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I have a self inflicted electrical problem, this is a stock 65 L79 with a new engine wiring harness last year due to some bad wires. I noticed a small amount of battery terminal corrosion last week so I got a small brass bristled toothbrush to remove it. While brushing the positive terminal I accidentally touched the battery hold down frame which caused a brief spark/sizzle. I stopped and looked inside the car, my clock and courtesy lights still worked so I thought there was not a problem. Fast forward to Sunday when we decided to go for a ride....I turned the key and heard a click and nothing else. I released the key and tried another time, this time no click or anything and I lost all power, no clock, no courtesy lights, nothing.
I have been following the power on the wiring diagram, I have 12v at the battery, at the horn relay, the alternator and the red wire at the firewall connector, actually, 3 wires at the firewall connector. I can't find any power inside the car anywhere. I have not been under the car yet to look at the wires at the starter.
If you have 12v at the red wire on the firewall you should also have it inside the cabin. The red wire goes through the firewall connector (both sidesof the same connector) to the cigarette lighter, the headlight motor circuit breaker and the bottom two fuses in the fuse box (left side). Check to see if you have 12v at any of those places in the cabin and post back. You could have a loose or corroded connection on the other side of the connector at the firewall, or a burned wire inside the cabin, though not likely a spark would burn a wire. If you will tell me if you have voltage at one of these three places, I think we can track it down.
PS, it also feeds the 12v to the ignition switch red wire.
Last edited by 65GGvert; Jun 21, 2016 at 10:27 PM.
The battery terminals and posts are clean and tight, no sign of any corrosion. I have power at the outside firewall plug, but nothing inside at all, no power anywhere mentioned above. I started wiggling connections with no change then I noticed the circuit breaker on the side panel. I started loosening the nuts and took one wire off and all of a sudden the 12v came alive inside the cabin. I reattached the wire that I had removed, then I tried to start it and had the same result, click and then all 12v power is gone again. I repeated this one more time with the same result, now no matter what I do I can't get the power back inside the cabin. I poked around in every connection that I can see up there.
It seems like a bad connection or bad ground, but why does the process of starting the engine cause it to lose power? What is the purpose of the circuit breaker?
The battery terminals and posts are clean and tight, no sign of any corrosion. I have power at the outside firewall plug, but nothing inside at all, no power anywhere mentioned above. I started wiggling connections with no change then I noticed the circuit breaker on the side panel. I started loosening the nuts and took one wire off and all of a sudden the 12v came alive inside the cabin. I reattached the wire that I had removed, then I tried to start it and had the same result, click and then all 12v power is gone again. I repeated this one more time with the same result, now no matter what I do I can't get the power back inside the cabin. I poked around in every connection that I can see up there.
It seems like a bad connection or bad ground, but why does the process of starting the engine cause it to lose power? What is the purpose of the circuit breaker?
You have a bad connection either on the firewall side connector or on the wire from there to the back side of the fuse box. You may have to drop the fuse box if you have 12v on the red wire on the firewall side of the connector, but not on the left side of the two bottom fuses in the panel. My first step would be to disconnect the connector on the firewall and take a look at the pins. I think you'll either see corrosion, or the pin will be pushed back in the connector so it's barely making contact. If you're adventurous, you can use a jumper from the 12v on the engine side and connect it to the hot side of that headlamp motor circuit breaker you found or to the left side of the bottom fuse. The 12v should come on in the cabin. You are in the right area, you just haven't located the open circuit due to corrosion or a loose connection. It will be between the fuse panel and the connector that stays in the firewall when you disconnect the engine side of it.
You have a bad connection either on the firewall side connector or on the wire from there to the back side of the fuse box. You may have to drop the fuse box if you have 12v on the red wire on the firewall side of the connector, but not on the left side of the two bottom fuses in the panel. My first step would be to disconnect the connector on the firewall and take a look at the pins. I think you'll either see corrosion, or the pin will be pushed back in the connector so it's barely making contact. If you're adventurous, you can use a jumper from the 12v on the engine side and connect it to the hot side of that headlamp motor circuit breaker you found or to the left side of the bottom fuse. The 12v should come on in the cabin. You are in the right area, you just haven't located the open circuit due to corrosion or a loose connection. It will be between the fuse panel and the connector that stays in the firewall when you disconnect the engine side of it.
The wiring harness is new so the connector on it is good, I unplugged it and looked at the mating plugs on the firewall and they look good, no corrosion or out of place. Which side of the circuit breaker is the hot side?
That circuit breaker is only for the headlamp motors, so I doubt it has anything to do with your problem. There is no way to check which is the hot side except to remove one terminal and check for voltage. Careful, it is live all the time.
If I were you, I would:
Disconnect the battery.
Remove the bottom fuse so you can access one of the 2 screws holding the fuse box to the firewall connector.
Remove both screws and pull the fuse box away from the firewall connector.
Take some pictures and post them up here.
The wiring harness is new so the connector on it is good, I unplugged it and looked at the mating plugs on the firewall and they look good, no corrosion or out of place. Which side of the circuit breaker is the hot side?
If the breaker is good, both sides are hot. It doesn't matter which side you connect to. If your fuse box and wiring are new, you have a broken wire or loose connection in that area. Once the 12v gets to the firewall connector, it goes directly to the connections on the back of the fuse panel.
Last edited by 65GGvert; Jun 23, 2016 at 07:24 AM.
Ok, I finally got to spend a little time on the car today. I tried to drop the fuse box, removed the fuses and the 2 screws and was able to pull it down a little bit and separate the two halves a little bit but there are 4 or 5 wires that run down out of there under the carpet that prevent me from completely separating it. I did some more checking with my meter, here is what I see:
12 volts at the pin going into the bulkhead connector:
Continuity from the mating plug to the fuses inside:
But then when I connect the cable to the connector, almost no voltage inside:
The wires running down under the carpet go to the dimmer switch. Just pull back the carpet and pull the connector off.
You really need to check the voltage at the 'Bat-Power Window' terminal as I showed in post #8. It is a direct connection to the connector on the engine side of the firewall where you found full voltage.
Same advice as before. You have no connection between the pin you have the green wire attached to to check continuity and the fuse box. Those pins on the firewall look pretty corroded. Connect a jumper from the side of the connector where you have 12v to the pin you have the green wire on. See if you get power inside. Do that first. Post back.
The next most likely is the connections on the back of the fuse panel. Your problem has to be there (if you're getting a good ground connection on your meter in the picture you show measuring on the fuse box). Look at the diagram I posted, it's a straight shot.
Same advice as before. You have no connection between the pin you have the green wire attached to to check continuity and the fuse box. Those pins on the firewall look pretty corroded. Connect a jumper from the side of the connector where you have 12v to the pin you have the green wire on. See if you get power inside. Do that first. Post back.
The next most likely is the connections on the back of the fuse panel. Your problem has to be there (if you're getting a good ground connection on your meter in the picture you show measuring on the fuse box). Look at the diagram I posted, it's a straight shot.
Ok, I put the jumper between the connector pin with the 12V to the firewall pin and still no power inside. I then dropped the fuse panel:
Then I ran the same jumper from the connector pin with the 12v to the firewall pin (now inside the car) and I have 12v at the appropriate points. I had to remove the bottom fuse to take the bolt out to drop the fuse panel, so these readings were done with the fuse removed. I then put the fuse back in and all power is gone again. I can put my meter on the back side of the firewall pin with the fuse out and see 12 v and swing the fuse back in and see it go away.
Reconnect your firewall connector and measure at the points where I've put an arrow. The top two arrows show where the 12v should come in and then split to the "bat" connection, the others show where it should be distributed to the fuse panel. I suspect the pin with the split red wire at the bottom.
Reconnect your firewall connector and measure at the points where I've put an arrow. The top two arrows show where the 12v should come in and then split to the "bat" connection, the others show where it should be distributed to the fuse panel. I suspect the pin with the split red wire at the bottom.
What arrows are you talking about? The ones on the wiring diagram?
What arrows are you talking about? The ones on the wiring diagram?
Sorry, I forgot to attach the picture. I suspect you'll find a corroded or loose connection where the two red wires go to the left hand side of the stop fuse, shown in the lower right-
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Electrical problem
