Stupid question

[mailbox]

I hate myself for having to ask this question, but I need to know. How do I read an ammeter? I'm trying to chase down a voltage leak in my truck. I purchased one of those $5.95 multi meters from Harbor Freight and know how to use it, I just don't know how to read it. When I place the leads between the negative battery post and the battery terminal I get a 0.06 reading. What am I reading? I feel so stupid for asking this as it's something I should already know.

 

[David_Doan]

Assuming you mean you disconnected the negative battery terminal, and connected the amp meter between the negative batter post and the cable that was on the negative battery post.... your car is drawing 0.06 amps or 60 milli-amps assuming your on the amp scale. Post a pic or description of how your meter is setup and I can help you more.

Assuming everything is off, the draw should be zero. Something has found a weak path to ground. disconnect things one at a time until the reading drops to zero.

 

[Keoke]

WELL The meter HAS TWO LEADS: ONE RED AND ONE BLACK. THE RED IS PLACED ON THE POSITIVE SIdE OF YOUR POWER SYSTEM AND THE BLACK ON THE GROUND.

There are scales on the instruement marked DC AMPS which is for measuring current and you may also find one marked 10 Amps.

Set the scales first to the highest range of the Amps. If you do not know the amplitude of the current use a fuse in series with the red lead to
protect the meter if the current exceed the selected range.

Let us know how you make out.,hope this helps

 

[TR3driver]

In that case, it is showing that something in the truck is drawing 60 milliamps (.06 amps) all the time. That's actually normal for a lot of vehicles, either the ECU or stereo has memory that it is "keeping alive" with power from the main battery. It shouldn't be enough to drain the battery in any reasonable length of time (a few weeks). Of course it can be a problem if you need to store the truck for longer than that; so either disconnect the battery (which will lose your radio presets, etc) or add a solar panel to keep it charged.

Note that you need to be careful. With the ammeter connected on low range like that, any substantial load (like hitting the door locks) will likely pop the fuse inside the ammeter. Or if it doesn't have a fuse, overheat the current shunt.

As a side comment, years ago I had an Audi that would sometimes drain the battery overnight. I eventually found the problem : the relay for the rear window defogger. It was mounted under the hood and had apparently become contaminated with salt (perhaps from ocean spray). When the dew was heavy enough, the salt would conduct enough current across the base of the relay to activate it, turning on the defogger. Don't know how I would ever have found it, except we walked out to dinner one night and as we were walking back, I noticed the green indicator light for the defogger glowing.

 

[mailbox]

David, thanks for the explanation. Thats what I thought but wasn't sure of the range. TR3, I knew there is always a slight drain on the battery, however I had already taken out the fuse for the radio and the ecm knowing they would draw some. I pulled each fuse and/or relay and noticed no drop when doing so. On a slightly related note my speedometer started working again. Its an eletronic unit that had been stuck on 20mph for the longest. It doesn't work right so I may have found my problem for both things.

 

[David_Doan]

David, thanks for the explanation. Thats what I thought but wasn't sure of the range. TR3, I knew there is always a slight drain on the battery, however I had already taken out the fuse for the radio and the ecm knowing they would draw some. I pulled each fuse and/or relay and noticed no drop when doing so. On a slightly related note my speedometer started working again. Its an eletronic unit that had been stuck on 20mph for the longest. It doesn't work right so I may have found my problem for both things.

So did you find the mysterious draw?

 

[mailbox]

Not yet. Just a wild hunch.