Wiring issues

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86k5blzr

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I have a 86 k5 I got last year and have been chasing wiring problems since. When the headlights are off I have 12 volts but when I cut the lights on I drop to 6v and when park lights are on the brake lights light up.I have replaced the ignition switch,headlight switch and the headlight dimmer switch still no fix. I've read where it could be a bad ground, does anyone know where I should start?
 

Ricko1966

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Boy,that's not a very good introduction. I'm Rick nice to meet you,glad you could be here.
 

Ricko1966

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Do you have 12 volts when just the parking lights are on? Where are you reading 12volts at? Do the headlights come on and stay on or come on and then start to blink? Something to check make sure all dual element bulbs a single element bulbs are in the right sockets.
 

86k5blzr

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Do you have 12 volts when just the parking lights are on? Where are you reading 12volts at? Do the headlights come on and stay on or come on and then start to blink?
I have 12v when the park lights/headlights are off as soon as I cut either one of them on it drops to 6. I am getting 12 volts at the orange wire in the headlight wiring at the switch. The headlights aren't wired up currently when I bought the blazer the headlights were wired up through a toggle switch that was straightwired. Super confusing
 

Ricko1966

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I have 12v when the park lights/headlights are off as soon as I cut either one of them on it drops to 6. I am getting 12 volts at the orange wire in the headlight wiring at the switch. The headlights aren't wired up currently when I bought the blazer the headlights were wired up through a toggle switch that was straightwired. Super confusing
How are you checking voltage at the switch? Where are you placing the 2 ends of the meter. Again with the bulbs,wrong bulbs,in wrong sockets create weird problems. Lots of different weird problems. Also need to f8nd all original wires under the hood for lighting and make sure none are shorting to ground.
 

86k5blzr

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How are you checking voltage at the switch? Where are you placing the 2 ends of the meter. Again with the bulbs,wrong bulbs,in wrong sockets create weird problems. Lots of different weird problems. Also need to f8nd all original wires under the hood for lighting and make sure none are shorting to ground.
I'm putting the volt meter here but when I tuen on the headlight or park lights the fuse box drops and everything drops to 6 but when the lights are off its fine super wierd. OK thanks I will check those out for sure thanks!
How are you checking voltage at the switch? Where are you placing the 2 ends of the meter. Again with the bulbs,wrong bulbs,in wrong sockets create weird problems. Lots of different weird problems. Also need to f8nd all original wires under the hood for lighting and make sure none are shorting to ground.
 

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Ricko1966

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I'm putting the volt meter here but when I tuen on the headlight or park lights the fuse box drops and everything drops to 6 but when the lights are off its fine super wierd. OK thanks I will check those out for sure thanks!
Where are you placing EACH end of the meter?
 

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My thought was that if the battery was serviceable the voltage drop shouldn't go below 10.5 or thereabouts. 6 v is so far in the mud that it is either has a bad cell or is overall pile of scrap.

I could be wrong
 

Ricko1966

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My thought was that if the battery was serviceable the voltage drop shouldn't go below 10.5 or thereabouts. 6 v is so far in the mud that it is either has a bad cell or is overall pile of scrap.

I could be wrong
Yes but if he's got an insufficient connection that won't pull 12v through it he could drop 6 volts,he could drop 11 volts. But it can be measured and isolated with the meter. I'm at 6% charge I'm done for a while, maybe the night. But search our search engine I'm sure I put up a post on how to do volt drops to find bad connections,broken wires. Another quick example cause it's so basic and easy to understand,if I had a slow cranking starter,I could put 1 lead on the positive battery POST,not terminal, and 1 lead on the starter POST then if you engage the starter and the meter reads 4 volts the cable and all the connections can only carry 8.Now you need to clean all the connections maybe it's just a bad connection. Still got 4 ? Okay the crimped ends are corroded inside or the wire inside the jacket has broken several strands. Buy by providing a parallel path we can read on the meter how many volts we are dropping through the cables and connections. I believe it's supposed to be .1 volts loss per connection as spec, as long as I'm not seeing over .5 .75 volt I'm not going to get excited,but we might see 6 on one of his wires,that would be awesome,because would tell us,his wire and connections,could only support 6 volts. So we found the problem. I still want to know if the correct bulbs are in it though. front and rear because a single element in a dual element socket,even in the front can create a backfeed.
 
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