Electrical Problem

T

Tim E

New member
Hi…looking for thoughts on an electrical problem. I have a ‘29 Standard Coupe that has developed an electrical problem, an intermittant 20 amp short that drains the battery.

The car is somewhat new to me, so I am yet to be fluent in Model A’ese but here is a description of my problem. Had been driving the car daily for a week or so and everything was fine. Parked it overnight and woke to find the 6-volt battery dead. As it wouldn’t take a full chance and was over 5-years old I replaced it. That seemed to do the trick and I was good for a couple days. Then it happened again!

Was driving, came home, turned off the key and the amp meter dropped to minus 20 volts. To prevent the battery from draining, I popped the aftermarket main fuse on the car and then searched for any obvious shorts…didn’t find anything. Seems unusual to me to have a high voltage draw when the key and engine are off, but not when the car is running. Thinking that next I’ll unscrew the dash instrument panel and check for an short in the ignition switch. Might anyone have have any other thoughts?

Thanks…Tim
 
Tim. I have no solution only sympathy I have a 30 Coupe that I have owned for 45 years with the same issue. I have chased wiring from the battery to every connection, to no avail. My solution was to place a dead out switch from the battery to the starter.. i'll be watching if someone out there has an answer. Rick
 
If it has the original generator, the cut-out relay on the generator might be stuck closed. Check for that. If that is the case, the battery would discharge through the generator when not running.
 
Tim E said:
Hi…looking for thoughts on an electrical problem. I have a ‘29 Standard Coupe that has developed an electrical problem, an intermittant 20 amp short that drains the battery.

The car is somewhat new to me, so I am yet to be fluent in Model A’ese but here is a description of my problem. Had been driving the car daily for a week or so and everything was fine. Parked it overnight and woke to find the 6-volt battery dead. As it wouldn’t take a full chance and was over 5-years old I replaced it. That seemed to do the trick and I was good for a couple days. Then it happened again!

Was driving, came home, turned off the key and the amp meter dropped to minus 20 volts. To prevent the battery from draining, I popped the aftermarket main fuse on the car and then searched for any obvious shorts…didn’t find anything. Seems unusual to me to have a high voltage draw when the key and engine are off, but not when the car is running. Thinking that next I’ll unscrew the dash instrument panel and check for an short in the ignition switch. Might anyone have have any other thoughts?

Thanks…Tim
Click to expand...

Cutout sticking, Disconnect the wire to the cut out and put the fuse back in to check.
Bill
 
Thanks for the thought…worth checking. Question, if the generator cutout relay was stuck, would the generator run until it depleted the battery? I did not hear anything running along with the 20 amp draw.

My interim no battery power solution was to remove the aftermarket main fuse, jump the battery and drive the car home. I watched the amp meter all the way and it was showing between 3 and 10 amps positive…all seemed fine. However, after I parked the car in the driveway and turned off the key, rhe 20 amp negative draw showed up again. I didn’t hear the generator running and no lights were on…again. i removed the main fuse. It’s a mystery but there is a solution…

Tim


Tim
 
That does sound like a defective cutout. Either the points are sticking closed or if a diode type, it is shorted.

If you'd like to send me your cutout, I can test, repair or replace it with a refurbished and tested original Ford cutout. Here is a video I made that explains how a cutout works and all the things I do when refurbishing them. PM me if interested.

https://youtu.be/rnuukBeJ6Zs
 

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When the cutout's points stick closed and the engine is off, the battery sees the generator as a load and tries to make it a motor. However, the generator will not turn because of the fan belt. The result is a massive battery discharge. The battery needs to be disconnected immediately to prevent smoke, burning wires and damage to the generator. Replace the cutout with a solid state one rated at 20 Amps or more. Better yet, eliminate the cutout by converting to an alternator.
 
Tim, I'm assuming this is an "overnight" battery drain. Try this, put your key in the ignition and wiggle it (don't turn it on) while watching the ammeter. If there is a lot of movement in the needle, then it's probably the ignition switch. Good luck!
Terry
 
A bad brake light switch is common on model A but it won't draw 20-amps and generally the brake lights will be on and noticeable. The ignition coil won't draw any more than 4-amps as a general rule but either of these will draw the battery down within hours.

A 20-amp draw is likely a generator situation since a dead short would blow a fuse pretty quick if so equipped. The generator may hum if power is getting back flow through a stuck cut out switch or a bad power diode but it generally won't turn due to belt friction. It is designed to be a generator and even though shunt wound the design makes for a poor motor. The starter is also shunt wound but it's design is made for high torque and uses four heavy wire field coils and four brushes to get the armature to turn. It also draws a lot more current when operated.
 
Thanks to all who have offered their guidance on my periodic severe electrical drain. Today I am going to replace the generator cutout relay. As electrical drain is severe, depletes a
fully charged battery in minutes, the generator’s cutoff relay seems to be a likely suspect. I’ll update you as I learn more.

Tim
 
So Far, So Good…

This morning I swapped out my replica generator cutoff relay for a rebuilt vintage Ford one. I have been road testing the repair this afternoon and I am happy to report that my severe electrical draw has yet to reappear. To all who assisted in diagnosing the problem, thank you.

A note; the problem was only occurring after I drove some distance and then turned off the key. At that time the amp meter would show a draw of around 20-volts. Towards diagnosis, I drove the car for 30 minutes, turned off the key and watched the amp meter drop immediately. A friend tapped the relay housing firmly with a screwdriver handle and like magic, the draw stopped! That pretty much confirmed that the replica relay was the problem. As of now, my ‘29 Standard Coupe is on the road again…

Tim
 
The repro cutouts are a known problem. Seems some are better than others but definitely a quality issue. I use a Fun Projects voltage regulator in place of the cutout, although I'm not sure if they are available now.
 
I purchased my first A in 1963 or 64. l was in High School. Several of us had A’s and little money. We all kept the cover off the cut out switch and kept a wooden stick on the dash rail. Every time we shut down, we checked the amp meter. If it went negative, we hopped out, opened the hood and pried the little set of points open. Ernie in Arizona
 
A properly serviced cutout is very reliable and trouble free. The problem is most people just throw one on without giving any thought to serving it. See the video link in post #7 above. I explain how to set the point gap, point alignment, air gap, dress the points and closure voltage.

You wouldn't run a 90+ year old generator without servicing it. The same goes for the cutout.
 

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All one needs to do if stuck cutout points are suspected (such as when the ammeter reads discharge after shutting off the engine or the battery mysteriously drains itself) is to lightly tap the top of the cutout cover a couple times with a wrench or small hammer. You might hear a metallic "Ting!" as the spring pulls the points apart. No need to remove the cutout cover unless you want to inspect the internal guts or clean the point faces. This is only a temporary "fix" to avoid a drained battery and possibly an electrical fire. The cause of the stuck points should, of course, be investigated and repairs/replacement made.
This problem is by no means a new phenomenon in Model A's! Anyone who has been in this hobby for a long time has probably experienced stuck cutout points, followed in short order by a dead battery. It happened to me at the 1974 MAFCA Queen Mary Convention in San Diego! How embarrassing after driving all night from Phoenix to attend the event! Dead in the parking lot the next morning. :( For a while during the 1970's and 1980's, some really poor off-shore cutouts were flooding the country, abetted by an unscrupulous national Model A vendor selling known defective and "seconds" parts of questionable quality for less money than what reputable dealers could sell quality parts for. And many parsimonious Model A owners bought the cheaper cutout - with predictable results. Old-time Model A dogs on this website don't need to be told who that vendor was! If a Model A owner continually experiences a "stuck cutout" as we call it, I'll bet it's one of those 1970's-1980's off-shore jobs!. There are still a lot of those good-for-nothing off-shore cutouts floating around these days, especially in restoration projects from that period or in cardboard boxes full of parts at swap meets. Caveat emptor!
Marshall
 
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