URABUS WIRING TIPS

Q: What about the wiring harness?

It's a big job, I'll just leave it at that for now until we get more tips ready. I made my brother do most of it. Here's one simple tip. Don't try to keep the same wire-color along the length of the wire. It's very time-consuming and the return is dubious as you get more 'connections' thus more opportunity for failure. Just match colors at the ends. Use solder, not crimps because the rear wheels can splash water onto the harness. Make it very, very reliable.

Q: Hobert sez the tach is not compatible.

Subaru tach output is on the hairy edge of compatibility with the VW tach's requirements. Mine worked, Dick's did not so he devised a fix by adding a couple diodes in a simple circuit posted here, (printable) showing how to incorporate it into the Kennedy schematic.

A significant wiring tip: When building your wiring harness, locate the Subaru Read Memory connectors and a "check engine light" so they're accessible through the license plate flap. You will appreciate being able to check and clear engine codes without removing the engine lid. We'll get that measurement up soon. If you don't see it soon enough, email Tom.

Other

This is an unexpected bonus!! No more candlespots on the road. Subaru electrical system runs at 14+ volts, thus your headlights are now as bright as everyone elses!

After seeing this installation I am curious about your solutions to the error codes generated and stored by the computer. The owner of this "Eurabus", Brian, had installed the switch that Hobart recommends to turn off the error light on the dashboard. He had also wired up a reset button at the dashboard to reset the computer and dump the stored codes.

How did you handle this situation?

I haven't installed a "check engine" light on the dash yet. I put a small 12V green LED (Radio Shack) on the upper right corner of the VW engine harness box (front left of engine compartment). Its output is viewable from the license plate flap opening. I use the stock Subaru "Read Memory" and "D-Check" connectors in the engine compartment to dump/reset codes. I plan to put a "check engine" light on the dash in the unused LED spot (next to other dash LEDs), but will probably leave out the switch as I intend to have no on-going trouble codes.

By the way, newer Vanagons have (post conversion) one or two unused wires which go from the engine compartment to the dash area ('91 may have more??). One was used for the ESC Malfunction dash light ('88 and up, could use this wire for "check engine") and the other was used for the oil pressure light circuit ('86 and up). Subaru uses one oil pressure sender (as do '85 and below Vanagons). '86 and above Vanagons (2.1L Digifant engines) have two senders, high and low pressure, plus some circuitry in the instrument cluster to interpret the two signals. I played around with it a bit to determine how to wire in the single Subaru signal and ended up simply tying into the low pressure signal line (I'm not positive now, but you can experiment which works). This frees up another wire which goes from the engine compartment to the instrument cluster. I intend to use this wire for my check engine light. I used the other for my parking switch.

I got rid of the "Parking Switch" and "Neutral Switch" error codes by installing a parking brake switch and clutch switch. The computer just wants to "see" the signals move from one state to another (0V and open, ~8V for an A/T computer) from time to time while the engine is running, but not moving, to decide that the switches are OK. Operationally, the engine runs higher during warm-up when the parking switch or neutral switch are active.

For the parking brake switch, I replaced the stock switch (turns light on dash) with one that has two separate circuits. I got it from the VW dealer awhile ago for another project (perhaps it was for a Jetta or Rabbit or something). When the parking brake is applied, the switch shorts the computer input to ground. If you have a computer from a M/T Subaru, I think you have to open the line when the brake is applied (which would be difficult with this switch). Same goes for a clutch switch input on a M/T computer. Anyway, I've since removed the clutch switch I installed (Neutral switch computer input) and intend to connect the computer input through a diode to the parking brake switch. This allows one switch to operate both computer inputs, but keeps them isolated from one another. If I has a computer from a M/T car, I'd probably keep the clutch switch.

I built a speed sensor from the EGR/O2 elapsed mileage counter module, which is located on the speedo cable near the left front wheel (on non-synchros, anyway). The speedo cable from the front-left wheel and the speedo cable that goes to the speedometer both attach to this module (via a shaft that runs through it). Once removed (1 bolt and speedo cables), it is held together with four small screws. The module already has 12V and gnd, so you can make a speed sensor with one wire. As if you really care, the EGR/O2 elapsed mileage function of this module is not compromised by the speed sensor function, though you'd have alot more room if you gutted the box. You could get another module from a wrecking yard to experiment with (recommended, but could set you back $10-$20).

The computer expects a signal that alternates between 0V and 5V four times for every wheel revolution. Subaru uses a reed switch built into the speedometer with some associated de-bouncing and amplification circuitry. My first generation used the same approach. I roughed up the shaft and epoxy-puttied four little magnets (like Radio Shack Rare earth magnets, 4/package) to the shaft near the lower end (wheel side).

I drilled a hole at a right angle to the shaft at the very bottom of the module and poked through a Radio Shack reed switch ($3, used for security systems) so that when the module is reassembled, the reed switch comes to within 1-2mm of the rotating magnets. Test the set-up before gluing the switch in place.

You need to use the 12 and gnd. to generate 5V. For this, use a 5V regulator (7905?, looks like a big transistor) from Radio Shack. It's cheap easy to use. One side of the switch should go to +5. The other side should go through a resistor to gnd. and to a digital circuit which will buffer/amplify and possibly debounce the switch output. You could probably use a simple TTL or CMOS inverting ('04) or non-inverting amp for this. I grabbed a version that has schmitt-trigger inputs, but haven't installed it yet.

A probably better approach would be to use a Hall Effect sensor instead of a reed switch. You'd use the same magnet set-up, but somewhat different electrical interface. I like this approach because the sensor can't wear out like a reed switch. However, it may be slightly harder to interface to. Radio Shack has some little books which show you how to get a digital signal out of a Hall Effect sensor (simple schematics and such). They don't normally stock the sensors, but you can order them through their catalog. I didn't use this approach because I wanted to build it right now and didn't have the patience to order parts.

Dick's speed sensor crapped out (reed-switch) so he bought a speed sensor from www.weirdstuffwemake.com. Here's the email just in case the website is down: luminous@weirdstuffwemake.com

Operationally, it idles higher while you're moving and presumably uses an electrically actuated vacuum switch to suck fuel vapors from the charcoal canister vice the vacuum-operated method Hobart/VW uses. I removed the VW vacuum switch and plugged its source in favor of the Subaru method (using a vacuum line reducer from an auto parts store) once I got the speed sensor working. I think it is related to the periodic "engine dies when coming to a stop" problem which plagues some Subaru conversions (mine included). I hypothesize that the Hobart/VW operation of the charcoal canister looks to the Subaru computer like a vacuum leak under some circumstances. My engine hasn't died yet since installing the speed sensor and re-rigging the charcoal canister plumbing.