sorting out the electrical - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
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post #1 of 12 (permalink) Old Jun 18th, 03, 07:29 AM Thread Starter
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Todd
 
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Hello all, still sorting through all the little electical gremlins in my 67. Have most of the major items figured out. Now its the little stuff. Right now, the dash brake light is on and stays on whenever the ignition switch is on. I've played with adjusting the little stop plate on the emergency brake switch to ensure that it is coming all the way back, but to no avail. Do I replace the switch, or could it be something else?

Todd

Bolero Red/Black 67 rs/ss, 350 4-sp, Deluxe interior, slowly becoming a restomod
Aqua blue/White 77 LT Type, Built 305 auto, in the restomod process, wife's car since high school.
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post #2 of 12 (permalink) Old Jun 18th, 03, 07:42 AM
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If you disconnect the switch on the emergency brake and let it dangle, does the light go out? If not, check the differential pressure switch below the master cylinder. Could be that you've got a brake system pressure problem in front or rear. It's also possible that the shuttle inside the valve is stuck, keeping the light on. Disconnect the wire there also and see if the light goes out.

-dnult
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post #3 of 12 (permalink) Old Jun 18th, 03, 08:44 AM Thread Starter
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Todd
 
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dnult,
You just jogged something in my memory. When I was first bringing this car back to life, I remember taking her for a test spin after I had just got it running again. Before I left the garage, I noticed that a wire was hanging below the master cylinder that had been disconnected. I reattached the wire to the master cylinder, fired it up and headed down the driveway. By the time I reached the end of the driveway, I noticed a burning wire smell and the car died. I jumped out and opended the hood and that wire that I had reattached was smoking. So I disconnected the wire, jumped back in and the car fired back up. And I haven't done anything with it since. Could this be the source of my problem, and what would cause that to happen? Bad ground?

Bolero Red/Black 67 rs/ss, 350 4-sp, Deluxe interior, slowly becoming a restomod
Aqua blue/White 77 LT Type, Built 305 auto, in the restomod process, wife's car since high school.
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post #4 of 12 (permalink) Old Jun 18th, 03, 02:10 PM
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Wow! If it was in fact the brake light switch...hmmm. Can't imagine what would do that unless the bulb was a dead short to 12volts. The current through that line should be limited by the bulb to a less than 300 milliamps. For that matter, the circuit should be fused well below what it takes to fry the wire. Are you sure that was the correct wire for the brake?

As for bad grounds, normally no - bad grounds won't cause wires to fry. On the other hand, if you have a totally bad ground in your electrical system and that wire was the only source of current flow to the rest of the system, then maybe. I doubt it though. Sounds like something is seriously shorted, but I can't offer much to help. I'd probably start by doing some resistance measurements. What is the resitance to ground of the fryed wire? Maybe it would help to isolate the problem if you separated the fuse block connector at the firewall. All I can say is wow.

-dnult

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #5 of 12 (permalink) Old Jun 18th, 03, 10:43 PM
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Sean
 
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hey dnult, i believe the actual brakelight switch is under the dash, a plunger switch, mounted to the brake pedal assembly (unless thats not what you meant). the wire attached to the sender on the master cyl is for the brake low pressure warning light in the gauge cluster. it should be a tan 18awg wire. i'm pretty sure thats how my 68 is, but i havn't worked on that area in some time. so if its how i recall it, that wire still shouldn't have smoked, even if it was a bad sender the light would just turn on in the dash. hmm, since that wire just completes the circuit when the sender closes, i can't imagine off hand why it would smoke when you hooked it back up. that may also be why it was unhooked to begin with. my first approach would be check voltage/resistance measurements as dnult stated, and just trace that wire all the way back, and check that switch on the parking brake, it should be the same circuit, and it could have gone to ground at the switch, due to a bad switch. do like dnult said and disc. the p brake switch, and test the wire hanging by the master cylinder, see if there is a change. maybe pick up an assembly manual with a wiring diagram to assist you. good luck with it!

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

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post #6 of 12 (permalink) Old Jun 19th, 03, 03:23 AM Thread Starter
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Todd
 
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Thanks, guys. I'll get the multimeter out and see what I come up with.

Bolero Red/Black 67 rs/ss, 350 4-sp, Deluxe interior, slowly becoming a restomod
Aqua blue/White 77 LT Type, Built 305 auto, in the restomod process, wife's car since high school.
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post #7 of 12 (permalink) Old Jun 19th, 03, 01:08 PM
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I probably should have said brake warning switch instead of brake light.

-dnult

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #8 of 12 (permalink) Old Jun 19th, 03, 10:24 PM
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Talking

yeah, i figured thats what you meant dnult, just thought i'd clarify. hope i didn't come off as a jackass though [img]graemlins/clonk.gif[/img] let us know what you come up with '67rsss

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

Franklin D. Roosevelt
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post #9 of 12 (permalink) Old Jun 20th, 03, 05:05 AM Thread Starter
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Todd
 
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I took the car out last night to top off the gas tank and to see if it would make a 20 mile round trip without problems. Yea, I made it home without any problem, although I noticed it didn't run quite as well with the 92 octane gas I put in. Had Sunoco 115 racing fuel in it before the fill up. Anyway...I didn't get a chance to run a tester on the wire, but I did inspect it. Probably needs to be replaced. Lots of bad areas where there is exposed copper. It could have been shorting in several places when I hooked it up the last time when it started to smoke. I'm also assuming that because this wire is currently not hooked up, thats why my brake warning light is on.? I'll post again when I have a chance to test the wire.
Todd

Bolero Red/Black 67 rs/ss, 350 4-sp, Deluxe interior, slowly becoming a restomod
Aqua blue/White 77 LT Type, Built 305 auto, in the restomod process, wife's car since high school.
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post #10 of 12 (permalink) Old Jun 20th, 03, 12:03 PM
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One of the two circuits must be grounded to light the brake warning light - the one on the differential pressure valve or the emergency brake. Even if the wire was chafed and grounding out, all it should do is illuminate the light. The fact that it melted down is very strange.

-dnult

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #11 of 12 (permalink) Old Jun 24th, 03, 03:41 AM Thread Starter
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Todd
 
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OK, with the ignition switch on, the tan wire that runs out to the pressure switch on the master cylinder is running 12v. Ignition switch off, no voltage. I plugged it in last night and the light didn't go off. So then I started the car up and let it idle a bit, felt the wire and it wasn't hot, but light remained on.???? Back to the emergency brake switch.

Here's another one. I've been trying to figure out why my interior lights won't come on. I've traced voltage back to the courtesy light by the ashtray on the rear of the console. I have 12 volts all the way to the posts that hold the bulb. With the bulb out of the posts, I have 12v to both posts. Is this right? I put brand new bulbs in and get no light. I put brand new bulbs in the sail panel lights and nothing. The wiring looms in this car are all stock, nothings been butchered. This electrical stuff can be maddening! Any more suggestions here would be very helpful and much appreciated.

Thanks, Todd

Bolero Red/Black 67 rs/ss, 350 4-sp, Deluxe interior, slowly becoming a restomod
Aqua blue/White 77 LT Type, Built 305 auto, in the restomod process, wife's car since high school.
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post #12 of 12 (permalink) Old Jun 24th, 03, 11:02 AM
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“OK, with the ignition switch on, the tan wire that runs out to the pressure switch on the master cylinder is running 12v.”

That’s a normal reading with the tan wire removed from the pressure switch and the e-brake switch off. If the e-brake switch is working the light should go off and on with the e-brake, IF you leave the tan wire disconnected under the hood. Still sounds like a problem with the front pressure switch. If you leave the wire off of it, measure the pressure switch contact to its body with a meter. The contact should show it’s shorted to the body. Normal reading is an open circuit.

“Here's another one. I've been trying to figure out why my interior lights won't come on. I've traced voltage back to the courtesy light by the ashtray on the rear of the console. I have 12 volts all the way to the posts that hold the bulb.”

There is always 12 volts to the courtesy lamps. They operate by switching the ground wire. Just like the brake light above, you will see 12 volts on the ground side bulb as long as:
1, The ground side of the lamp isn’t grounded.
2, You have a lamp or lamps installed in the circuit.
Voltage is visible because it comes through the lamp filament when the filament isn’t grounded.
Try grounding the white wire on the passenger door switch and see what happens.
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