Hi Paul - you may well have a bad OP switch. When they fail they can give some unpredictable results. But as per your testing, here are some thoughts:
Brosky said:
Ignition key is off. As soon as I tried to connect the ground, the AR valve started clicking and the connector on the OP switch was sparking (just normal stuff).
This would indicate a 'live' ground - which you should NOT have when the oil pressure is low.
Brosky said:
I switched the wires around, same issue.
Switching the wires around on the anti-runon valve will produce the same effect. The valve has no polarity, so it doesn't matter which wire is on which terminal of the valve.
Brosky said:
I go to the AR valve with test light and ignition turned off. Connect test lead to black and red wire going to valve and it's hot??? The other lead is dead. Why would red/black be hot with the key off?
This is correct operation. The red/black (red/brown maybe?) wire is hot when the ignition is switched off. This is not a problem. The problem is with the ground wire. When you say "the other lead is dead" I assume you mean it has no voltage on it, which it should not. But did you check that same lead (usually White/Purple) for continuity to ground? If you have continuity to ground on that wire, plus the red/black wire is 'hot' - then that, in fact, is your problem. You have a live circuit across the valve.
Brosky said:
Put the wires back to correct positions and I start the car, the ignition light works, brake light is out, but I never see the yellow oil light on. However, I do have great OP. Shut the car off and the valve is clicking on and off again with the key off (two or three times after shutdown).
Again, my apologies about the possible differences between Spits and TRs, but on a Spitfire neither the ignition light nor the brake light should have much effect on this problem (unless there is a short somewhere inside your wiring harness). The only commonality between OP, ignition and brake lights is that they go through the same fuse.
The oil pressure light should come on when there is low pressure and the ignition switch is 'On' (e.g. with the ignition switch On, but the engine not started), and it should turn off after the engine starts and oil pressure builds.
After you shut down, the AR valve should come on ONCE only (i.e. one 'click'), while the oil pressure switch senses that the oil pressure is still temporarily high. When the oil pressure drops it should click 'off' once. If it is clicking on and off multiple time you have an intermittent circuit or you have a bad valve. My guess would be intermittent circuit through the OP switch.
If you want to test the continuity of the OP switch it is very easy to do. Connect an ohmeter between the 'common' terminal and the OP light terminal. With the engine off (no oil pressure) this should show continuity. The common to AR-valve terminal should show NO continuity. With the engine running (oil pressure high), these results should be reversed.
If the terminal(s) on your OP switch wiggle, or if you suspect that the switch is not sensing oil pressure correctly, I would replace the switch. These are inexpensive (see other posts about GM replacements, about $10).
If you wire the switch backwards (reversing the AR terminal and the OP light terminal, but have the 'common' terminal correct) then you can get a condition that results in power on the AR valve and a permanent path to ground with the ignition off. If you wire it as per RomanH's post you should be ok.