Musical Instruments

More from last weekend... a while back I talked about adding a second OBDII plug output up at the steering wheel.  Knowing that I wouldn't have the TDI dash-pod up front at any point in the near future, I figured I needed some instrumentation.  If you haven't seen the instrumentation on an old bus, Lemme paint a picture for you.

Original Bus Dash
On one side, you have the speedometer.  Next to it is the fuel gauge and on the other side you either have an analog clock (if you own a deluxe) or a big blank spot.  The fuel gauge also is home to all the other "instruments".  First, you have the turn signals.  When you turn on the flashers or fiddle with the turn signal arm, both green arrows flash.  Neat, eh?  Yes, and only a little confusing to a first-time bus driver.  Below the green flashers are 2 "idiot" lights.  The OIL light lets you know when you're out of oil, or your engine is about to explode.  If this light flickers, you need a rebuild, but if it lights up nice and bright, your oil pressure has dropped below 3psi and you're basically hosed.  Shut off the engine, its already dead.  The other light (GEN or ALT) lets you know that your electrical system is in trouble.  Like the OIL light, a fully lit buld means you're basically hosed, electrically.  A dim light means your alternator or generator is failing to produce a full 12V (it should be more like 14V, really).  A flickering light means you have regulator issues, but a full light could mean a bad alternator or a bad regulator.  There could be other reasons too, but those are the 2 most common.

Going above Stock
Why am I going on about this?  Well, those lights won't do my any good with this TDI engine.  Many original-engine drivers add gauges for exhaust temp and oil pressure, a tach, maybe other things.  So, this isn't terribly out of character for a bus.  Rather than spend a small fortune on different monitoring gauges, I wanted to do something a little different.  First, I thought "wouldn't it be neat to be able to plug in the VAG-COM on my laptop and use that".  I've since purchased an UltraGauge, which has all kinds of meters and things on it.  Most importantly, it has the coolant temperature on the front page, which is the most important one at this point.  So, on to the extending of the OBDII...

Add a Plug
I bought a made-in-China 3-wire OBDII output plug.  The plug was poorly documented (as was mine of the install), but I'll try to cover that a little bit now.  The plug has 3 wires: red for switched B+, black for ground and blue for the signal from the ECU.  From the original OBDII plug, the brown/white wire needs to be tapped into and extended.  I had run a few extra wires from front to back, and with the interior all torn open, the tie-in (after figuring out what to do) was pretty easy.  In an earlier post, I showed a picture of an early mounting.  I've since removed it from the e-brake mount and moved it up into the stock-radio hole.  It needs to be a-fixed, but that should be relatively straightforward once I get around to it.  I need to figure out what I'll be using that hole for before I do that.

Add-on OBDII Testing
Actually testing the install turned out to be very easy.  Apply B+ to the red wire.  Plug in the UltraGauge.  Turn ignition key to run.  Wait.  It was at this point that I discovered that my engine harness efforts were not yet complete..... much to my dismay.  The P-codes returned.  I swapped Justin's borrowed engine harness in again, and the codes lingered, but it may have been because the ECU remembered them from before.  So, I figured I missed a bad wire and completed the verification of the harness, even some wires I had no reason to believe were bad.  This is where things got interesting.

Broken Harness.  New one needed
I documented every wire, and verified connectivity through them all.  I'll convert the documentation to a colored drawing later, but the important bit is every wire was confirmed.  When I put the original harness back in, not only were the codes back, but now the ECU thought my engine temp had increased from ambient (69*) to 419*.  Clearly, that wasn't right, but it was telling.  I think my efforts to diagnose the problem actually caused the problem.  Argh.  I've spent a few hours trying to find a replacement plug or harness, or some other solution, but I think in the end, I'll be needing to buy another harness at a premium - eBarf prices.  Sigh... I did mention I was flat busted in my last post, so that won't be happening soon.  Rather than cut up the borrowed harness so it can receive my oil pressure signal, I may take short flights in the bus to see if the fans come on when they should.  I figure it shouldn't take much driving to figure it out.  I'm afraid of losing my window of opportunity this summer.

That's it for today.  I still have one last chunk of effort from last weekend to talk about.  I've had the boys this past week and it's been awesome.  Lots of computer gaming and movie watching after days of heavy play involving camp and hitting the apartment complex pool.  They head to their mom's on Sunday, and I'll be returning to bus work shortly thereafter.  Thanks for following along...