Alternator not powering battery

[Zed Head]

And I'm pretty sure the externally regulated alternators all have a plastic assembly on the back.  Like this.  Yours doesn't. Just looks like the wrong unit.

[jlenownnab]

It wouldn't shock me if Orielys gave me the wrong part. He has been 20 years at big Toyota dealership, he's good. He is just trying to learn the wiring diagram and make sense of an old car. thankyou for your help.

[Zed Head]

2016 - 20 = 1996.  They stopped using external regulators in 1978.  He may not be familiar with how they work.  The "Signal" wire would be going to the regulator, not the alternator.  Sounds like he's trying to rationalize how they work, but that will be difficult.  Just saying, he might be trying but these old cars can be tricky.  Check the Download section of the forum for Service Manuals and diagrams.

Anyway, I think that Oreilly gave you the wrong alternator and when you get the right one you'll probably be fine.

 

[jlenownnab]

yep, he will agree with you. He is a master with Miatas. I will go over this post with him, it's probably the wrong alt though. Thanks

[Zed Head]

Tell him that original external regulator use mechanical points like an old distributor and see what he says (your replacement might be solid state though).  There's actually a procedure for adjusting them.  Shown in the Engine Electrical chapter of the factory FSM.  Good luck.

[jlenownnab]

any idea why tach isn't working??

[Zed Head]

The tachs do go bad sometimes.

Since you're here you might as well give the whole story of when the alternator went bad, when the tach went bad, what you were doing when it(they), any early signs that you saw, etc.  The problems could be related or not.  Does the car drive now, after you charge the battery?  Or has it been sitting?

As siteunseen said, fuses can go bad, along with fusible links and relays.  These cars are old, and they tend to leak.  The electrical tend to corrode and rust.  With more details something might show.

[Zed Head]

The tachs do go bad sometimes.

Since you're here you might as well give the whole story of when the alternator went bad, when the tach went bad, what you were doing when it (they) died, any early signs that you saw, etc.  The problems could be related or not.  Does the car drive now, after you charge the battery?  Or has it been sitting?

As siteunseen said, fuses can go bad, along with fusible links and relays.  These cars are old, and they leak.  The electricals tend to corrode and rust.  With more details something might show.

Edited July 1, 2016 by Zed Head

[jlenownnab]

I just bought this car out of Dallas off Ebay. It is a one owner 70k garage kept, no rust all original car. It was on Ebay in late march early April from Texas Classic Cars (Thieves). They showed it in front of an airplane. The car came off the transporter barely running. So far I have fixed 3 fuel line leaks, alt, bat, volt reg and I have a car that still doesn't run. The tach lays all the way dead. The fuel gauge doen't work and it has a vacuum leak I have to find. But, low and behold the clock works, so I have that going for me. Can the tach problem be related to the distributer? And yes.... I probably paid to much for it with said problems.

[jlenownnab]

Yes, the car drives when battery is charged despite the vacuum leak.

[Zed Head]

A picture of the engine from the driver's side might show something.  Is the distributor not a stock 1975 distributor?  The tach is run from the blue wire from the negative post of the coil.  But there are many many ways to install a new ignition system so the tach may not even connected.

The engines are very durable so the fact that yours runs means that with some work you'll probably get what you expected when you bought it.

If you know how to use a multimeter you might be better off in the long run fixing things yourself.  The cars are a complicated collection of simple parts.  With time most people make great progress.

[jlenownnab]

I will post more pics tomorrow, not exactly sure what I have.... I think its mostly original. I have come along way since I bought my 1970 4 yrs ago, but I still have not got a grip on the electrical. I am learning a lot tonight and understanding it better just talking with you, thanks.