70 Bug minutiae

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Psucamper
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Location: Boalsburg PA
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70 Bug minutiae

Post by Psucamper » Thu Aug 27, 2015 5:49 pm

I'm rewiring a 1970 bug and upgrading to 1972 (and up) electrics. Want all the functions on the steering column instead of on the dash. My current difficulty is with the push to test brake warning light on the dash. It's the old 3 prong assembly with the red wire from the master cylinder,a black wire from (+B) and a brown wire to chassis ground. Tested it and there is no light. Surely VW made the bulb replaceable but I can't find out how. I twisted the center section to see if it has a locking detent or something but no go. Anyone have experience with this type of assembly? Bob

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Amskeptic
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Re: 70 Bug minutiae

Post by Amskeptic » Thu Aug 27, 2015 9:11 pm

Psucamper wrote:I'm rewiring a 1970 bug and upgrading to 1972 (and up) electrics. Want all the functions on the steering column instead of on the dash. My current difficulty is with the push to test brake warning light on the dash. It's the old 3 prong assembly with the red wire from the master cylinder,a black wire from (+B) and a brown wire to chassis ground. Tested it and there is no light. Surely VW made the bulb replaceable but I can't find out how. I twisted the center section to see if it has a locking detent or something but no go. Anyone have experience with this type of assembly? Bob
If you have 1972-up electrics, do you have the later master cylinder switches that work with the no-longer-push-test brake warning light that actually has an elementary logic circuit on the back with four terminals including a "k" terminal?

I tried to remove the bulb from an early warning light and could not do it.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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asiab3
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Re: 70 Bug minutiae

Post by asiab3 » Thu Aug 27, 2015 9:20 pm

Amskeptic wrote:
Psucamper wrote: I tried to remove the bulb from an early warning light and could not do it.
I second that, though used ones pop up from time to time. I think I grabbed a few for $5 last year.
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

kreemoweet
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Re: 70 Bug minutiae

Post by kreemoweet » Fri Aug 28, 2015 5:22 am

Those early brake warning lights use the same bulb holder as the early bay instrument lights/warning lights. Rotate 90 deg. counterclockwise and pull out to
remove. I can't imagine why yours won't come out. Are you sure the thang is wired correctly? Quite frequently, people see how the wiring is illustrated in some of the
Bentley diagrams, and get the (wrong) idea of which wire goes to which terminal. You can test the bulb filiment with an ohmmeter, without removing it. The little
diode inside is very often open, and the bulb won't respond to a signal from the brake light switches, but the push-to-test feature should still work.

Image

Psucamper
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Re: 70 Bug minutiae

Post by Psucamper » Sat Aug 29, 2015 4:13 am

Mr. K Thanks for the reply. I did try to remove the little bulb holder assembly but failed because I didn't apply enough torque. Chickened out for fear of breaking a hard to find part. Second try worked as you said. Interesting that the integral bulb holder is identical with the other panel parts. Cleaned 40 + years of corrosion and dirt and brightened metal contacts. All well now. That little warning assembly is a testament to quality engineering and build.

kreemoweet
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Re: 70 Bug minutiae

Post by kreemoweet » Sat Aug 29, 2015 8:10 pm

Hard to find? Search the interwebs for "141 957 397A" and see for yourself! The bulb is N177512. Now, the version of that bulb holder with 2 of the little male tab
connectors, THAT's hard to find.

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Amskeptic
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Re: 70 Bug minutiae

Post by Amskeptic » Sun Aug 30, 2015 4:35 pm

kreemoweet wrote:Hard to find? Search the interwebs for "141 957 397A" and see for yourself! The bulb is N177512. Now, the version of that bulb holder with 2 of the little male tab
connectors, THAT's hard to find.
I think he was talking about the bulb holder assembly vs just the bulb . . . .
I did try to remove the little bulb holder assembly but failed because I didn't apply enough torque. Chickened out for fear of breaking a hard to find part.
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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