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Member
Posts: 35
Location: Yakima, WA | hello,
just purchased a vehicle, 55 plaza. working on small various things and I just got the 12v conversion done and the new 12v bulbs in and fuse block wired up. The good news: the new bulbs work and my parking lights work.
The bad news, my brake lights dont work.
So having just purchased my shop manual I start reading and locate the brake switch coming out the back of the master cylinder. I use my multimeter and find 12v going into the switch, and then 12v coming out of the switch when the pedal is resting (not being pressed).
I expect the switch to have 12v only on one side, until the pedal is pressed and then it should energize the other side. at least in theory thats how I believe it should work.
what am i missing?
I have a meter and aside from jumping the entire wire harness to 12v to verify the bulb is seated correctly in the bulb socket I am not sure what else to check to see why its not lighting up.
BUT that doesnt solve the brake switch showing voltage on each side/wire.
Edited by HerbertsNatural 2015-03-28 1:38 PM
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Expert
Posts: 3776
   
Location: NorCal |
Your thinking is correct, there shouldn't be 12V on both sides of the switch with the pedal relaxed, only when the pedal is depressed. A simple adjustment of the switch might be all that's needed.
The way it is now your brake lights should be on constantly. Power leaves the brake light switch and goes through the turn signal switch so you might have two problems, the brake light switch and the turn signal switch. |
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Veteran
Posts: 119
| The stop light switch is hydraulically operated by fluid pressure in the brake lines. These switches are famous for going bad, and even today hundreds of them are available. Use a 12V light bulb to test voltage, a meter draws no current and won't really give a reliable indication of continuity. The brake light switch supplies voltage to the turn signal switch when the brakes are applied. So a bad connection at the turnsignal switch will disable the stop lights and not necessarily the blinkers.
 (Turn Signals Wiring 55-002.jpg)
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 Turn Signals Wiring 55-002.jpg (129KB - 168 downloads)
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Member
Posts: 35
Location: Yakima, WA | Thank you for the help guys! And yes my turn signal switch is not in good condition it appears to be missing the entire inside cam and plate and even the handle for it. But the wires do appear to be present.
I got my meter back out and actually tried to run some more tests. My readings I thought I had found before appear to be reading different today. Today the switch was open and was not functioning.
I was able to power the circuit that provides power to the brakes and then jump the two wires at the switch with a fused jumper wire and I was able to verify the brakes were working that way.
Now I have a new master cylinder ready to go in, looks like I gotta add a brake switch to the job too.
As far as the blinkers I am trying to find a universal style blinker I can attach to my steering column and wire to the existing wires already there. I just checked them all and they appear to be working and all accounted for.
Edited by HerbertsNatural 2015-03-28 9:07 PM
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Member
Posts: 35
Location: Yakima, WA | ordered a new brake switch and a heavy duty universal blinker switch so I'll have those on the way soon. |
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Member
Posts: 35
Location: Yakima, WA | One more question,
I got the brake switch installed into the new MC but there is a small amount of leakage through the threads.
Before I go tighten it some more I want to ask:
Is there a thread tape I should use on the brake switch and brake line going into the MC or is it designed to be metal to metal contact?
I wanna use some tape but not sure how well the DOT3 brake fluid would do on Teflon tape.
Thanks!
Once I get the answers I can reinstall the switch and bleed my brakes. Last step before I get to drive this plaza for the first time :))
Btw blinkers work beautifully once I put in the 12v flasher (with the 6v one it wouldn't flash only light up.) |
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Expert
Posts: 3393
Location: Chestertown, NY ( near Lake George) | Dot3 has not affected the fittings at the master on my cars, but use sparingly. |
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Elite Veteran
Posts: 907
Location: Magra, Sweden | Frank, did you keep the positive ground when switching to 12V? When we got our 55 La Femme brake lights didn't work and I found out they've switched polarity by connecting the battery to negative ground. Consequently the brake switch connected ground to ground when braking. |
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Member
Posts: 35
Location: Yakima, WA | no i went to negative ground. it was pretty straight forward. I did end up having to replace the brake switch. I got all the wiring figured out and it all works, electrically speaking.
having one hell of a time with the brake bleeding though. making a new post. |
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question about brake switch 1955
