Debugging my battery charger

[ard]

I noticed that my old Schuhmacher battery charger which connects to the cigarette lighter wasn't charging my P-car's battery. I connected a modern Deltran unit directly to the battery terminals and it fully charged the battery so I know it's not the battery that's the problem.

Naive question but when I plug the Schuhmacher into a 110V outlet I should be reading 12VDC across the tip of the cigarette lighter plug and the spring-loaded metal "clip" on the perimeter of the plug indicated with red arrows in the attached picture, correct? Right now I am getting 0V, which leads me to suspect that the plug has a problem.

Thanks in advance.

[oldE]

With that unit, does the tip piece have to be depressed to complete the circuit?
If not, you might have a broken contact within the plug.

Best
Les

[dad911]

I'm not sure about that one but the smart schumacher chargers will not read voltage with a volt meter without a battery connected.

Are the lights working on the charger?
If you measure across the car lighter jack, does the car measure 12v?

[pwd72s]

Or the charger itself...not familiar with that brand of charger, but it should be producing more than 12V...if memory serves, mine puts out 13.4v. I have a set of multimeter leads that probe a pin into the wires themselves. Best way I can describe them is that they have a hook shape tip to hold the wire, with a needle like spring fed probe to penetrate the insulation. Look for test lead sets on Amazon.

Anyway, I'd suggest bypassing the plug, and testing the wires. If you still get zero...yep, time for a new battery maintainer.

[Turbo_pro]

via GIPHY

[ard]

Thanks for the quick responses. See below:

Originally Posted by oldE

With that unit, does the tip piece have to be depressed to complete the circuit?
If not, you might have a broken contact within the plug.

Best
Les

Thanks, I tried while depressing the tip and still observed no voltage

Originally Posted by dad911

I'm not sure about that one but the smart schumacher chargers will not read voltage with a volt meter without a battery connected.

Are the lights working on the charger?
If you measure across the car lighter jack, does the car measure 12v?

The green light indicating that the charger has power comes on. The red light which indicates that the battery is fully charged used to come on but no longer does. I thought the probes of the multimeter would complete the circuit and I should be able to observe a voltage potential without a battery connected. This unit is vintage 1995 and therefore likely not a smart charger.

Originally Posted by pwd72s

Or the charger itself...not familiar with that brand of charger, but it should be producing more than 12V...if memory serves, mine puts out 13.4v. I have a set of multimeter leads that probe a pin into the wires themselves. Best way I can describe them is that they have a hook shape tip to hold the wire, with a needle like spring fed probe to penetrate the insulation. Look for test lead sets on Amazon.

Anyway, I'd suggest bypassing the plug, and testing the wires. If you still get zero...yep, time for a new battery maintainer.

I will try probing the wires directly. Thanks

[dad911]

1995? I'd replace it with an automatic smart charger and not look back. Probably better for the battery also.

[cstreit]

Most of those cigarette lighter plugs have a fuse inside. I'd check that first.

[pwd72s]

^Good thought! Also, is the fuse controlling the car's plug in still good? Remember once thinking a radar detector had died..turns out I'd somehow shorted the cigarette lighter outlet and had blown it's fuse.