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way lost on electrical :(


tl154

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so have a strange issue. today firing up the z, ( 1981 280zx ) all hell broke loose.  it has been starting a little harder because of the colder weather, but thats normal for it.   but then all of the sudden i lost power to everything. no radio / heat/ lights / dash lights/ brakes / signals.  nothin at all.    the really wierd part is that every once in a while the voltage gauge pulses. between nothing to about 10 (white key at off/lock ) .

 

 

i havent really touched anything with it i know how touchy electrical can be.    currently it is doing this.   if you hit the brake. no lights,   voltage drops to nothing on the dash guage.   pretty much anything you do flat lines the volt gauge.   

 

i would guess a main fuse or does this car have one ?  if so where is it.    a bad relay maybe ?    im not sure where to set.  any help would be highly respected :)

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if this is any use the last few weeks it has been drawing way more power then normal if thats ant use i.e. when you use the brake the dash lights would dim by like 40% i would guess.    or if you turn the radio up it would click off ( its not some huge system with subs and all that   just 2 small speakers in the dash board )

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Fusable link... check em. 

 

Sounds like you have a bad ground. Could be putting additional load on other grounds. Not sure if the fusible links are on the positive or negative.. but this could cause one of them to burn up.

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Check the battery posts, unless you did it and trust your own work.

 

Now check the ground lug on the head and the positive lug on the starter.

 

There should be a solid ground from the negative post or cable to the body sheet metal.

 

Fusible look may look burnt or melted but test for continuity with a meter.

 

While you have the meter out check across the battery with (about 14.5volts) and without (12.5 volts or less) the engine running.

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This sounds stupid but it happened in 82 280zx. Somehow the connector on the ignition switch got bumped loose, I turned it off one night and nothing the next day. It took me embarrassingly long to figure it out. I doubt this is your problem, but just in case...

I never did figure out just how it got knocked loose.

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Check the battery terminals again.  I know you said you already checked them, but sometimes the connection can go bad, even on pjust worked on new battery cables.  Lead is used in the battery post, and in most terminals.  Bare clean lead oxides when exposed to oxygen in the air.  Any fumes from sulphuric acid in the area of the terminal only makes the problem worse.

 

Check the grounds.  Make sure the battery negative has a good clean connection to the engine.  Make sure both have a good connection to the body.

 

Turn on the headlights, and try to crank the engine.  If the headlights dim a lot, or go completely out, that is a big clue you have a bad connection to the battery.

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bat is good, posts are clean, terminals are clean. everything is tight.    bat tests at 12.64 off,  cannot test while the engine  is running right now. connections are greased to help with corrosion. testing bat at the end of each cable as well.

 

the negative cable has always been just one wire that connects on the starter. ( on the mounting ear ) it was replaced and put exatly the same way. i would think that would ground it just fine.

 

ignition switch connection is good, perfectly clean and tight.

 

all of the ohm readings for the fusible in the black box by the bat are good. ( im going to double check this tomorrow )

 

 

 

are there other fusibles to look for?   i have a wiring diagram but it is usless for me. everything is too small to read for me.   im looking for a blow up one right now.

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its just battery terminal grease.  100 % sure.       tests at 12.5   at the end of the pos cable and end of the neg cable

 

all of the fusible links are on the pos side.   the are each testing at .7 ohms  at the end of the links before it returns to the wiring.

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You are going to have to go thru everything again on the battery and the connections to the starter and block.

A bad connection on the pos/neg post of the battery will cause an issue like this, I can twist on the posts and get power back, but the moment I turn the key to start it, I lose everything, I twist the battery posts again and have power, hit the key to start it and lose everything again, that is what happens when you have a bad connection.

Pull the cables off the battery one at a time, place them back on and try to start it, if it doesn't change something go to the next post, once that is done, then go to the other ends of the cable, loosen and tighten the starter post nut, then the main ground cable to the engine, usually that would go to the engine block just above the alternator, but I am used to the L20b block.

Be careful when you check the starter post nut, it is hot all the time, it's best to disconnect the cable to the battery before touching that connection.

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still reading 12.5   v   from the bat positive post to:   block,   body  and negative post

 

 

the only damaged wire i have found so far is a black wire from the mount for the ignition cable to the bottom of the distributer.    i dont think its the problem but it needs replacing  non the less.  i might just get a whole new ignition coil all together  on account of its age.

 

 

could i be overlooking something as simple as the ignition switch ?   i dought i have tested that properly. 

 

thankyou for all the support this far.

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