Reversed polarity

[Viking78Z]

Hey guys, I know there might already be a forum about this but I haven't been able to locate it myself. I accidentally hooked a jumper box into my 1978 280z backwards and now the fuel pump as well as the dummy light for the alternator both stay on when the battery is connected. I thought it could be a fried ignition switch but even when I unplugged it they both stayed on. The car fires up and idles perfectly. If anyone could help me out I'd really appreciate it. 

[Zed Head]

Did everything work correctly before?  Is connecting the jumper box absolutely the only thing that you did?  No other things that "couldn't possibly be" part of the problem.

Seems like you might have short-circuited something in the pump power control relay, it uses the alternator charge circuit as a control mechanism.  You could try unplugging it and see what happens.

I think that the relay is behind the metal box by the battery.  You'll have to figure out this picture yourself.

 

 

 

[Viking78Z]

I disconnected that and it stopped the pump from going on but the interior dummy light still came on. I know my volt meter fuse keeps blowing for some reason. It works for like 3 minutes and then popps

[Zed Head]

13 minutes ago, Viking78Z said:

I know my volt meter fuse keeps blowing for some reason. It works for like 3 minutes and then popps

I knew that there would be more clues.  I would sit down with the FSM and look at wiring diagrams.  And put the clues together.  Does the Charge light (that's what most call it, not a dummy light) go out when the fuse blows?  Does the pump stop?

[Viking78Z]

Charge light always works when the meter doesn't. The fuse blows and just takes out the meter itself. It's the fuse that's on the right hand side third fuse up

[Zed Head]

18 minutes ago, Zed Head said:

  Does the pump stop?

Hate to badger you.  But if you can put all of the small details together you'll have a better chance.  Your problem is uncommon.  Doubtful that anyone will have a "that happened to me" answer.  You never know though.

I'm going to guess that something has shorted in the voltmeter and and is somehow powering the pump power control relay and the Charge lamp.  Not sure how that would actually work, it's a puzzle that my brain doesn't want to work on.  Does the meter smell like burnt wires?

Try unplugging the voltmeter.  That might fix everything, except you won't have a meter or a Charge lamp.  You'll have to take the meter out, it's pretty easy.  It comes out from the back.  Described in the FSM.  If you have dexterous fingers you might get it unplugged with just removing the front panel.
 

[PastorKB]

I just so happen to have avery simular situation going on with my z as well. A little late tonight to get into it , but ill be back tomorrow and perhaps we can figure it out

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[riverstonefly]

Hate to badger you.  But if you can put all of the small details together you'll have a better chance.  Your problem is uncommon.  Doubtful that anyone will have a "that happened to me" answer.  You never know though.
I'm going to guess that something has shorted in the voltmeter and and is somehow powering the pump power control relay and the Charge lamp.  Not sure how that would actually work, it's a puzzle that my brain doesn't want to work on.  Does the meter smell like burnt wires?
Try unplugging the voltmeter.  That might fix everything, except you won't have a meter or a Charge lamp.  You'll have to take the meter out, it's pretty easy.  It comes out from the back.  Described in the FSM.  If you have dexterous fingers you might get it unplugged with just removing the front panel.
 

I concur with this assessment! Sorry but I have to ask....how does one connect a jumper box or cables in reverse [emoji19] the cables are colored red and black....[emoji16] And the terminals are clearly marked.

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[psdenno]

8 hours ago, riverstonefly said:

Sorry but I have to ask....how does one connect a jumper box or cables in reverse the cables are colored red and black.... And the terminals are clearly marked.
 

Murphy's Law

https://en.wikipedia.org/wiki/Murphy's_law