Glow plug mystery to end all glow plug mysteries

Ok, here's the short story:

Glow plugs don't work. It was about 39 degrees in N. Texas today. The car sat outside for 2 days and BARELY came to life after lots of cranking. I tried all the suggestions on this site, but I can't seem to get voltage to the harness.

Long story:

It's a 1999 Jetta, MK IV. The check engine light came on at 40K mi., when I lived in So. Cal. I determined the code was for the glow plug circuit. I didn't bother with a fix because I didn't need glow plugs in the warm climate. 80K mi. have since passed (w/ check engine light on). N. Texas gets cold now and then, so I need to get this fixed.

I've searched high and low on this forum for a fix, including the latest glow plug 101 thread--to no avail. I have replaced the harness and the relay. Haven't done the plugs yet, but one has infinite resistance, so I'll replace all if need be. I have also checked the fuse under the cover on the top of the battery for power. When I unplug the coolant temp sensor and check for voltage at the harness, I get nothing. Even despite a new relay and functional harness? Would one faulty plug cause the whole system to fail?

I'm about ready to install a manual switch to bypass the whole damn circuit, but I'm hoping something simple is happening. Thoughts? All I want is for the plugs to work. I don't care about the check engine light in particular. PLEASE HELP!

Have you replaced the 109 relay? Mine would crank forever to start until I replaced the relay. Starts instantly now.

Yes, thanks. Replaced 109 long ago. That's a whole other story

So you are getting no power the the glow plugs? Are you getting any power to the relay?

Did you know that with the CEL on all the time due to the glow plugs, you would not know if another fault developed and that fault could cause some expensive damage without any other warning?

How do you test the relay? Odds of 2 being bad? Has to be near zero.

I have rechecked the codes once or twice and they're the same. To play devil's advocate, problems like these won't eat up my precious time if there wasn't a $!#! computer to begin with. I personally favor the old days of NO COMPUTERS in cars like this, especially diesels. What's to go wrong? If it don't run and and/or it makes weird noises, there's a problem. Otherwise full speed ahead Ok, maybe that's an exaggeration.

Bentley Manual ref. Check for 12v at fuse S163(the one near batt). Check for 12v on socket nbr 2 of J52( Glow plug relay 180).