Die Hard battery charger output voltage only 9V

Thread Starter


Joined Sep 20, 2009
Hi all. First of all I am a newbie and not well versed in electronics so please bear with me. I was using my Die Hard automatic 12v automotive charger yesterday and heard it go "click". I disconnected it and measured the output voltage and it only read 9 volts. Now I thought the voltage should be around 13 so something appears to be broken. Is this something that can be repaired ? Thanks in advance.


Joined Apr 5, 2008

Do you have the schematic of the charger?
Can you post some photos of the innerworks of the charger?



Joined Jul 23, 2009
Hi JL66RedCp,

This kind of post really shouldn't be tolerated here. You ask the help of us experts with 10, 20, 30, and more years of experience, yet you give almost no information about your problem. Do you think we're mind readers? Well, we're not. With such scant information, none of us can help you right now.

First, there may or may not be a problem with your charger just because it made a noise. Depending on the sophistication of the charger, it may not put out 13-14 VDC without it being connected to a load (battery or resistive load). Second, you absolutely need to check the simple things first. Like, are any of the fuses blown? If not, the noise may be pointing to a contactor or relay, witch is relatively easy to check using a DMM. After that, it's essential that you visually look very closely for any damaged components, like burned resistors, or plastic transistors with pieces of the plastic blown-off, or electrolytic caps that have had the safety pressure release popped and had electrolyte released. If you have eliminated all of those, then a simplified schematic as best you can would help us the most. If you have a factory schematic, that's far better. And several close-up photo's of the units' circuit board(s) and transformer, and controls. Especially check the on/off switch, and the power transformer (with the unit unplugged and off for at least 10 minutes). All windings should have continuity and the on/off switch should be easy to test with an ohmmeter or a continuity checker. The transformer may be a bit harder to determine which wires go together on a winding. Often, there are very small fusable links made of a strand of AWG#: 40 wire or similar, designed to open on a short circuit and this may have happened.

Check all this stuff as best you can, take photos as I sugessted, then reply to this post and we'll go from there. But please understand that we can't just wave our magic wands over the post and say ah ha, I've got the fix. We need info about it.

Good luck,
Kamran Kazem,


Joined Aug 7, 2008
Without a battery for a load, you may see some strange readings. If you connect a capacitor acrost the output , you might have a V reading abnormally high. Try using a slightly discharged battery,and measure every few hours. The click could be from a thermal circuit breaker resetting.

Thread Starter


Joined Sep 20, 2009
Sorry Folks -- soon after I created the post I got very sick and was pretty much couch/bed ridden. I belong to several Corvette restoration forums and several Small Gas Engine/Power Equipment forums. I never let this kind of thing happen.

Yes, I do have the wiring diagram and parts list for the charger. They are contained in the manual which I also have. It is a 10/2 amp 6/12 volt charger with a 50 amp 12 volt engine start. It is a sears model 608-50310.

I do not knwo how to post a picture to this forum. I can scan the wiring diagram and parts list and maybe send it to someone who can post it for me.

Thanks in advance and again -- I apologize for what has transpired.