$80 Glow Plug Harness?! Not on My TDI!

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This is the original, poorly-built, overpriced piece-o-crap that VW sells.

It's been a bit since I've last posted on this blog.  I've got some things going on that I've been hoping to share, but things haven't panned out, yet.  I hope to make an announcement about some changes I'm making in life soon.  Soon!  Meanwhile, I'll just say I've been quite busy on a project.

Additionally, my kids and I have also been working on a quadcopter, now that building a 3-axis stabilized platform is really pretty simple and inexpensive.  When we get it flying I'll post a video and blog on that project.

We've had an unusually harsh winter here in Indiana, so I've been driving the diesel-converted Suburban [aka the Zombie Apocalypse Command Center (ZACC)] quite a bit.  When road conditions allow it, though, I save fuel by driving my 2001 Jetta TDI (ALH).  Sure, the Suburban gets reliable economy in the 20s, even in four wheel drive, but the VW moves me around with economy in the 40s.  Paying half as much to commute is a good thing, even if its in a beat-up little car with 260,000 miles on the odometer.

Because temperatures have been low, glow plug function has been important, and I recently noticed some issues with cold starts.  Making a cloud in a parking lot with a rough-sounding engine is embarrassing!  I often cycle the key on-off-on in order to increase glow plug heating before cranking the engine.  Recently it didn't help, so I pulled the VW glow plug harness off and checked continuity for all four plugs.  Last year one of them died (no continuity) and replacing it made a huge difference.  All four plugs checked out OK, this time, so I figured my problem was another bad glow plug harness.

The glow plug harness on these vehicles is a poorly made plastic molding with only two conductors inside.  One conductor feeds the positive side of glow plugs #1 and #2, while the other takes care of #3 and #4.  Engine grounding completes the circuit for these plugs.  I've been reading a number of complaints about them going bad repeatedly because the actual connections get corroded at the glow plug terminal.  Bad design!  I've already replaced this part once.

Being a bad design is one thing.  Paying $80 per copy is another!  I hunted down the part number and searched all over the Web for a better deal.  Prices varied a bit, but they never went south of $50, so I decided that they were all horribly overpriced for a simple component that I could build myself.

I measured the connection on the dead glow plug from last year (not sure why I kept it, but it came in handy).  It came in at exactly 4mm and my recent multicopter work got me thinking about 4mm female bullet connectors.  I went onto eBay and bought a dozen sets of gold-plated male and female connectors for $5 delivered.

This harness was made from 4mm female bullet connectors soldered onto 12ga wire with heat shrink (and some electrical tape--needed some larger heat shrink).

When they came in, I pulled off my VW plug harness to judge the needed wire lengths, soldered the 4mm female connectors onto the business ends of some wires spliced into a pair of Ys, covered everything in heat shrink (OK, yeah, some of it is actually electrical tape...for now), and spliced these assemblies into my wiring harness.  The bullet connectors were just a bit loose on the plugs, but I solved that by squeezing them ever so slightly with a crimper.  Now they fit onto the plug electrodes more tightly than the original harness does.

And, of course, my homemade harness works beautifully!

--No more embarrassing smoky, rough startups!