Alternator not powering battery

[Zed Head]

15 hours ago, jlenownnab said:

The tach lays all the way dead. The fuel gauge doen't work 

Just pulling out some more clues.  Could be that the gauges have been out and didn't get reconnected.  

Also adding something for your mechanic.  Even though there may not be an actual charge light, the L(amp) wire is still the power supply for the alternator windings, I believe.  I assume that power comes in to the VR through L then goes out to F at the alternator.  Looks like Y gets its power from GR which comes from an ignition interlock unit.  Not familiar with that.  Made my head hurt just following the L wire out and I still don't know how it works.

Here's a full diagram - http://atlanticz.ca/zclub/techtips/wiringdiagrams/75_280z_wiring.pdf

[jlenownnab]

Thanks for video and everyones input. I thought i responded earlier and just saw that my response isn't up. I am meeting my mechanic in the morning Saturday. I am printing this post out for him, Although with all the good ideas I should be able to figure it out on my own. We checked fuses and found one blown.. clock/lighter. We did check fusable link for continuity, We did check signal wire while car was running and yes this car starts and runs good when operating off the battery despite the vacuum leak. I was only able to stop by my garage and snap a few pics today, here they are.

*IF IM NOT MISTAKEN, ORIELY'S HAS CAUSED ME A LOT OF GRIEF AND YOU GUYS UNNECCESSARY TIME SPENT HELPING*

WRONG ALTENATOR???

[Zed Head]

Can you find an S and an L over by the T plug?  The yellow wire and the white/black wire.  That would be the lock.  But the "P" terminal is a pretty good clue also.  I think that it only comes on the ZX alternators.

Just took a picture of an OReilly Ultima alternator I had on the shelf.  Looks just like yours.  It's a ZX unit.  I'll post a picture in a second.

[Zed Head]

Here it is.  I think I took the condenser off and used it to solve a different problem, so it's not there.  The P terminal is a tachometer signal that some ECU's use.  Only heard of it on internally regulated units.

[Zed Head]

Here's the thing though - they have to set their test machine up as either internal or external regulation, I think.  I'd take it back and make sure you get a guy who knows what he's doing and make sure he tells you if it's internal or external.  

If you have a part number from the box it came in we could do some detective work also.  Could be that the reman guys are packing different things in to the same cases.

[jlenownnab]

With a little luck I can get them to order me a external regulated alt, With a little luck. I am getting ready to get my z's dialed in, I will be on here more and more. I will post alt outcome. Thanks again

Stewart

[Zed Head]

Good luck.  By the way, I'm not really sure the P terminal is for.  But it didn't show up until the 280ZX.

[jlenownnab]

Just spoke with oreilys..... He said that the alt they have sold me is the only one their computer calls for. He also said that it is a 60 amp externally regulated counter clockwise unit. He said he is 100% sure it's the right alt?????

[Zed Head]

Dave WM's has the P terminal also, in his video, I see.  The reman companies have consolidated their parts lists down so that just a few will cover a lot of cars.  Looks like they're putting the P terminal everywhere now.  Sorry about the misdirection.  

If you post some part numbers....  Can't emphasize enough how untrained the typical parts store employee is.  All they know to do is key letters and numbers in to their computer and do what it tells them to do.  Occasionally somebody will actually know some car stuff, but the majority don't.  It's just the way things are.

In the meantime, the Factory Service Manual has all of the testing procedures for the stock system.  Your mechanic really needs to go there.  It's free!

http://www.classiczcars.com/files/file/22-1975-280z-factory-service-manual/

 

[Zed Head]

Should also note that people get bad alternators straight from the shelf.  That's why they have a lifetime warranty.  But if you're not getting power at the T plug, the alternator can't work.  That's probably where your mechanic is stuck.  Since the engine runs on the battery, focus on that.

[jlenownnab]

He has a lot to go off of in the morning, he is really good. thanks again, I will let you know out come.

stewart

[Dave WM]

One thing I don't recall seeing, exactly how do you know the alt is not charging the battery?

It should go without saying that you should have a good battery AND good cables with good grounds, and good clean contacts at the battery post.

simple test would be to disconnect the FN plug (field coil and "signal wire) from the alt, start car, check the voltage at the battery. the alt will not be producing any charging current since the field is disconnected. This is the baseline voltage with no charging. You will hear the difference when you plug the FN plug back in as the alt loads if its working.

Next plug in the FN plug check the voltage at the battery rev the engine up some see if the voltage changes. if it does then you need to find out why the charging meter is telling you its not (forgot to ask

If voltage at battery with the alt hook up does not change (go up) with the alt FN plug hooked up then the alt is not working, either do to a fault of the alt or the regulator or the wiring or the fuses.

to check the alt get a jumper (I used one with small alligator leads, insulated) hook from the F alt term (look at the alt to figure out which one is F from the photos above) to the BAT term. Oh and confirm there is 12v AT THE BAT term should be at all times, its directly hooked to the battery (thru a fuse link). Once you have the jumper in place start the car and see if the battery voltage is still at the base line. This is the FSM test Zed posted to bypass the regulator. DO NOT rev up the engine just a little above will show if the alt is working checking the voltage to see if it goes up.

One last thing, the fuse box is not precise about what the fuse protects, so don't assume its only what it says. if you find a blown fuse replace it as the FIRST thing to do when trouble shooting. Also after replacing it and try testing check it again. Very possible its blown again in which case you must figure out why its blowing. I have found broken but not blown fuses I guess do to age/vibration etc... if the replacement fuse blows right away then you must figure out why before going any further. Make sure if you replace a fuse its the correct amp rating.

 

Edited July 2, 2016 by Dave WM