Hi Dave,
I agree that it is time to move the discussion onto a new start point. I will begin by pasting your last commentary here. BUT to begin with I have another baffling development to report. After my last post to you I had my wife check the other two brake lights to see if they were still working and the answer was yes. And then I realized I had not replaced the bulb sensor when I was doing the check, i.e., the two main brake lights were working without the sensor even being in place. A mystery wrapped in an enigma, etc.


You're not going wrong at all, in fact this is slowly starting to come together. Your earlier testing showed the brake light circuit of the new bulb sensor seems to work and the old sensor may well be faulty.

Your testing is now showing you're not getting power from the brake light switch to the realy tray. That indicates a faulty brake switch exactly as I alluded to in my last reply. Dealing with two problems at the same time may well have been confounding the issue for you in amongst trying to master new electrical testing techniques.

If you can confirm that you're not seeing a reliable 12 volts in the socket for pin 54 then that now moves your attention to a faulty brake switch, as I alluded to in my last post. I'd suggest using a wire wrapped around pin 54 for testing so you don't have to worry about making sure the tip of your meter probe is contacting properly in the socket as it can be a bit awkward to see what you're doing in there. Try the pedal a number of times slow and fast as worn/dirty internal contacts may make for an intermittent signal or less than full battery voltage (compared to the direct from battery voltage you can see at fuse 3). Use an ohms setting, not a continuity beep setting. Now if you somehow do happen to see 12 volts then I'll be shocked if you're not also seeing some brake lights at the same time, hopefully even the 3rd brake light.

Post back once you confirm it's now at the brake light switch. I would suggest starting a new thread at this stage as this one is getting horridly long and off the original 940 radio removal issue. I'll pick up your problem there and try to help you through brake switch replacement if needed as the new style switches are indeed a bit tricky to deal with.
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