Power to TCc 7801 ignition switch

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Mark Strang
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Location: Williamsburg, Virginia, USA

Power to TCc 7801 ignition switch

Post by Mark Strang » Sat Mar 09, 2024 5:28 pm

Need a bit of help. Just completed the wiring of TC7801 without flashers using W.75781 which is in the Instruction manual. Prior to energizing the system I checked most of the circuits and all was good. When I connected the battery, all of the lighting circuits worked but the ignition warning lamp was not lit nor would the fuel pump etc work including the engine. I removed the dash and spent four hours checking each wire to make sure they were correct. I even installed a different control box to eliminate that as a possibility. All seems correct. It just appears as if the ignition switch is not getting power although the lighting systems work. The switch checks out fine, when the key is turned and as mentioned, the lights work. Continuity is made from "A" to "IG" so the system should go hot. I don't understand how I can have power to the lights and not the ignition/petrol, etc., circuits. Any ideas? I'm hoping the problem is something simple. There's not much to the whole wiring package. Missing a ground perhaps? I can figure out mechanical things pretty well but struggle with electrons. I've rewired a couple of TD's without a problem but this one has me stumped.

Mark

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Rob Reilly
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Location: Indiana, USA

Re: Power to TCc 7801 ignition switch

Post by Rob Reilly » Sat Mar 09, 2024 7:49 pm

I wonder if for a TC without flashers you should be using diagram W70482?
Have you checked the fuses?
1937 TA 1271

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Mark Strang
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Location: Williamsburg, Virginia, USA

Re: Power to TCc 7801 ignition switch

Post by Mark Strang » Sun Mar 10, 2024 6:00 am

Call off the wolves! My wife came down to the shop last night and asked what the problem was. I explained that I got power to everything except what was supposed to start the car, that the wiring was correct, but it still wouldn't start. She simply said it "had to be the switch" and suggested that I jumper across the switch. In an effort to make her happy and prove to her that the switch wasn't the problem since I had checked it out, I simply jumpered it out and the car came to life!!! Apparently the switch that had been rebuilt 25 years ago along with the other instruments, must have had enough oxidation on the contacts that prevented current to flow. Once I hit it with voltage they cleaned up enough to pass current since the switch now works without the jumper. Sue simply smiled, asked for a "thank you" and walked away with one TC owner feeling very embarrassed. Love that woman!

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Steve Simmons
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Re: Power to TCc 7801 ignition switch

Post by Steve Simmons » Sun Mar 10, 2024 7:28 am

Keep the wife, replace the switch. :D
1949 TC8975 / XPAG 9609
1948 TC6011 / XPEG1182 (XPAG6472)
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