Diagnosing Battery Drain

[Humveeholic]

Gents, hoping you guys can help a brother out.

Recently acquired a 94 Humvee and have been in the process of replacing parts and getting it in good working order. Just prior to my purchase the owner bought two new 800CCA batteries which have had no problems starting up the vehicle. After about a week and a half of sitting outside I went to start it up and got nothing. No indication of power at all. Pulled the batteries, had them recharged then tested and they are good. After getting them reinstalled I decided to test for a draw by connecting my volt meter between the negative batter post and the cable and sure enough 24+v popped up.

At at this point I went on a wild goose chase unplugging everything only to find that when disconnecting the negative cable to the starter, that resolved the draw. I’m wondering it this makes sense after looking at the wiring diagram or if I need to try disconnecting the positive cable as well.

As a side note, starter works fine and has had no problem turning the engine. Additionally I tested the generator and at the batteries I’m getting about 28v while running suggesting the generator seems to be working as well.

 

[cwajciec]

It sounds like your starter solenoid is sticking on and draining the battery. Disconnect the positive cable and that should resolve the drain. If so maybe you can rebuild the solenoid? I don’t have specific knowledge of hmmwv starters so I may be wrong.

 

[NDT]

Was the ignition switch or panel lights left on?

 

[Dock Rocker]

Put a grounding harness on it and/or clean all of the grounds very well. That fixed my charging issues on my first truck.




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[papakb]

To have current draw in a vehicle electrical system you need to have 2 things, a supply point and a return point The return point in the HMMWV is the negative terminal so when you disconnect that lead you have effectively gone open circuit and won't have current flowing in the vehicle. Troubleshooting the system will necessitate the negative lead stay connected.

There is a current shunt mounted on the inner side of the battery box and you can connect a meter to test points in the STE/ICE connector to read current flow if you don't have a clampon ammeter. I'll edit this post to indicate those connections when I get a chance to look at the schematics but what your going to have to do is to look at those points as you disconnect positive leads and when the indicated current drops off or goes to zero you'll have the path of your battery drain. Clampon ammeters are reasonably inexpensive and are the best way to troubleshoot current problems but the STE/ICE test point is equally effective.

You can connect a voltmeter across pins X and W on the STE/ICE connector to read system current.

Common problem points are the control box under the dash, the diodes and regulator in the alternator and carbon buildup in the starter. Make sure the connections to the shunt itself are clean and tight. Measure the current flow and then disconnect the battery before removing or reinstalling leads to any of these electrical systems for safety and to prevent damage to the units themselves. Reconnect the disconnected lead and remeasure the current.

The heavy battery lead runs from the POS terminal on the battery to the feedthru stud in the battery box and from there to the stud on the starter. From there there is a heavy 8 gauge wire that runs up to the alternator output stud and smaller leads that connect power to the rest of the truck. The stud on the starter is a good place to start disconnecting things.

 

[Humveeholic]

Grounds are good. I went through and cleaned connections and also added the Kascar grounding kit so I’m covered there.

In in terms of the negative lead being connected, I leave it disconnected and just test current flow change after disconnecting each component. This ensure I don’t have any arching and I don’t fry any components.

To my knowledge nothing was left on as that was the first thing I checked and I’m currently seeing voltage flow when everything is off. I’m going to check amp draw today and will report back.

 

[Humveeholic]

So does anyone know if a solenoid for the injection pump should activate when connecting the negative terminal? Also I noticed that the voltage regulator on top of my 200A alternator does a slight click as well. I have confirmed that my smart box is toast which I had anticipated when I wasn’t getting a wait light or power to the plugs. Going to have to order a new set this weekend.

Lastly, while diagnosing I found that my KDS box was matched with a Nartron TSU. I thought it wasn’t recommended to mix the two...

 

[NDT]

Solenoids should not come on with ignition off.

 

[papakb]

As NDT says, the #54 lead to the IP should only have power when the ignition switch is turned on.

Remember when installing and removing electrics in the HMMWV you want to have the batteries disconnected for safety. I know this may sound repetitive but there are newcomers on these forums every day the way these trucks are selling.

 

[Humveeholic]

This is what I thought. I have had the rear battery negative post disconnected the whole time. I am not connecting anything unless the negative post is disconnected. The only time I was connecting the negative cable was to identify the source of the solenoid clicking. I haven’t tested the solenoid clicking with the control box disconnected but I’ll probably try that tomorrow to see if it may be the control box causing the issue. The only other component I can think of testing would be the ignition switch.

 

[papakb]

The IP solenoid does get it's power from the control box (engine connector A) but it's on a straight through connection (body connector B) from the ignition switch.

 

[Retiredwarhorses]

So does anyone know if a solenoid for the injection pump should activate when connecting the negative terminal? Also I noticed that the voltage regulator on top of my 200A alternator does a slight click as well. I have confirmed that my smart box is toast which I had anticipated when I wasn’t getting a wait light or power to the plugs. Going to have to order a new set this weekend.

Lastly, while diagnosing I found that my KDS box was matched with a Nartron TSU. I thought it wasn’t recommended to mix the two...

That tid bit of info on the start box and glow plug lamp not eliminating would have moved this diagnosis ahead quit quickly.

 

[TOBASH]

After reading through this thread, seems like RWH hit the nail on the head.

It seems you're a new member here and perhaps entirely new to HMMWV's/M998's.

WELCOME!

The protective control box / PCB, when not properly functioning, will "kill" the vehicle, turning it into a paperweight. That implies this might not be a battery issue.

You need to match the glow plug controller, UNLESS you have a KDS GREEN LABEL PCB BOX. KDS GREEN does NOT need glow plug controller IIRC, so you can put anything there.

Which KDS box are you running? I suggest you take a pic of the label and post.

If your green box fried, you need to replace with a matched set of PCB AND Glow Plug Controller.

[EDIT] - He has a KDS Yellow.

 

[Humveeholic]

Thanks guys. Rather than assuming I’m always one to confirm the issue at hand hence why I have gone through so many various tests. Today I confirmed that when connecting the batteries with the box completely out, Im no longer hearing the solenoids activate which suggests that the burnt out box was not recognizing the ignition switch. I am getting just a very slight spark on the negative post when connecting the cable which suggests something still may be drawing power but at this point I’m just going to replace the box and go from there.

Here is the box I pulled out

 

[TOBASH]

Over time, posts to photbucket die, and we're left with links in threads that go nowhere and get confusing.

I have taken the liberty to upload Humveeholic's pic to the site.

In general, posting to the SteelSoldiers site allows pics to remain "forever."

 

[TOBASH]

As promised in my PM, I found the link about several glow plug controllers being OK with several PCB's.

Read the first and second post on this excellent PCB explanation thread.

https://www.steelsoldiers.com/showthread.php?164930-PCB-EESS-SmartStart-S3-i-pics-info

 

[Humveeholic]

Thanks for the link!

 

[TOBASH]

Thanks for the link!