1950s Parasitic draw - any ideas?

[Laspaz]

1954 Series 75 Cadillac. Battery holds charge when disconnected, otherwise drops overnight.

Definite sparks when connecting the battery cable. About 2.2 amp parasitic draw. 3 wire alternator, no significant change with the two wires to the alternator disconnected.

Here is a video showing voltage and current draw:

https://www.youtube.com/watch?v=eFomiwtbk4o

Happy to take suggestions on what might be causing such a draw. Thanks.

[Wbostoen]

There is a perfect tool for these kind of problems: a thermal camera. I got myself one last year and wish I got it sooner. I chose a standalone unit but you can buy these as add-on accessoires for your smartphone. Saved me loads of headache. These things pick up a fraction of a degree difference, you can see the path of current in the blink of an eye.

[V63]

I would first suspect the alternator.

[TJ Hopland]

Next step would be to pull fuses to see if what ever it is is fused.  If it is a fuse at least that should narrow down what you are searching for. 

[tluke]

Check this post: 1958 battery drain 

It suggests several approaches:
1) Remove fuses one by one and measure the amperage (as your video shows). If removing a fuse reduces or eliminates the draw then you know the circuit to check. You can also disconnect each fuse separately and put your multimeter leads to each connector in that fuse case and see if there is a draw. If the problem is found to be a circuit with bulbs on it you can remove each bulb until the draw disappears. Glove box and trunk lights not being turned off by the latch closing have often been the culprit with parasitic leaks since you can't see them when their supposed to be off. Both are on the always-live body feed circuit (see below). If the fused circuit has no lights you'll just have to chase down the wiring for a short to ground for that circuit. Most fused circuits in '54 have no power unless the ignition is turned on so it is unlikely to be causing the parasitic draw. Most shorts cause heat (blow the fuse) and eventually fires (if no fuse) so bulb or relays staying on is most likely to be the cause.
2) On the '54 75 series the body feed circuit (courtesy/dome lights, rear reading lights, clocks, lighters) doesn't have a fuse but comes directly off the headlight switch's always-live circuit (orange wires) and uses the headlight switch thermal breaker as the circuit fuse. The clocks are mechanical and only use power when they wind so as far as I know they would only have an intermittent drain. I guess the winding could malfunction and always draw power, never appearing to be "fully wound". The wiring under the door sills is a good place to start looking for shorts especially on the drivers door since it branches off from the rear dome light feed to the rear clock and the rear reading lights. However, since shorts normally heat up and blow fuses it would trip the thermal breaker in the HL switch. After several seconds it cools and reconnects then trips again, etc. etc. etc. Again, bulbs or relays more likely to be the culprit.
3) Some say a stuck window switch may cause a parasitic draw. I'm not sure since the power window switches have a built in circuit breaker and don't use relays. One post mentions this as actually happening.
4) The power windows, power seat and divider window all have a circuit breaker that is located behind the driver's side kick panel (where the heater vent is).  Since in '54 the windows/seats are powered with the ignition on or off you can check this the same way you would a fuse except at that circuit breaker. Put a test lead on each side of the breaker and see if current if flowing when no window or seat is being moved.
5) A few have suggested the voltage regulator my be the culprit but your post mentions an alternator which eliminates the need for a VR. If you indeed have a generator then disconnecting the battery wire on the VR can check for an issue with that.
6) I had an issue with a short in the steering column but that resulted in the horns honking whenever the batter was connected so I disconnected the horns under the hood. The column short is a short on the ground wire, not the power wire. The horn relay still clicked each time I connected the battery and I measured a small current flowing ( I can't remember how many amps but enough to keep the magnets energized in the relay). For me disconnecting the horn relay (next to the VR) brought the drain down to zero until the short could be eliminated.

Good luck

[Laspaz]

Amazing reply thanks tluke, will work through this tomorrow. Cheers!

[TonyZappone #2624]

Years ago, I had exactly the same problem with one of my '56 Derham series 75 cars.  One evening, I sat in the rear seat smoking (yes, checkout my bypass scars) it was quiet and dark.  I heard a click, and a pause, and another click.  One of the window switches in the rear left console was shorted.  There are so many switches on these series 75s, check them out

[bcroe]

I have placed a 12V bulb in series where you connected
the meter, sized to light on your drain.  Place the bulb
where it can be seen (up by windshield here).  Then go
disconnecting things, all the while watching for the
bulb to go out.  good luck, Bruce Roe

[Chopper1942]

There is an issue with pulling fuses. Sometimes if a fuse is pulled, the draw stops and when the fuse is reinstalled, the draw is not there.  There are two other methods to determine which circuit is the issue.
 
1. Use your DMM on the mV scale and check the voltage drop across each fuse. The higher the fuse rating, the lower the mV drop across the fuse. for example, a 10 amp fuse would have almost 20 mV drop, a 20 amp fuse a 10 mV drop, and a 30 amp fuse a 7mV drop, for a 2.2 amp draw.

2. Use a thermal imager. The fuse with current flowing through it will glow red/orange. You can use the imager to check components in the circuit to see which one is drawing the current. For instance, if the generator/alternator is shorted and drawing current, one of the wires going to the generator will glow. The thermal imager is the quickest and easiest way to diag which circuit is drawing current.

The first item I would check is the generator. disconect its wires and see if the draw goes away.

[Lexi]

Yes, Bruce is correct. In the old days the mechanic would disconnect your negative battery terminal, then attach a 12 volt test light between the battery terminal and the disconnected cable. Make sure everything that normally draws power is off, including having the doors shut, (i.e. no courstesy lights on). Probably best to disconnect the clocks. Believe your Limo has one in the center of the bulkhead that separates the front cabin from the rear salon. See Terry Luke's post, item #2. If the tester lights up then you have a draw somewhere. As Bruce suggested start disconnecting things to see what turns off the test light. That should isolate the problem. Best to work with a helper. A test light is an inexpensive tool and worth the investment. Just stick the sharp end of the probe into the negative battery post and attach the alligator clip to the loose cable. See attached image for a shot of a 6 - 12 volt tester in one of my electrical tool kits. The tester is the red colored device in the top of the photo. Clay/Lexi

[Laspaz]

Thanks so much for all the ideas, I went around trying all the lighting switches (my interior lighting does not work properly), the door switches, the dash switches, made sure the radio was off for the third time.

Was sitting in the back thinking what the hell and was trying the window switch in the rear side console, and the button there too, tried pulling out the cigarette lighter to make sure it wasn't stuck on and realized it wasn't a cigarette lighter but a knob for the rear radio controls. Rotated the knob and bingo. 🙄

Thanks again for the help, good to get this fixed. 👍

[Lexi]

So you have the rear seat radio control package. Nice. Yes, the cigarette lighter looking knob is the on/off and volume switch, switch for the radio. I have the rear radio controls also in my car. Think in my Limo this only works when the key is on though. Now you got me wondering. Next opportunity I will check mine to see if it can also draw if left on. If you still have a problem, I can think of a couple of other items to check jus in case: 1) Trunk light, and 2) Curb lights, which I think your car has. One underside of each of the rear doors. Keep us posted if need be. Clay/Lexi

[TJ Hopland]

I was about to ask what the heck a rear seat radio control package was.   My brain went to like a model airplane and there was some sort of wireless control unit that could control the movement of the rear seat.  I was thinking of a rich guy that wanted to adjust his seat before he got into the car.  Rear controls for the radio don't sound as exciting.     

[Lexi]

LOL. They actually are exciting. In my Series 75 I can put up the divider window, turn on the radio, cut out the Chauffeur's front speaker and with the red button that lights up, signal seek by depressing it and choose my own station. The Limo radio is a different model than the others at least for my year of car. It is not wireless as there is a heavy cable that communicates with the rear controls on the RH passenger side. That is why there is no option, no port, to install a foot control in a Limo, (at least in 1956), on the radio itself. That is because the additional signal seeking option is now in the rear seat. That said, the front radio controls still have the wonder bar which is fully functional, unless of course those in the rear salon decide to overide it. So externally, the 1956 Radio looks the same, but has some different features. Clay/Lexi

[Laspaz]

LOL. They actually are exciting. In my Series 75 I can put up the divider window, turn on the radio, cut out the Chauffeur's front speaker and with the red button that lights up, signal seek by depressing it and choose my own station. The Limo radio is a different model than the others at least for my year of car. It is not wireless as there is a heavy cable that communicates with the rear controls on the RH passenger side. That is why there is no option, no port, to install a foot control in a Limo, (at least in 1956), on the radio itself. That is because the additional signal seeking option is now in the rear seat. That said, the front radio controls still have the wonder bar which is fully functional, unless of course those in the rear salon decide to overide it. So externally, the 1956 Radio looks the same, but has some different features. Clay/Lexi

That's interesting, I think the rear controls are pretty neat too. I do have a second foot switch for the driver which I assume is for the radio though... Hmm.

[tluke]

I almost mentioned checking the rear radio controls in my initial reply but it was already way too long and like Clay I assumed it only received power when the key was turned on. It is kind of a magical setup as he stated. Pressing that little red button on the rear armrest console and voila! -the station just changes.

I do have a second foot switch for the driver which I assume is for the radio though... Hmm

Depending where it is located, that second foot switch may be for the autronic eye and the headlights. If its above the regular high beam foot switch it is the override switch for the autronic eye.