1.5 Volts Across the Points

stewwolfe

stewwolfe

Senior Member
I'm stumped. My Model A started but then quit and wouldn't start again. When I checked the ignition (always the first thing I check) I found 6.23 volts everywhere except across the points, where I have 1.5 volts (and at the positive side of the coil). I've replaced the points, condensor, and the coil. I've also stripped down the distributor to make sure I didn't have any corrosion giving me a poor connection. Does anybody have any other ideas about what could cause this situation? Thanks in advance.
 
Hi Stew, the coil should have 6 volts to ground on one side post even if the ignition switch is off. If you do not have the 6 volts, check the in-line fuse if you have one. Sometimes they corrode. Next, jumper the ammeter out by placing a jumper between the terminal block screws and see what you have. Call me if it is still not running tomorrow, Saturday, morning.
 
Hi John,

The coil is hot and give a 6.24 volt reading when he switch is off on both sides. When I turn the switch on I get a little over 5 volts on the negative side and 1.5 on the points and positive side. I'll jumper over the ammeter in the morning and see if that corrects the issue. I didn't think about the ammeter because it is showing a discharge (slight which is normal for my car) when the ignition is turned on. If it. Doesn't work, I'll call you in the morning.

Stew
 
I've had similar problems before. Partial short. One time in a bad pop out cable. Another time in the lower distributer plate. Have fun and good luck chasing it down.
mike
 
I'm sorry if this sounds stupid but did you place a piece of paper between the points to open them when you took the readings?

With the points closed you will have 6 volts on one side of the coil and 0 on the other. If you have a low voltage at the arm with the points closed you have dirty. maybe burned, points. If this is the case after cleaning the points check for a strong blue spark. If not replace the condenser.

With the points open and the key on you should get 6volts both sides of the coil and the points arm to ground.

If not remove the condenser and check again if it comes back, replace the condenser with one of the burnout proof units sold by the vendors do not use one from a modern automotive parts house.

If still no joy remove the upper and lower plate of the distributor and check the wire as it enters the distributor for 6 volts with ing on. If not then I would suspect the ign switch.

Please keep us informed!
 
First I'd use an analog meter rather than a digital meter, but with the engine not running you'll do OK with your digital meter.

With the points open and the key ON you should have battery voltage all the way to the movable points contact. As soon as the points close both points contact should show 0 volts because they are both grounded. If they show some voltage such as the 1.5 volts you mentioned, then the contacts aren't making good contact with each other, or the cast distributor body isn't making a good ground to the head. You can test this by using a good jumper wire, say from the condenser ground screw to a head nut.

Measure the voltage from a good ground, such as a head nut, to the non-movable points contact, then move the lead over to the movable points contact. Both readings should be 0 volts, but if the movable contact shows any voltage more than the ground contact, then you know the points contacts need to be cleaned.

From the coil + to ground with the key ON and points closed you should show 0 volts, but due to a small resistence in the wire between the points and coil, you will show some very small voltage reading at the coil +, but it should be under 1 volt.
 
A couple years ago we had a very wet and humid spring, so my A stayed parked in the shed for several weeks. When I tried to start it I had no spark. The spark was perfect when I opened and closed the points with my fingers, so I cleaned them with some fine sandpaper, then ran a piece of thic cardboard through them. Still no improvement, so I got out the hand crank and it fired right up on the first pull. Once it started with the hand crank it was fine the rest of the summer. Just one of those mystery times when the points must have still had a touch of oxidation until the engine ran.:confused:

Give your hand crank a try, but be sure to turn the key on before you wear yourself out.:D
 
I had to add a ground pigtail to the plate to insure a good ground for the points. This post just turned me into a senior member!
 
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I've reached an age that I'm not willing to say they are all bad.

The good news is that I've gotten it running. John came over this morning and ended up being as baffled as I was (and John is one of the experts in our club). I had bypassed the ammeter by jumping across the terminal box, but decided that I would pop the dash off and jump the ammeter there (since we had gotten to the point of grasping at any straw we could). When I pulled the dash I noticed that the modern style ignition switch had a loose connection that had rotated back, hit the tank, and through a period of vibrations and bumps, had rubbed through the paint. When you hit the right bump, or vibrated enough it would short out on the tank, and voila, no spark. I tightened the connection and wrapped the whole thing in electrical tape, so that if it vibrated loose again it can't move and hit the tank, and it suddenly had 6.23 volts across the points, and when cranked, fired right up.

These 82 year old cars sometimes send us on a wild goose chase.

Thanks for the input, and assistance, the people on Ford Barn are great!
 
stewwolfe said:
You're right but I haven't figured out how to fix my pop out yet.
Click to expand...

Search the forum as it has been talked about here before or just start a new thread if you have trouble finding what you need in the search as it will make for a better search result in the future.
 
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stewwolfe said:
You're right but I haven't figured out how to fix my pop out yet.
Click to expand...

Does your popout have the removable rear steel cover? This would be the popout for the round speedometer, and I've posted pictures and how I restored one. Try the search feature and see if you can find it, and I'll also try to find it. I don't always have luck in searching.:mad:
 
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