Calling all electrical gurus. Blind Circuit????

[69meadowlarkyellow 0]

Anyone know what the purpose of the blind circuit is in instrument power lead and how can you tell if it is the problem when you lose power to the instrument gauges when you plug in the connector. This is really driving me crazy. When I use a test light to check for power at the violet and black pin in the connector that plugs into the instrument panel I get power when it is not plugged into the panel, but when I plug the connector into the back of the panel, no power at the same pin. The only thing I can think of is that I end up with an open circuit for some reason and the schematic shows the black wire as a blind circuit whatever that may be.

[bnickel 10,004]

Anyone know what the purpose of the blind circuit is in instrument power lead and how can you tell if it is the problem when you lose power to the instrument gauges when you plug in the connector. This is really driving me crazy. When I use a test light to check for power at the violet and black pin in the connector that plugs into the instrument panel I get power when it is not plugged into the panel, but when I plug the connector into the back of the panel, no power at the same pin. The only thing I can think of is that I end up with an open circuit for some reason and the schematic shows the black wire as a blind circuit whatever that may be.

 

i don't have an answer for you but i think i have the same problem.

[69meadowlarkyellow 0]

I have even consulted electrical journals with no answers. Can someone maybe copy and paste my post on Stangnet. For some reason I can't post.

[69fastback 104]

If the test light works between that wire and ground when the connector is unplugged, but no test light when it's plugged in, that sounds like that wire is getting shorted to ground when you plug the connector in. I would trace the wire that it connects to when plugged in and see where it goes. If it is grounded instead of being connected to some load (lights, gauge, etc.) that could be it.

 

I noticed that your earlier post was about inoperative gauges. My guess is that this "blind wire" is connected to the output of the constant voltage regulator. When you plug in the connector, it causes the output of the CVR to be shorted to ground, and no power goes to the gauges.

[69meadowlarkyellow 0]

The blind wire is pigtailed into the same pin connector as the power wire in the connector.It would make sense if the CVR no longer showed power when the harness is plugged in, but why would the actual wire in the harness stop showing power. also if it is being grounded, wouldn't it blow fuses. I have tested the printed circuit for continuity along the CVR circuit and the sending wires for continuity and I get good readings. I have also tested the gauges and they all work when power is applied to the posts and through the printed circuit. Argh, I hate electrical problems.

PS, was anyone by chance so kind as to post this on stangnet. Just trying to reach a larger knowledgebase, not that I don't value your opinions and advice. You guys have been very helpful in the past.

[69meadowlarkyellow 0]

Well, I think I'm going to start calling the car Christine. Plugged the instrument bezel back in and suddenly it works. Who knows, as long as it works.

[69fastback 104]

Can I borrow your magic wand when you're done with it? :0

[69meadowlarkyellow 0]

I think that one of the terminals on the printed circuit was making contact with the housing. When I tested the power circuit and the housing for continuity, it showed continuity. Basically I loosened and retightened the posts and I can only assume that corrected the issue. Anyway, I,m still going to call the car Christine:) Thanks for the help.