Charging System Diagnosis

A

alvisoroadsters

Member
Hi All,
Stock '28, 6V positive earth. Car ran like a champ one day, the next day....no crank. Noticed the lights wouldn't illuminate, so I charged the battery all day (to no avail). Pulled the battery out and the case had swelled up quite a bit!

Put a new battery in, looked at the ammeter and it was pegged negative (Key off). I disconnected the wires to the cut out and the ammeter returned to 0 (Key off).

So...I think my cutoff is stuck closed, and the generator drained the battery overnight. I've pulled the fuse on the starter - I noticed the ammeter goes to 0 when this happens. If you all could help me, I've never diagnosed a cut out before...


1) When you pull the wires off the cutout, the load on the gauge goes back to zero. The battery was drained FLAT overnight after driving for several hours. Sound like a cut out stuck closed?

2) For the time being, will removing the fuse when the car is parked should prevent the stuck cutout from drawing all the juice outta my battery?

3) Thank you all in advance for any support - I have looked in to the diode/voltage regulator type cut outs and think those might be a slick way to go. I'll see if the local old Ford store has one in stock...

Thanks!!
 
Lets look at the wiring diagram and see what's happening;

wiring-diagramcolor2sm.jpg


The solid yellow wire is where the fuse would be in the diagram.

So the removing of the fuse removes the power to everything when the motor is not running.

Remove the wires from the cutout and put the fuse back in and see what happens. You can also remove the belt from the generator and see if it runs like a motor with the fuse in.
 
Hi Mike,
Thank you for the diagram. This will come in handy...

With the fuse in and the wire off the cutout, the ammeter reads 0 amps. Putting the wire back on the cutoff with the fuse installed makes the ammeter read negative 20 (or so, it buries the needle in the left side of the gauge).
 
alvisoroadsters said:
Hi Mike,
Thank you for the diagram. This will come in handy...

With the fuse in and the wire off the cutout, the ammeter reads 0 amps. Putting the wire back on the cutoff with the fuse installed makes the ammeter read negative 20 (or so, it buries the needle in the left side of the gauge).
Click to expand...

That's right, when you get a chance remove the wires from the cut out and report back what you see (I feel this will confirm the cutout sticking) you can also try hitting the cutout with a stick and see what happens. :D
 
I noticed earlier I was sparking a whole bunch trying to pull the wires off the cutout. I pulled the fuse, then removed the wires to test the amp readings. What would I see if the cutout is indeed faulty?

I'm liking this stick idea a whole bunch :D I might give 'er a whirl....
 
alvisoroadsters said:
I noticed earlier I was sparking a whole bunch trying to pull the wires off the cutout. I pulled the fuse, then removed the wires to test the amp readings. What would I see if the cutout is indeed faulty? With the fuse in and the wires disconnected, 0 on the ammeter

I'm liking this stick idea a whole bunch :D I might give 'er a whirl....
Click to expand...


...
 
put a testlight in line of a removed battery cable. a disconnect things one wire at a time until the light goes out showing no draw. it does sound like you may have a stuck cut out,
as per the diagram the yellow/ black wire at the cut out is the battery feed
 
Many of the repro cutouts are poor quality, so your best bet is to buy a restored original cutout or a quality diode cutout, such as the one made by A&L.

Bert's sells restored original cutouts. 800-321-1931
 
Pull the cover off the cutout and pry the points open. Had a Model A years ago and left the cover off the cutout as I had to open the cutout points every time the engine was shut off.
 
katy said:
Pull the cover off the cutout and pry the points open. Had a Model A years ago and left the cover off the cutout as I had to open the cutout points every time the engine was shut off.
Click to expand...

It would have been easier to install a switch on the steering column and run two wires to the input and output terminals of the cutout, and cut the wires from the cutout guts. Then you'd have to be sure the switch was turned on whenever the engine was running, and turned off as soon as the engine was stopped.

Or just use a good cutout.:D
 
Mitch How do you hook the test light up ? Is one end on the battery cable and other end on grnd? Or battery cable and starter switch? Thanks in advance RAY
 
Ray64 said:
Mitch How do you hook the test light up ? Is one end on the battery cable and other end on grnd? Or battery cable and starter switch? Thanks in advance RAY
Click to expand...

Hi Ray,
open up any battery connection then place the testlight in line...
i usually remove one of the batt ends, or u can use the batt to starter..
pos or neg doesnt matter..
give it a try then turn on any load ie:: headlights, etc and the test light wiil show the draw
 

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You don't say what kind of Ignition you have but if it's the "Pop out" style, check for internal shorts. These are notorious for draining your battery over night.When you shut the engine off, look at the ammeter, It should be at zero. If it shows a discharge, wiggle the key, If it comes back to zero, you have a bad ign. switch. I repaired mine by shoving a splinter into it till I can replace it.
Terry
 
Terry said:
You don't say what kind of Ignition you have but if it's the "Pop out" style, check for internal shorts. These are notorious for draining your battery over night.When you shut the engine off, look at the ammeter, It should be at zero. If it shows a discharge, wiggle the key, If it comes back to zero, you have a bad ign. switch. I repaired mine by shoving a splinter into it till I can replace it.
Terry
Click to expand...

I'll give it a go - thanks for the tip!
 
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