High Beam Switch Killed Car - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 41 (permalink) Old Jul 8th, 18, 8:45 PM Thread Starter
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High Beam Switch Killed Car

Hello, I have a 1967 Chevelle and I was driving home and as soon as I pressed the floor high beam switch the entire car died. Everything electrical inside the car just shut off even the dome light. I didn't have a test light to see where the power was stopped at but I shook some wires going into the right side of the fuse panel inside the car and once I saw the dome light come on I knew I was good to go. I tried to make the car turn off by pressing the switch and shaking the wires but it didn't. I took the fuse panel off and everything was on, nothing loose or badly corroded. The car never did this before and how could the entire car lose power from turning on the high beams??
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post #2 of 41 (permalink) Old Jul 8th, 18, 9:29 PM
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Re: High Beam Switch Killed Car

A common issue is the main power connection going through the bulkhead connector on the firewall. By pressing the headlight switch you may have pushed the limit of a corroded terminal past what it could do by pulling a higher amount of amperage from the headlights now needing more power for the high beam than it did when just the low beams were on or possibly when pushing the dimmer the switch moved it's wires and then it moved some wires close to the bulkhead.

Jim
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post #3 of 41 (permalink) Old Jul 8th, 18, 10:15 PM Thread Starter
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Re: High Beam Switch Killed Car

I just checked the voltage drop. At the battery and firewall connector the voltage is 12.56. The the power wire connecting to the back of the fuse panel is 12.10. What is the reason for this big voltage drop? For the wire connecting to the fuse panel to be at 12.10 there has to be something corroded I would think. I have a wiring diagram and I cleaned all the grounds etc. The high beams definitely draw a lot of power because the voltage is only 13.5 volts in the car with it running but 14 volts at the battery etc. Once I turn on the high beams it drops to about 11 volts so I'm wondering if my alternator is too weak maybe?
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post #4 of 41 (permalink) Old Jul 8th, 18, 10:20 PM Thread Starter
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Re: High Beam Switch Killed Car

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Originally Posted by Jim Streib View Post
A common issue is the main power connection going through the bulkhead connector on the firewall. By pressing the headlight switch you may have pushed the limit of a corroded terminal past what it could do by pulling a higher amount of amperage from the headlights now needing more power for the high beam than it did when just the low beams were on or possibly when pushing the dimmer the switch moved it's wires and then it moved some wires close to the bulkhead.

Jim
So why would the entire car lose electrical power? I would've thought that the dome light or something not needing much electrical current would still work t least. Wow.
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post #5 of 41 (permalink) Old Jul 8th, 18, 10:34 PM
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Re: High Beam Switch Killed Car

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Originally Posted by JROCK142 View Post
I just checked the voltage drop. At the battery and firewall connector the voltage is 12.56. The the power wire connecting to the back of the fuse panel is 12.10. What is the reason for this big voltage drop? For the wire connecting to the fuse panel to be at 12.10 there has to be something corroded I would think. I have a wiring diagram and I cleaned all the grounds etc. The high beams definitely draw a lot of power because the voltage is only 13.5 volts in the car with it running but 14 volts at the battery etc. Once I turn on the high beams it drops to about 11 volts so I'm wondering if my alternator is too weak maybe?
You already have your answer, the bulkhead connector is the problem. 12 gauge red wire from the horn relay feeds all power for lights, ignition, accessories thru the bulkhead connector. Pull the connector loose on the engine side of the firewall and check for corrosion. Very common problem on these 50 year-old cars.
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post #6 of 41 (permalink) Old Jul 8th, 18, 10:46 PM
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Re: High Beam Switch Killed Car

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Originally Posted by JROCK142 View Post
So why would the entire car lose electrical power? I would've thought that the dome light or something not needing much electrical current would still work t least. Wow.
On my 68 Chevy II Nova, there is one 12 gauge wire going to a terminal in a plug with other wires on the engine side of the bulkhead connector and this is my main and ONLY feed to the electronics past it inside the car. Chances are yours is laid out about the same. On the the mating part of this bulkhead connector bolted to the firewall and between the backside of the fuse block and the firewall is another connector that then get's split with 12V going to different thinks like the ignition switch, the headlight switch, and the fuse block.

When troubleshooting you need to know exactly what is or is not working and then start looking for commonality between those things. For example if just the headlights quit working but the dome light still worked and the car still ran, then the main power into the car from the bulkhead is probably good but the issue with just the headlights going off would be a problem with that circuit. It as well as the ignition and fuse block get power from the same main line into the car but if those are working then the headlight issue is not a problem with an ignition switch for example or a fuse block issue.

Look at things in your house, if the power coming into the house went out due to a connection opening up off of the pole in the street, not even an alarm clock would work but if while at home the fridge quit working but the lights in the room worked, you might have an issue just with that circuit for the fridge and not main power coming into the house.

Keep in mind that when current flows heat also increases and if you had a marginal connection on a bulkhead connector it might be good enough to allow the car to run as it might only require a few amps to power the ignition system but then turn on the headlights and now the amperage jumps another 10A and now that marginal connection heats up more and if this connection is in a plastic housing, the connector may spread apart just enough to stop the flow of power. Now with no power passing through this marginal connection it cools and may reconnect itself poorly once again allowing you do go down the road once again.

Touching back on commonality, if my car were to shut off and the dome light and headlights would not work I would then try the horn. How my car is wired is, if the horn did work then I would be looking at connections past the horn relay under the hood to and through the bulkhead connector and then into the car BUT if the horn didn't work also, then I would be looking for issues between it and the battery positive post.

Jim

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post #7 of 41 (permalink) Old Jul 8th, 18, 10:53 PM Thread Starter
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Re: High Beam Switch Killed Car

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Originally Posted by pnugene View Post
You already have your answer, the bulkhead connector is the problem. 12 gauge red wire from the horn relay feeds all power for lights, ignition, accessories thru the bulkhead connector. Pull the connector loose on the engine side of the firewall and check for corrosion. Very common problem on these 50 year-old cars.
It's crazy, I pulled the connector off and checked the power which is the same as the battery and the connector looks the same as the wire from inside of the car. The wire coming from inside the car is not corroded, the fuse clips look worse than the connector if anything else. I used steel wool and everything to clean the bulkhead connector and it's the same. I'll have to look at the wiring diagram again to see where the main power wire goes before it gets tot he fuse panel or soemthing
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post #8 of 41 (permalink) Old Jul 8th, 18, 10:57 PM Thread Starter
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Re: High Beam Switch Killed Car

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Originally Posted by Jim Streib View Post
On my 68 Chevy II Nova, there is one 12 gauge wire going to a terminal in a plug with other wires on the engine side of the bulkhead connector and this is my main and ONLY feed to the electronics past it inside the car. Chances are yours is laid out about the same. On the the mating part of this bulkhead connector bolted to the firewall and between the backside of the fuse block and the firewall is another connector that then get's split with 12V going to different thinks like the ignition switch, the headlight switch, and the fuse block.

When troubleshooting you need to know exactly what is or is not working and then start looking for commonality between those things. For example if just the headlights quit working but the dome light still worked and the car still ran, then the main power into the car from the bulkhead is probably good but the issue with just the headlights going off would be a problem with that circuit. It as well as the ignition and fuse block get power from the same main line into the car but if those are working then the headlight issue is not a problem with an ignition switch for example or a fuse block issue.

Look at things in your house, if the power coming into the house went out due to a connection opening up off of the pole in the street, not even an alarm clock would work but if while at home the fridge quit working but the lights in the room worked, you might have an issue just with that circuit for the fridge and not main power coming into the house.

Keep in mind that when current flows heat also increases and if you had a marginal connection on a bulkhead connector it might be good enough to allow the car to run as it might only require a few amps to power the ignition system but then turn on the headlights and now the amperage jumps another 10A and now that marginal connection heats up more and if this connection is in a plastic housing, the connector may spread apart just enough to stop the flow of power. Now with no power passing through this marginal connection it cools and may reconnect itself poorly once again allowing you do go down the road once again.

Touching back on commonality, if my car were to shut off and the dome light and headlights would not work I would then try the horn. How my car is wired is, if the horn did work then I would be looking at connections past the horn relay under the hood to and through the bulkhead connector and then into the car BUT if the horn didn't work also, then I would be looking for issues between it and the battery positive post.

Jim
I wanted to know where the power stopped but I didn't have a test light when the car stopped on the road. It had to of been before the firewall because if the dome light and everything else in the car didn't work then its not power at the bulkhead connector. I should've tried the horn but I didn't. At first I thought the bulkhead connector came off or was loose but it was connected tight.
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post #9 of 41 (permalink) Old Jul 8th, 18, 11:02 PM
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Re: High Beam Switch Killed Car

Jordan, not to beat the horse here, but did you inspect & clean both halves of the bulkhead connector, i.e. firewall side & interior side? The voltage drop you're seeing is your clue to the problem.

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post #10 of 41 (permalink) Old Jul 8th, 18, 11:28 PM
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Re: High Beam Switch Killed Car

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Originally Posted by JROCK142 View Post
I wanted to know where the power stopped but I didn't have a test light when the car stopped on the road. It had to of been before the firewall because if the dome light and everything else in the car didn't work then its not power at the bulkhead connector. I should've tried the horn but I didn't. At first I thought the bulkhead connector came off or was loose but it was connected tight.
I know how it is without having the proper tools to try and figure things out but a short story is years ago I was going out of town with a car at night and it broke a bracket for the alternator to where the belt became loose and the further I drove, the less the alternator could keep up and the headlights kept getting dimmer and dimmer so I pulled over to figure things out. I got under the hood and with a bic lighter lit up the area and saw the issue and then came up with a plan to get me back on the road.

I did not have a test light or any handy light to let me see what I was doing to fix the problem but I did have some speakers in the car wired to the stereo so I pulled them out. I then had some electrical tape and then pulled out a taillight bulb and after stripping the wires with my teeth taped the wire ends to the bulb and then once under the hood, attached them to the battery. I then had an underhood light to see what I was doing. Things were going smooth and all of a sudden I noticed headlights shining on me and I turn around at it's one of Missouri's finest state patrol officer's and he rolls his window down and is chuckling seeing my "rig" with the light and asks if I'm all right. I tell him I think I got it and he says good luck and he will be by later and if I need, he can give me a ride into town. I was able to get some tension on the alternator belt and then pushed the car to a hill and coasted down it and pop started it and drove on the rest of the way to my destination. I was out in the middle of no where and had to become a Mcgyver.

Now in my road trip bag I have a test light, a flashlight, some scrap wire, wire strippers, tape, and some other things as you never know sometimes.

Jim
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post #11 of 41 (permalink) Old Jul 8th, 18, 11:52 PM Thread Starter
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Quote:
Originally Posted by pnugene View Post
Jordan, not to beat the horse here, but did you inspect & clean both halves of the bulkhead connector, i.e. firewall side & interior side? The voltage drop you're seeing is your clue to the problem.
Yes, both sides.
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post #12 of 41 (permalink) Old Jul 9th, 18, 12:01 AM Thread Starter
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Quote:
Originally Posted by JROCK142 View Post
I wanted to know where the power stopped but I didn't have a test light when the car stopped on the road. It had to of been before the firewall because if the dome light and everything else in the car didn't work then its not power at the bulkhead connector. I should've tried the horn but I didn't. At first I thought the bulkhead connector came off or was loose but it was connected tight.
I know how it is without having the proper tools to try and figure things out but a short story is years ago I was going out of town with a car at night and it broke a bracket for the alternator to where the belt became loose and the further I drove, the less the alternator could keep up and the headlights kept getting dimmer and dimmer so I pulled over to figure things out. I got under the hood and with a bic lighter lit up the area and saw the issue and then came up with a plan to get me back on the road.

I did not have a test light or any handy light to let me see what I was doing to fix the problem but I did have some speakers in the car wired to the stereo so I pulled them out. I then had some electrical tape and then pulled out a taillight bulb and after stripping the wires with my teeth taped the wire ends to the bulb and then once under the hood, attached them to the battery. I then had an underhood light to see what I was doing. Things were going smooth and all of a sudden I noticed headlights shining on me and I turn around at it's one of Missouri's finest state patrol officer's and he rolls his window down and is chuckling seeing my "rig" with the light and asks if I'm all right. I tell him I think I got it and he says good luck and he will be by later and if I need, he can give me a ride into town. I was able to get some tension on the alternator belt and then pushed the car to a hill and coasted down it and pop started it and drove on the rest of the way to my destination. I was out in the middle of no where and had to become a Mcgyver.

Now in my road trip bag I have a test light, a flashlight, some scrap wire, wire strippers, tape, and some other things as you never know sometimes.

Jim
Very cool, that was some smart thinking there! I had that happen about a year ago and I used a tree branch ina local parking lot which allowed me to get tension on that alt belt. I had everything in my tool bag (at least I thought) besides a test light but it’s in there now I can tell you that. I might change that wiring harness inside the car to be honest.
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post #13 of 41 (permalink) Old Jul 9th, 18, 5:34 AM
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Re: High Beam Switch Killed Car

Jim,
I don't agree with your reasoning of the corroded connector terminals causing the problem.

It sounds like when the OP pressed the dimmer sw, he got a dead short, & that is what killed the engine.[ Battery voltage was pulled down to a level that the ign stopped working ]

Corroded terminals increase circuit resistance, which reduces, not increases, current, so I don't see how this could be the problem.
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post #14 of 41 (permalink) Old Jul 9th, 18, 11:29 AM
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Re: High Beam Switch Killed Car

1 wire has everything in common, ground...
Did the engine actually shut off when this happened?

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post #15 of 41 (permalink) Old Jul 9th, 18, 12:09 PM
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Re: High Beam Switch Killed Car

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Originally Posted by Gtogeoff View Post
Jim,
I don't agree with your reasoning of the corroded connector terminals causing the problem.

It sounds like when the OP pressed the dimmer sw, he got a dead short, & that is what killed the engine.[ Battery voltage was pulled down to a level that the ign stopped working ]

Corroded terminals increase circuit resistance, which reduces, not increases, current, so I don't see how this could be the problem.
A bad connection can completely disconnect the feed circuit when put under load.
Resistance causes voltage drop and it can drop to zero.
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