problem with dmm
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=104061
Printed Date: May 11, 2025 at 5:56 PM
Topic: problem with dmm
Posted By: nayr747
Subject: problem with dmm
Date Posted: April 17, 2008 at 4:08 AM
Ok, while trying to find my drain on my car battery from my alarm system, I'm having a problem getting the dmm to test the current being drawn. I set the meter to 10 Amps, put the red lead in the 10A DC port, black in COM, disconnected the neg. battery cable, and put the dmm in series (red lead to cable, black to post). I get no reading no matter what scale I put it on. I did this a couple days ago a got a reading of around 0.02 Amps, but now nothing.
I tested the fuse in the dmm to make sure that wasn't the problem by putting the red lead in the 10A DC port, black in VOhmsmA port and touching the probes together to get around 0.3 Ohms. I also tested it by putting the red lead in VOhmsmA, black in COM, and touching the red probe to the 10A DC port. Doing this I get about the same 0.3 Ohms.
The only thing I can think of that could have messed up the dmm is when I accidentally had it set on 10A DC and put the red probe to the battery's pos. post and black to neg, which sparked. I know this can damage the dmm's fuse, but why would it check out then? VERY confused! I need to find this drain!
Replies:
Posted By: i am an idiot
Date Posted: April 17, 2008 at 4:17 AM
In order to check the fuse in the meter, you need to take the fuse out of the meter, put the red probe back in the other port, touch the meter leads together to get a baseline of your leads. Then put the leads on each end of the fuse. If it were not blown you should get the same reading as you got when you touched the leads together. I am banking on a blown fuse.
Posted By: nayr747
Date Posted: April 17, 2008 at 10:26 PM
i am an idiot wrote:
In order to check the fuse in the meter, you need to take the fuse out of the meter, put the red probe back in the other port, touch the meter leads together to get a baseline of your leads. Then put the leads on each end of the fuse. If it were not blown you should get the same reading as you got when you touched the leads together. I am banking on a blown fuse.
Which setting should I have it on? And am I correct that you mean put the red lead in the VOhmmA port and not the 10A DC port when doing this?
I got no different reading from any setting so I'm just going to assume it's blown. About how much are these and where can you pick them up? It's a Powerbuilt #648349 dmm and it says it needs a 0.2A 250V fast acting fuse.
Posted By: nayr747
Date Posted: April 17, 2008 at 10:32 PM
Also, why does the meter need a 0.2A fuse when it has a setting for 10A?
Posted By: i am an idiot
Date Posted: April 17, 2008 at 10:43 PM
The .2 amp fuse is for the 200 milliamp scale. Is there a much larger fuse in the meter. It will probably not be a clear glass fuse. It should be larger in diameter than an agc fuse. Yes the V/Ohm port is where you need to have it plugged in when checking the fuses.
After looking at the meter, it may not have a fuse for the 10 amp section. If you take it apart, follow the trace from the 10 Amp connector, it should go to a piece of solid wire. Look for a burnt trace on the board between the 10 amp connection and the solid wire, and then between the solid wire and the negative terminal of the meter. If you see where the trace has burnt, let me know and we can see about getting it repaired.
Posted By: nayr747
Date Posted: April 18, 2008 at 1:16 AM
i am an idiot wrote:
The .2 amp fuse is for the 200 milliamp scale. Is there a much larger fuse in the meter. It will probably not be a clear glass fuse. It should be larger in diameter than an agc fuse. Yes the V/Ohm port is where you need to have it plugged in when checking the fuses.
After looking at the meter, it may not have a fuse for the 10 amp section. If you take it apart, follow the trace from the 10 Amp connector, it should go to a piece of solid wire. Look for a burnt trace on the board between the 10 amp connection and the solid wire, and then between the solid wire and the negative terminal of the meter. If you see where the trace has burnt, let me know and we can see about getting it repaired.
There's a large piece of metal about an inch long that looks like a beefy paper clip in diameter attached to the board in two places right above the glass fuse. It has a dark copper color and it appears as though solder from one of the points it is connected to the board at has melted a bit and run down the metal. It does look like both ends may have heated up a bit. There's a clear liquid (flux?)on the board around the two bases, and some tiny black specs in it. Could this be the 10A fuse? And do you really think it's worth it to get it repaired? I think the meter was about $15. I am *ok* at soldering but I've never done boards, so I don't know if it would be a job I could do myself.
Posted By: i am an idiot
Date Posted: April 18, 2008 at 4:01 AM
If the meter only cost 15 bucks, why not try and fix it yourself. Do you have a soldering iron and some resin core solder. It is very important to not use acid core solder. You will need a decent soldering iron to be able to get the metal shunt hot enough to solder. Heat is the key. This is a video that I think is very helpful if you plan to do any soldering. Soldering video
Posted By: nayr747
Date Posted: April 18, 2008 at 7:38 PM
i am an idiot wrote:
Do you have a soldering iron and some resin core solder.
Sure do. I've got a Well P2C butane iron, and lead-free rosin core solder. I've only ever soldered car wires and diodes though, not boards. So what's the part called and where do I get it?
Posted By: i am an idiot
Date Posted: April 18, 2008 at 7:45 PM
What part? I thought that the solder had came off of the beefy paper clip. I think you just need to resolder that back onto the board.
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