold. The cel comes on within a minute of it starting. Anymore tests I can do. Can I jump the relay to force power to the harness. If so which pins? Any direction would be appreciated. The car is a 2000 golf tdi manual btw.

wjfyfe said:

OK, if this has been already addressed I apologize for missing it. We get the error code 16764. I have done all of the checks listed at the beginning of this thread at least three different times and have found no abnormalities, I have replaced the harness and we still get the error code. Sometimes the glow plug light takes a few seconds to go out, (OAT above 40 degrees), and that is a for sure tripper. Sometimes the CEL does not come on until a few miles down the road. If we turn on the ignition, wait a minute or so, turn off the ignition then turn it on again, wait for a few seconds more before actually starting the engine the CEL usually will not show.

Any further thoughts or ideas? Bad Coolant Temperature Sensor maybe?

Thanks,

Bill

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Well, we finally just got tired of looking at that CEL and took the car into the shop in which it was diagnosed with a bad coolant temperature sensor..............

Bill

wjfyfe said:

Well, we finally just got tired of looking at that CEL and took the car into the shop in which it was diagnosed with a bad coolant temperature sensor..............

Bill

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Interesting, that shouldn't involve the CTS.
Did you use an OBDII device (VCDS or equal) to successfully clear the code?
For some strange reason GP faults don't go away on their own.

I just went back to our book showing error codes and...............oops, (a big OOPS), on my part. The first time years ago we got the code 16764, (glow plug heater circuit), which was correct for we found a bad glow plug. Shortly after that the CEL returned with 17664, (see where I made my error?), and I have been chasing the wrong problem all of this time.....................

(17664 = Engine Coolant Temp)

Bill

Quick Question should there be continuilty between the two wire glow plug harness.

I have read one wire for two glugs other wire for other two plugs.

I don't think so. Each should be a power sourse that can be independently monitored (gp lights) so I wouldn't think so. I didn't go through the wiring diagrams though. What do you find?

CLTMXTDI said:

Quick Question should there be continuilty between the two wire glow plug harness.

I have read one wire for two glugs other wire for other two plugs.

Click to expand...

That's correct, and it's connected to ground so there would be continuity on the motor side, control side don't know.

CLTMXTDI said:

Quick Question should there be continuilty between the two wire glow plug harness.

I have read one wire for two glugs other wire for other two plugs.

Click to expand...

OK here is the deal from relay 180 there are two power connections going to the two wires on the harness. my harness has continuity between the two wires so with either wire i have continuity at all four glow plugs. if this in normal is the question could some one check there harness and see. The relay will power both wires coming from it with 12volts. The only reason i can think of for this is for amperage. Before purchasing a harness or making a new one I need to know if it is meant to be that way. or do i make a harness where i send one power lead to two plugs and other power lead to the other two.

OK found a post from wing nut he said two for one. I have a bad Harness made my own works great.

"It does not matter which wire attaches to which wire. Both wires simply feed 12v to the plugs....2 plugs for each wire". The other end of the plug (meaning Glow Plug) is grounded to the block."

ShopDap.com where I get all my tdi items !!

ok so I had a cylinder 3 sensor code, I replaced the glow plug 3 in cylinder 3 and was good! then a few months went by I got the same code on cal 3. So I checked all the plugs .5 ohms on all 4, I switched cyl 3 with cyl 1 glow plug, now I have cyl 1 sensor code? I don't understand why I have the ohm range on all 4 plugs equal but getting code on that same glow plug ?? any ideas

Replacement was a different unit?
What model TDI?

Sometimes they show the proper resistance when cold but don't heat up in the same manner as when new...

Yuri

My car started rather hard this winter and I've been slow to get around to trouble-shooting the issue.

Using a 6 V 10 amp battery charger, each glow plug warms up to a red glow after about 5-6 seconds. I have the NGK 7 V glow plugs - the BEW recall plugs.

Thinking maybe I had an issue with the glow plug control module, the "C" version, I bought a 75 mV 50 amp shunt resistor on eBay for $6 delivered. I used my Fluke 87 true RMS meter and tested it this morning.

Parked overnight the coolant temp still read about 22 deg C, whereas my car had frost on it so the overnight temp dropped to about 0 deg C. So could be my coolant sensor is off, but the temp gauge does read correctly at 190 deg F after warm-up.

Group 12 in VCDS showed a pre-glow period of 2.46 seconds and I did measure up near 70 mV, near the full 50 amps, for those 2.46 seconds. So I am getting the proper glow plug current. The post glow period was a long time after I started the car, a minute or more. Was reading around 17 amps during the post glow duration.

The Torsion value is -0.5 as the timing belt has some miles on it. Might be I just need to crank that up to +1.0. I'm going to change the belt this fall.

I'll keep an eye on the coolant sensor also next fall to see if it seems legit. But from what I can gather this morning, the glow plug circuit itself is working okay.

Hello everyone, I'm new here and I thought I'd find a "Members page" where I could say "Hi" to everyone but I guess this works.

For the past several months my car has thrown an engine check light. I took it by autozone and they said it's the glow plugs. Got it. Replace them and the problem is still there.

Steps that I have taken to fix the issue:
- Replaced the glow plugs (3 times)
- Replaced the glow plug relay
- 0.8 ohms = on the glow plugs
- 0.249 VDC = for all 4 glow plug terminals
- 12.39 VDC = glow plug fuse

So I watched a video on how to replace the glow plug harness and it seemed really simple so I gave it a shot. It turns out my glow plug harness is completely different. Traditional glow plug harness has 4 pins. Mine has 10...

Wiring harness connection:

New Glow plug harness:

Glow plug harness connector:

What my car looks like:

I have a 1999 Golf TDI ALH
195XXX miles

You simply cut the wire near the engine and connect the 2 wires to the 4 wires on the new harness. If you like to save money, these harnesses can be re-built with less costly parts.
Those links you posted are on your local hard drive.
I recently replaced my harness, all I found for sale was the "short" harness requiring cut and connect. I wish I had just re-built.

Ok I updated the pictures so that you can see them this time.

I used this youtube video.
https://www.youtube.com/watch?v=NRLgcz0r2ec

My glow plug harness doesn't even look the same.

The harness on the right, with the 2 big wires, is your glow plug harness, not the 10 wire harness.

Vince Waldon said:

The harness on the right, with the 2 big wires, is your glow plug harness, not the 10 wire harness.

Click to expand...

Amazing...I'll start working on it today. Thank you!

So I disconnected the plug and this is what I see.

[/URL]

The glowplug harness that I have now, I know it's the correct one...so why is this one so different?

Thank you so much for this thread! The step by step really helped me be willing to get into my diesel for the first time.

• 2001 Jetta TDI Manual
• P0380 code at every start (even after clearing)
• replaced all glowplugs with original spec Bosh parts
• cleaned harness with D5
• checked fuses on top of battery
• pulled temp sensor (thanks for the MAF practice tip!)
• all 4 GP connectors on pulled harness measured 9.6v for the 20 second or so window after turning the key
• battery alone measures 12.2v on the same multimeter settings

Question: Should I be looking at replacing the harness or the relay? I read through the thread and am not sure.
Thanks in advance!

MrAsano said:

So I disconnected the plug and this is what I see.

[/URL]
The glowplug harness that I have now, I know it's the correct one...so why is this one so different?

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Early TDIs had the glow plugs wired in pairs... so only two wires in the main harness. Later ones had wires to each glow plug individually...so that each glowplug could be monitored for faults.

Your Golf is the 2-wire variety, and the replacement harness you bought is the 4 wire variety... NOT technically the "correct" one for your car.. although you can cut and splice it to work.

Vince Waldon said:

Early TDIs had the glow plugs wired in pairs... so only two wires in the main harness. Later ones had wires to each glow plug individually...so that each glowplug could be monitored for faults.
Your Golf is the 2-wire variety, and the replacement harness you bought is the 4 wire variety... NOT technically the "correct" one for your car.. although you can cut and splice it to work.

Click to expand...

Thank you so much! Now I just need to find a new old model harness or find a write-up on how to do it.

sharpfork said:

Thank you so much for this thread! The step by step really helped me be willing to get into my diesel for the first time.

• 2001 Jetta TDI Manual
• P0380 code at every start (even after clearing)
• replaced all glowplugs with original spec Bosh parts
• cleaned harness with D5
• checked fuses on top of battery
• pulled temp sensor (thanks for the MAF practice tip!)
• all 4 GP connectors on pulled harness measured 9.6v for the 20 second or so window after turning the key
• battery alone measures 12.2v on the same multimeter settings

Question: Should I be looking at replacing the harness or the relay? I read through the thread and am not sure.
Thanks in advance!

Click to expand...

images for reference:

Sharpfork- All seems well, did you try clearing the code?

BobnOH said:

Sharpfork- All seems well, did you try clearing the code?

Click to expand...

Thanks BobnOH, I'm stuck!
I did clear the codes with my bluetooth OBDII thing. I can see in my torque android app that the P0380 code becomes pending pretty quickly after clearing the code but doesn't show until subsequent restart. I'll try it a couple more times to be sure.

Are you saying that 9.6V is OK at the harness? I thought it was supposed to be 12v.
The car runs fine but I need to pass an emissions test and a check engine light is an automatic fail.

I've replaced two glow plugs on my ALH. Then I got the bright idea of "hey! I live in hot Texas. I don't need a glow plug." I found that disconnecting the main power cable will not trigger any codes and the glow plugs cannot work so they don't burn out. I simply unscrewed the connection on top next to the battery and bend it around so nothing touches it. Works great. One other point, This last winter I drove to visit family in Northern California. I found myself spending the night in Ely, Nevada (6400 ft. above sea level). It was 22°F in the morning. The car started--a little reluctantly but it started. Afterword I was in McArthur, California at a bit over 3000 feet. The car sat for 4 days. The early morning temp was 15°F. Again it started--reluctantly but it started.

JohnWilder said:

I found that disconnecting the main power cable will not trigger any codes

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The cable to the GP harness or something else?

JohnWilder said:

I found that disconnecting the main power cable will not trigger any codes and the glow plugs cannot work so they don't burn out.

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Hmmm... I am really surprised to hear that this worked.

The glow plug system is tested every time the car is started, and the glowplugs run for several minutes after the car is started, rain or shine, summer or winter, regardless of if they were used to start the car in the first place.

Good that it worked for you... dunno why though.

sharpfork said:

The cable to the GP harness or something else?

Click to expand...

Somewhere in this thread I think I posted a "magic" fix that I have used...

Sometimes it's just the connection right at the ends of the connectors that are problematic: I suppose that one could squeeze down to make them tighter, but one risks breaking something (the insulation can be brittle and fall apart, or, the metal connector might break or collapse). This "fix" is only good in instances in which: 1) GPs check good; 2) Voltage shows up at each connector correctly; and, of course, 3) The system still balks (throws a code). I stuffed some aluminum foil over the GP connector and then shoved the harness connector on and... FIXED! Did this on the son's car (which, after cleaning with DEOXIT and applying dialectic grease was still popping a GP code) many months ago and haven't had a GP code thrown since.