Glow Plug Harness Issue

Hey folks,
I have a 2004 Passat, BHW. I've had a check engine light on for the glow plugs (cylinder 4) for a while now. Hadn't sorted it out cause I had no trouble starting but I need it to pass inspection so I'm getting around to taking care of it.
Here's what I've done:
I replaced the glow plug itself. Cleared codes, it came back.
I tried to replace the harness but I couldn't find where it connected to in the car so I took it to a mechanic.
I suppose the mechanic couldn't find where it connected to either so they clipped the end off of the new one, clipped the plug connector off the old one, e taped the **** out of it and charge me $200 to do it.
I am planning on trying to get a refund for the ruined part and the work they did because I am livid.
But as far as actually fixing the problem, does anyone have any insight as to where the glow plug harness actually connects to? I haven't been able to find any advice specific to my engine on this one.

There's a huge "Glowplug 101" thread that's great reading, but in the meantime did the glowplug you replace actually test bad? They are numbered in reverse order, so you may have swapped out #1 instead.

Other point would be that it is in fact common practice to cut off the connector and splice the wires; the factory harness is well-taped and buried under the battery and air filter, and so lots of labour involved in tearing everything apart just to get the wires all the way back to the connector.

No reason why a splice is not a reliable connection... if done well, of course.

I did what Vince suggests. The new harness came with 8 feet of wire which is more than is needed. On my BEW, the GP harness connects to a smart relay under the cowl at the base of the windshield on the left side. It is visible through the vents.
I too have a P0674 DTC, and I thought the #4 glow plug was farthest from the TB.
A new glow plug and lots of Deoxit did not help. The CEL is intermittent by the way, which is driving me crazy. All GP's check out good.

Johnsontf,
For your future reference:
http://forums.tdiclub.com/showthread.php?t=130044

Okay, that is good to know about the install. I am glad I didn't go in there demanding a refund if that is the common practice. Seemed like a cheap fix when I found it.
I swapped out the closest plug to the cabin because thats the one I believed to be #4 based on research.
Does anyone have an idea on what is the next thing to check now that the glow plug and harness are both replaced to clear the check engine light?

Johnsontf said:

I swapped out the closest plug to the cabin

Click to expand...

Does it test bad, tho? Multimeter on ohms setting, should read around 1.

So I got myself a multi meter to check the plugs and I am getting some weird numbers. On the plug I removed I got .3 ohms.
In the 4 in the car I got 130, 130, 130, and 160 ohms. Though volts were 12.58 straight across. The voltage seems normal but based off what I've seen, ohms are way out of wack. Perhaps my meter is off? I have never used one before. I used the
I used the 101 thread and the following videos:
https://www.youtube.com/watch?v=4Po_1pNHE1Y&t=186s
https://www.youtube.com/watch?v=Siy6jgTAHxg
Thanks guys very much for your advice, I really appreciate it.

Typical reading on a good plug is 0.5-0.7.
Here’s that big glow plug thread that will explain everything.
http://forums.tdiclub.com/showthread.php?t=79819

Folks,

I installed a Powerstroke 6.0 glow plug harness on my Audi TT -> TDI (ALH). It was cheaper and fits perfect. It's a four wire harness. Here's a link on using the Powerstroke harness:

http://www.forums.tdiclub.com/showthread.php?t=453767

Eric