Fusible Link and Electrical Woes

[69sroadster]

So I thought my car was acting a little funny the last few days of driving, but it wasn't until today that it seemed to be really noticeable.  The battery turning the motor over seemed like it was getting low on juice and only turning it over slowly.  Once it fired up it was fine.  I thought that was weird until when I shut it down.  It seemed like the voltage gauge went down initially, then bounced for a bit and then went back up to 12v.  I thought that was weird and that it was supposed to normally go back to the zero mark with the keys out and completely locked steering.  So I put the keys back in and turned the ignition switch a few times from locked/off to run.  It seemed like it was staying on when it should be off.  I had to run into work so I left it alone.  At the end of the day I came back and noticed the same thing basically.  I drove all the way back home and parked it.  Once there I started checking around for the usual suspects.  Battery cables are good.  No obvious ground on any big wires under the hood area.  Voltmeter on the battery showed a good 12v.  I pulled the fusible link cover off to inspect and I notice that the "B" labeled one going to the ACC/IGN (closest to the engine under the cover) was charred and barely touching the post.  Hmm...it looks like it was trying to protect against something but what?  I started the car (barely) with it off the post.  Everything seemed to work fine too.  I temporarily connect it back and yep, it's getting pretty hot.  I can tell its loading down the alternator and pushing a lot of current through there.  Oddly, I also see that my voltage in the car is reading 14.5 v with this fusible link disconnected.  Is there another way for that voltage to get to the gauge without the fusible link connected?  I'll have to really scour the wiring diagram to find out.  It got dark before I could really tear into this, so I'll have to do some more digging.  I don't suspect the alternator since it's giving a good 14.5v at least to the gauge.  Is this a bad assumption?  I want to figure out what could be shorting that would act so weird like this, but still let the car run or even start.  The only other clue I seem to have is a quiet but high pitched tone near the radio area that I don't recall being there before.  Everything in that area seems to work for now and I didn't do any work there.  I'm going to have to start from the basics with my voltmeter shooting for continuity/grounds starting at the alternator and working to the starter and ignition. 

 

I hate that this had to happen this week with my alignment scheduled for tomorrow that is holding up my new registration here.  Maybe after this is all straightened out I can get back to the suspension write-up for going to the TTT front. 

[NewZed]

There are two functions combined in the alternator -  production and regulation.  You might have a regulator problem.  Could be shorting.

[69sroadster]

Aw man has this been frustrating.  So I disconnected the alternator and shot a short test against the two output posts and they both showed some grounding to the casing.  I also shot the wires themselves after disconnecting them and the blue wire going to the loom was showing a short.  Digging deeper I found a short in the yellow feed wire to the starter.  I disconnected it and it showed a short on the little wire going to the starter solenoid, so I guess that's bad too now.  I tested the fusible link box for a short and it initially had one until I disconnected the alternator.  I went inside the car and pulled the fuse block off the sidewall to shoot wires too.  Most of those are showing a short somewhere.  I disconnected the ignition/accessory relay harness and three of those wires are shorted somewhere (WB, WL and BW).  I think I need to re-test those after the sequence of disconnecting other components.  The fat white wire going to the blower across the fuse was showing a short/ground.  One of the blue wires from the EFI relay was showing a short.  This is going to be a real pain!  It's like there are shorts everywhere and I find that hard to believe.  Maybe more likely that some one interconnected component is affecting a lot of feeds, but I can't seem to figure out how/where.  So frustrating.  Oh yeah, the main battery cable is fine with no shorts.  I'm tempted to just replace the starter solenoid and alternator, hook it all back up and see what that shows without running the car yet.  In the back of my mind I'm thinking that somehow a relay is stuck closed.  The car was running fine but was turning over a bit slowly the last few times before this all shook down.  The battery was showing a good 12v before turning it over.  Once it started it was showing 14v on the dash meter.  Everything was working just fine.  There was one or two times the voltage before starting acted weird.  I have to think back about what it was doing with the voltage, gauges, lights  etc.  Almost like it was not all there until it was fired up and then it seemed to be okay.  I'm taking a break for now since I seem to be making less progress other than the solenoid and alternator shorts.  Time to sleep.

[69sroadster]

A lot has happened since this initial problem.  I'm not sure what started the mess but I'm guessing it was a combination of the starter solenoid and the alternator diodes going out.  The alternator was grounding out through the case.  It must have also been putting out some bad/dirty power since a lot of other components have been shorted out.  In the end I've had to systematically pull every single relay, switch, motor, light off the harness and test for improper grounding.  I've learned my JDM version S130 has a few differences from the USDM versions and repair manual...things not on the wiring diagram or different color schemes etc.  That has made it a bit more challenging.  So far here is what I've found also bad:  horns, intermittent wiper controller, under seat belt chime, some random green relay under the seat labeled "switching unit" that nobody has in Australian/Canadian/American models.  I also found the rear defogger timer (not in USDM manual) when connected pulls a short to the fuse block but it's not the timer rather something that is fed by it.  I can't find out what else it's connected to from under the seat and going to the back besides the grid which is fine.  I'm slowly putting it all back together one item at a time to make sure no other new shorts come back on the harnesses.  I also found that ALL of the pedal switch grommets are gone and were leaving the plunger switches open for the brakes/clutch.  I fixed those with some simple pennies and glue LOL.  The battery seemed like it didn't have one electron left when I hit it with the voltmeter so I will likely have to get a new one of those after the abuse it saw.  It's all slowly coming back together.  Anyone have an intermittent wiper controller/timer they can sell me?  Thanks for reading and hopefully I can help some others in the future when they get electrical trouble.  It's a long tedious process but can be figured out.  Oh and does anyone have a schematic for the wiring on the rear defogger timer?

[turbogrill]

Been a long time but did you manage to sort everything out?

I am currently fixing a broken electrical system on a 1980 280zx, I know the feeling

 

Sounds a little weird that you have all those things broken. Are you sure all your fusable links are good? Even if they look fine they can be broken inside, that happened to me.

 

How do you measure "pulls a short"? 

 

The paper version of the FSM has a nice schematic of everything.