Just thought I'd share this simple mod that I installed today.
Referencing David Delman's bulkhead guide here: http://www.dmcnews.com/Techsection/p...Connectors.pdf
The wires for the wide open throttle (WOT) switch and the A/C clutch coil are in the same bulkhead plug. This makes it fairly easy to install - without any permanent wiring changes - a relay in-line that cuts off the AC compressor when going full throttle. On a stock motor this could help get just a little more "oomph" to pass. On my turbo car I use the WOT signal to put the lambda ECU in "open loop" mode via Hobbs switch. So now whenever I'm at WOT or in boost the AC will automatically cut off to decrease engine load.
Parts needed:
-A 7-pin Lucas style plug set with both male & female connectors and pins:
Example: http://cgi.ebay.com/ws/eBayISAPI.dll...m=131269455820
-A single 30A/40A automotive relay with normally closed contacts (the 87a terminal). A prewired plug saves a lot of time here.
-A single decently large diode, like a 1N4001, or any large-ish power supply diode.
-6 or 7 lengths of 14ish gauge wire (6 for manual, 7 for auto). I used a random bunch of spare wire, using larger gauge wires on the starter solenoid and alternator light connections. The remaining terminals are low current gauge senders.
Tools:
Wire strippers
For-real proper non-insulated crimp terminal tool. Don't use those $20-with-terminal-assortment jobs. Borrow one from Autozone if they have it.
First sort out the two plug halves. The new female terminals will connect to the firewall bulkhead terminals and the male terminals will connect to the existing wiring harness.
Mostly you are making an extension cable and simply strip, crimp, and insert the appropriate terminals into each plug housing. Remember they are a mirror image of each other, so you might want to clip the connectors together so you can tell visually that you aren't crossing wires. I'm not sure what would happen but it would probably be bad.
The altered connections:
-The topmost lone pin, pin 28 in Dave's PDF, is the AC signal (pink wire in harness). One end connects to relay 87A and one end connects to relay 30
-Also connect relay 85 or 86 to the AC signal at the bulkhead plug, or just trim the insulation back on the bulkhead wire from the previous step and splice it in-line. This provide 12v for the relay coil and will only be active when the AC is on. CONNECT IT TO THE BULKHEAD TERMINAL SIDE. If you connect it to the harness side the relay will go into buzzer mode during WOT.
-The other relay terminal 85/86 (whichever you didn't use above) gets connected to the WOT switch wire (light green, pin 33) and will need to have the diode placed inline with the bar on the diode facing away from the relay.
Why the diode? Turns out the lambda ECU is very sensitive to anything resembling ground. if you don't use the diode it will see ground through the AC compressor coil and your frequency valve duty cycle will be stuck at 66% constantly.
Picture of harness from before discovering the need for the diode. The wire colors don't correspond to anything, they are simply from my drawer of various lengths of wire.
IMAG0925.jpg
Not so good installed pic. Also featuring misused zip-ties to keep coil from slipping down in coil mount
IMAG0930.jpg
To test, turn on AC and manually push WOT switch. Compressor should disengage. Secure the wires & relay and you're good to go.
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