My M998 still draws power from battery when all is turned off. How to trace it?

[vinhvinny]

I am fixing my friend's 1990 M998

I turned ignition switch, lights, heater all off.

But the truck still draws 1.7A from the battery at all time.

A guy at Advance Auto Parts store told me to test at the fuse box to see what part of the truck that draws current then fixt that part.



Does 1990 HMMWV even have a fuse box?


Or how do I trace down where it draws power? what are the common parts of the truck that would do this?

thank you

 

[NDT]

No fuse box on the HMMWV. You will have to disconnect circuits until the load goes away. I would start with disconnecting the sense wire at the alternator. Next, disconnect the connector from the light switch. If you still have draw, the protective contol box is suspect.

 

[Digger09]

Not a HMMWV but I had a similar problem on my m35 and it was a problem on the regulator on the alternator. It charges fine but would draw the batteries down when i let it sit for a week or two. I installed a battery disconnect switch since I wanted to do that anyway for security and I have no more issues.

 

[gcbennet]

My S3 box was continuing to draw power when the switch was off. I suspect a stuck relay inside. The way I learned the box was the culprit was when I reconnected the battery cables after re-charging and I heard the audible clink of the box as soon as the negative terminal made contact with the battery post. The problem was only solved when I replaced the box.

 

[ThunderSquirrel]

Not a HMMWV but I had a similar problem on my m35 and it was a problem on the regulator on the alternator. It charges fine but would draw the batteries down when i let it sit for a week or two. I installed a battery disconnect switch since I wanted to do that anyway for security and I have no more issues.

Battery disconnect was one of the first things I did for security. Got a pretty cool one that is controlled by a key fob. Makes it super easy to turn it on/off.

 

[vinhvinny]

Battery disconnect was one of the first things I did for security. Got a pretty cool one that is controlled by a key fob. Makes it super easy to turn it on/off.

now that is modern. Can you tell what brand it is?

 

[ThunderSquirrel]

The one I have is called Battery Brain Gold. Simple install like any other cut off, too.

 

[orgnal]

The one I have is called Battery Brain Gold. Simple install like any other cut off, too.

I am seeing 12V ones online; Is that what you used or did you find a 24V one? Do you have a 12V setup or 24V setup in your HMMWV? Thanks.

 

[DrillerSurplus]

Not HMMVW, but I had a small electric drain I chased for a month on a Ford F350 with the 6.0 diesel. One morning it had been sitting overnight and i happened to touch the alternator as I was tracing wires. The alternator was quite warm to the touch- problem turned out to be a bad diode in the alternator. On the 998 the diode might be in the regulator that digger09 mentions. However, I think installing a disconnect is a good idea for lots of reasons.

 

[papakb]

Switches generally aren't voltage dependent until you get into high voltage or high current applications. The thing you have to consider with a battery disconnect switch is that it has to be capable of handling the extremely high currents that starter motors draw. This can be on the order of 100 amps on some vehicles. To avoid problems go with a good brand name like Cole-Hersey or Caterpillar , switches that are specifically designed and manufactured to take the abuse. The cheap stuff doesn't last and an electrical fire is the last thing you want in your truck. The absolute worst products I've seen are the cheapo switches with the red handles that Walmart sells and those POS' that have the green knob that mount on your battery. Avoid them like the plague.

Kurt
KG6KMJ

 

[Retiredwarhorses]

I always install BCO on ground side...

 

[Retiredwarhorses]

On another note...I've been converting all my trucks over to 200amp gens, I find them much more reliable. The regulator is a 2min job if it fails.

 

[darkturbo]

Battery disconnect was one of the first things I did for security. Got a pretty cool one that is controlled by a key fob. Makes it super easy to turn it on/off.

I was looking at the battery brain gold on amazon but it seem to be getting a lot of bad review. How is it working for you??

 

[ThunderSquirrel]

Mine has been working great. The brain portion of it is somewhat useless in this application, because there is no accessory hot wire to run to it so it can look for constant draw when the truck is off. It's really just a remote battery disconnect for me.

 

[Stein12501]

Not sure but I have the same problem. After checking it out I found I lost the draw when I pulled the voltage regulator off. Going to send it off and have them look at it. It was a rebuilt 200 amp Niehoff. Hope that's where the problem is. Good Luck!!!

 

[Retiredwarhorses]

Not sure but I have the same problem. After checking it out I found I lost the draw when I pulled the voltage regulator off. Going to send it off and have them look at it. It was a rebuilt 200 amp Niehoff. Hope that's where the problem is. Good Luck!!!

New and used regs are 50.00 on sleeze bay....the regulator is used in both the 100 and 200amp gens.

 

[vinhvinny]

The absolute worst products I've seen are the cheapo switches with the red handles that Walmart sells and those POS' that have the green knob ​that mount on your battery. Avoid them like the plague.

Kurt
KG6KMJ

Thank you for all your help. My friend took his HUMVEE home and chose to use battery kill switch option. When I get my humvee I will install and keyed battery switch regardless.

I like this switch here, it has a real key and all, price is soft too and it is small.

http://www.summitracing.com/parts/uis-8070060/overview/

it has
Voltage Compatibility: 12
Continuous Amp Rating:100 amps

it does not says anything about peak amps, but I think it would be close to 1000 amps.

is this 100 amp rating good enough for humvee with glow plugs?

what is the amp draw of the humvee when start motor and glow plugs are operating?

thanks.

vin