battery drain

[Zed Head]

On 8/18/2021 at 5:52 PM, Dolfinz said:

When the battery has a full charge the car starts just fine but the alternator gauge has a slight negative reading. 

The only draw on the battery would be the clock.  And that is so small that it won't drain a battery for months.

Still not really clear what problem you're trying to solve.  You showed that the alternator is discharging while the engine is running, which means the alternator is not working.  That will drain a battery pretty fast, with spark and fuel pump and various relays drawing power.

A super simple check for a key-off draw is to watch and listen for a spark when you connect the last battery cable.  I had a single relay active after a wiring change (alternator modification) and it created a significant spark, it was a clue that I had a problem (along with the battery dying overnight).  I think it was drawing 0.3 amps.  Once I fixed the draw even the clock didn't produce a significant spark even though it worked just fine.

[S30Driver]

To verify the new alternator is not charging the battery,  measure the voltage across the battery with the ignition off, then measure the alternator output terminal with the car running, maybe 1000 rpm.   If they measure the same, the alternator is not providing a charge and the problem is likely a bad rebuilt / new alternator or as SteveJ has mentioned, the external regulator.  If the alternator is working, you should see somewhere near 14v on the second measurement.

[Dolfinz]

The engine is drawing on the battery not the alternator.  There is no draw when the key is off only when it is running.  This  is a second alternator and the engine has done the same thing with both.  The first one was only a couple years old and I had it tested and it was good but got a new one because the plastic cover on the back got lost.  I had the same problem with it before I replaced it so the alternator doesn't seem to be the problem.  Like I said previously, I'm going to pull all the fuses and see if that helps.  But now I'm thinking the engine won't run then because the electric fuel pump won't get power.  I'll try the measurements above but expect that if something is draining the alternator it's still going to look like a bad alternator.  I'll try it with white/red wire disconnected from alternator output.  As for the current draw, what would be the normal current draw to charge the battery while the engine is running and everything else is off?

[Zed Head]

Sounds like your L wire is not providing power to the windings.  Check for voltage at the L wire with the key on.  A good alternator with no L power will not charge.

Actually with an external alternator, it's the F terminal.  No F power, No F'ing charging.  Check inside the plug with the key on.  sometimes the connection canget loose too, so if you find power make usre it's a solid connection to the F terminal.

Check your grounds also.  The alternator case should have a ground through the monuts but it also has a dedicated ground wire.  No ground no charge.

[Dolfinz]

Thanks for the advice.  I will check it.  I know it has a good ground as the black ground wire is connected.  It is possible that the F wire isn't a good con nection as the molded plug broke due to age and only the spade lugs are left.

[SteveJ]

So did you do any of the things I suggested in Post #6?

[Dolfinz]

Been too hot and humid here in Phoenix to work on the car.  I'm hoping to get some time this weekend.

[Dolfinz]

Zed, It finally cooled down enough for me to work on the car.  So, as you suspected there's no +12 at the F terminal to the alternator, white/black wire.  I traced the wiring via the vehicle schematic and this wire goes through the voltage regulator and the electric fuel pump relays.  Any reason I can't just run a new wire from the ignition switch ON wire to the alternator?  It would save a lot of troubleshooting of the wiring in between if I can.  Let me know.

[SteveJ]

Yes, you are bypassing the voltage regulator. This could cause you other voltage/current problems.

Replace the voltage regulator. https://www.thezstore.com/page/TZS/PROD/classic10b03/12-4082

 

[Zed Head]

I would check for power at the regulator plug from the main harness, and test for continuity from the regulator down to F.  The circuit could be broken before, inside, or after the regulator.

Looks like the switch powers the F wire and the L wire separately, in a parallel circuit.  I never really looked at the circuits in detail, for the internally regulated system they just use one L wire straight to the alternator.

I tried to post the FSM drawing but it failed.  It's on page EE-13.

 

Edited October 1, 2021 by Zed Head

[Dolfinz]

I know it's been a while but I had to wait on a new voltage regulator; which I received and installed, and I've been working on getting turn signals, headlights, horn etc. operational.  This required having all my steering column switches rebuilt.  These are all completed and I'm back to addressing the alternator issue.  I have verified continuity of the F wire from the regulator to the alternator( this is a white/blk wire). What I haven't been able to determine is the color of the wire at the regulator plug that is supposed to go hot when the ignition is in the on position.  The white wire is constant +12,  the black wire wire is ground and the yellow wire goes to the alternator N terminal.  Can you advise as to the color of the wire from the harness that is supposed to be the IG connection?  The blk/ylw goes hot with the ignition switch on but if that's it why doesn't the wht/blk F wire get voltage?

I'd appreciate some further assistance.

[SteveJ]

So when the key is on, the B/W wire has 12VDC. The Y wire will have about 7 to 8 volts with the alternator turning (full alternator voltage divided by the square root of 3).

The B/Y wire is just to provide a ground to the hell-hole known as the Ignition Interlock Unit (Boo! Hiss!) Chances are that it has already been bypassed in your car. Note that in other parts of your wiring, B/Y is 12VDC when the key is in start and goes to the Interlock Relay (Again, Boo! Hiss!).

B is your ground. W is your battery voltage and goes to the alternator through the WB wire when the appropriate contacts are closed.

 

 

Edited November 1, 2021 by SteveJ