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| Brake proportioning valve (Page 2/2) |
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sanderson231
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FEB 09, 08:45 PM
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| quote | Originally posted by Duck 1:
Took the plug off of the pro. valve. Put a test light in the center hole and put the other test light wire against the other switch wire in the plug . There is no power getting to the por. valve switch plug. What is this foil you are talking about in the wiring harness and where exactly is it located ? |
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My bad - forgot that the brake light is grounded in parallel. As long as the brake light is on you should not see 12+ volts at the center hole of the prop valve connector. There is a 12 volt drop across the brake light so every thing downstream of the light should be a ground. If the brake light stays on with the prop switch unplugged, there is a path to ground somewhere else. The most likely place is the parking brake switch. I know that it is a PITA but you need to unplug the parking brake switch and see if the brake light goes off. If the light goes out the parking brake switch is the culprit. If the light stays on then try unplugging the chime box. A fault in that box could be providing a ground causing the brake light to stay on. If unplugging that does not cause the light to go out then go to the trunk release relay if there is one (ignore if your car in an automatic). The trunk release relay coil is in series with the parking brake switch. This is to prevent using the electric trunk release unless the parking brake is set. If the relay coil has a fault to ground that could cause the brake light to stay on. So the next step is to unplug the trunk release relay. If all this fails to turn off the light then there is a fault in the wiring. The copper foil I mentioned is inside the sockets where the wiring harness plugged into the instrument panel. These can get detached from the socket and cause a cross connection when the plugs are reinserted. If you remove the instrument panel the copper foil is obvious.
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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Duck 1
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FEB 10, 08:08 AM
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I have a automatic so the trunk release relay should not be the issue. The blue chime box (under passengers side dash ) has been unplugged so that eliminates that. Since the brake light stays on it must be in the dash wiring panel as you suggested. All of your suggestions have been very helpful so I guess it's dash removal time , UGH , not looking forward to that !
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theogre
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FEB 10, 09:21 AM
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Just remove the back cover, Carefully Unplug big connectors then use small mirror or camera to look at copper in the hole. B-light involves mostly bigger one on outer side middle the contacts.
Can't see exactly what other bulbs right now and have to go somewhere can't look up now. Think 1 is another "idiot light" and other go to some dimmer dash lights + or −[This message has been edited by theogre (edited 02-10-2023).]
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ArthurPeale
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FEB 10, 01:10 PM
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| quote | Originally posted by theogre:
Just remove the back cover, Carefully Unplug big connectors then use small mirror or camera to look at copper in the hole. B-light involves mostly bigger one on outer side middle the contacts.
Can't see exactly what other bulbs right now and have to go somewhere can't look up now. Think 1 is another "idiot light" and other go to some dimmer dash lights + or −
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What Ogre said, removing the cluster isn't a big deal. While you're in there, may I suggest doing the temperature gauge wiring fix ? You're already 3/4 of the way there, you might as go all the way.
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