Findings

I have learned a few things about the next steps on the electrical from my thread on TDIClub. I wanted to post these findings so I don't lose them (and so everything is in one place). First, I wanted to send a congratulations to Hal. Over the past few months, while I have been slowly tryingto get my bus together, he has installed a water-cooled gasser engine (VW straight 4) into his bus. This was a simpler install, but he still had many of the same challenges: radiator placement, adapter plate, some clearance issues, etc). I got an email from him the other day tellnig me that he test-started his engine. He hasn't been able to test-drive it yet, but he is very close. So, congratulations, Hal. I'm proud of ya, and you're inspiring me to keep going.

Firing the Starter
I mentioned in my last post that I extended the wire that runs from the main harness to the starter. This wire is set to 12V by the computer (ECU) when the "X" circuit is powered. This was the case on the old bus just as it is on the NewBeetle. I guess some things never change. Anyway, I need to notify the ECU that "X" needs to be powered. To facilitate this, I extended a wire from near the starter (where the original "X" wire terminates) to the ECU. This wire needs to power a pin, or somewhere in the ignition plug. I'll piece that together tomorrow.

Trigger "run" to computer (ECU)
Somehow the ECU needs to know that the main switched power has been activated. Most of the electrical system is turned on or running when the ignition switch is at this point. On the old bus, having the switch here allowed the heater blower to turn on, the windshield wipers to work and the exterior lighting. That's it. Talk about old-skool simple. With the computer system controlling everything, this is one of the more important things to communicate into the box. Like the "X", this wire needs to power a pin, or somewhere in the ignition plug.

I have taped-up a 3-wire bundle that will send this signal down to the computer on one wire, and the 12V state of the next 2 sections below on the other 2 wires. Unlike the rest of the wire bundles, this one will run inside the bus along the drivers side of the body from by the clutch pedal to the westy closet where the ECU is hiding.

Check Engine Light (CEL)
Probably the most important indicator light on the TDI engine is the Check Engine Light. This light illuminates whenever any code is thrown by the computer (ECU). In order to run safely, you need this light operational. I will be installing a small LED inside the stock bus dashpod so it is visible while driving. To power the LED, one side needs to be connected to "circuit 15" (aka switched power) which is 12V when the ignition switch is turned to "run". The other side of the LED needs to be connected to pin #43 on the ECU. When the ECU throws a code, pin 43 is grounded, lighting the LED. Otherwise, the pin is set to 12V.

Glow Plug Light
Second in importance only to the CEL, is the glow plug light. This light tells the driver when the glow plugs have satisfactorily warmed the combustion chambers. If there is a problem in the glow plug circuit, the light flashes. Next to the CEL, I will be installing an LED for this. Like the CEL, one side is powered from the switched power (15) for 12V. The other side of the LED needs to be connected to pin #41. Like the CEL, the computer (ECU) grounds the pin to send a signal, and sends 12V to turn it off.

Tomorrow is Friday which means it is early-release day. Hurrah! I should be able to get the wire bundle in and wired up. I need a pair of LED holders, and I'll have to pull the dashpod to make holes for the 2 LED's, but I'll probably wait on that until I've confirmed that the wiring works. That's it for today. Again, congrat's to Hal for getting his engine started. I hope to hear of a test drive one day very soon.