Multimeter is not reading amps

Power/Fuel
1

I’m attempting to diagnose a parasitic battery drain on my car. First time doing it. I looked at YouTube videos, and it seemed pretty straightforward.

edit: vehicle is a 2000 GMC Jimmy
edit: multimeter is an AMES DM1000. It’s labeled as an “Electrician/HVAC TRMS Digital Multimeter.” Is the problem that it’s not an “automotive” multimeter (I realize this is probably a dumb question)?

This is a new battery (only a couple days old since my last one died due to the battery drain :weary:). I tried this 2 times–once when I got back from errands (edit: so the battery was charged at this point), and once when the car sat overnight.

So, I disconnected the negative battery terminal, got my multimeter, connected the COM and A port, and set the dial to “AMPs”

Then I set the multimeter in series. The numbers dance around a bit, then settle on 0A. I’m positive I’m making contact on the leads because there’s a spark. I tried swapping the probes to, too. Still the same issue.

edit: I also tried reading mA as well…that was also zero.

I saw online that I might have shorted out the amps fuse, but I went through the test (setting to Ohms, reading the amps terminal with the read probe). No fuse blown. Multimeter is fine.

At one point I checked voltage. It was reading about 11.7, which I realize is low for a brand-spankin’ new 12V battery (then again, I do have a parasitic drain), but could the voltage less that 12V be the issue? Like the battery needs to get over a “hump” in order to read amps?

Thanks in advance for all the help.

update: I connected the multimeter, turned on the car’s power and turned on the dome light. The multimeter then read a steady flow of around 0.2A. Something else I noticed is that whenever I tried testing mA, I didn’t get a spark with the battery leads. I tested the multimeter to determine if there was a blown fuse. The resistance reads a O.L, which I read shows the fuse is blown.

2

The amps you should see are less than 1.0 amps unless you have a massive drain. If your ammeter needs you to set the scale, you need to set it to mA to get a read. You may also have to change position of the leads. Your instruction manual for the meter should explain this.

If your battery is reading 11.7 volts, it needs to be recharged. You should be able to read some draw but who knows? You didn’t bother to tell us anything about the car or the meter brand.

Charge the battery, set the meter and wait for all the computers to go to sleep before reading the meter.

3

No, there is not a hump to get over. A couple multimeter questions:

  1. what is the minimum amperage that the meter can read? You might be reading zero because your draw is too small for your meter.
  2. Fuse: I suggest you do a direct measurement of the resistance of the fuse. I did not understand what you tried.
  3. With the meter in series, turn on something like a dome light. Then you know for sure that there is a significant current. If your meter automatically adjusts to the correct scale, turn on the headlights. Make sure you understand what scale it then sets.
4

  1. The manual says the DC current range is 660uA, 6600uA / 66mA / 660mA / 10A

  2. A commenter on this site showed how to test a shorted fuse. I basically did that.

  3. Good suggestion. I think I’ll try that next.

5

Thanks @oldnotdeadyet

I connected the multimeter, turned on the car’s power and turned on the dome light. The multimeter then read a steady flow of around 0.2A. Something else I noticed is that whenever I tried testing mA, I didn’t get a spark with the battery leads (I connected the probe to the mA port and set the dial to mA). I tested the multimeter to determine if there was a blown fuse. The resistance reads a O.L, which I read shows the fuse is blown.

I just go the multimeter and I don’t remember even being able to read mA off of that thing. So either I blew the fuse on 1st use or it was a dud device, I’m guessing?

6

What does “turned on the car’s power” mean? Does the dome light work with the key off?

Note that the 0.2 A should also be readable on the 660 mA scale.
The multimeter manual should say something about the fuse (or fuses).

1 Like
7

I turned the key in the ignition without turning on the engine. I suppose I could have turned on the dome light without turning the key. But I when I connected the multimeter to mA, I wasn’t able to get any power in order to turn the ignition or turn on the dom light.

8

Just to chime in, I’m sure a multi meter is fine but I’ve only used one for ohms and volts. To test for a parasitic drain I just used a cheap test light. Dim, no problem, bright, got a load on that circuit. Now just to throw cold water on the whole thing, you can have an intermittent drain. Had the car parked for maybe half a day. Battery was dead. Got it home and hooked up the test light and pulled fuses and everything normal. Then while scratching my head, the light went bright. Traced it to the $300 electronic level control that was partially fried. Just disconnected it. Another one I couldn’t figure out until went out in the garage one night and the dome lights were on. Seemed like a problem with the door handle button turning the lights on. Disconnected. No meter needed. Lights just didn’t turn on anymore when I pushed the button to open the door.

Just saying, even if you get the meter working, it can be a long and circuitous route to finding the problem.

9

You must have blown a fuse in the mA portion of the multimeter. You are not getting any current whatsoever through the multimeter when set on mA, so the dome light does not light. So, you need to diagnose the multimeter.

10

Also, get your battery charged, due to the low voltage reading. (It won’t cure your mA scale.)

11

When you disconnect the battery, all of the line capacitance starts to discharge. When you reconnect, there will be a large in-rush current because of all this capacitance that needs to be re-charged. Put your meter on milliamps (after replacing the fuse) and make all of the connections except the final connection to the battery. Now insert an additional shorting wire across your meter leads, then connect the battery. This will allow the in-rush current to dissipate without affecting your meter. After at least 15 seconds, remove the shorting wire and read the milliamp draw on your meter.

Many of the systems on the car will be powered up and the reading will be high. Over the course of several minutes, you should see the current drop as each one goes to sleep. After perhaps 5 minutes, you should be at the minimum draw.

1 Like
12

The OP started by saying he was investigating a parasitic drain/ I am reminded that a bad battery can lose charge and appear to be a parasitic drain. The battery should be tested, since a failure in hot weather is common.

13

Thanks. It’s actually happening on every battery I’ve had so far. The drain appears to be getting more “aggressive,” too. It’s like at first I barely noticed, but now if I don’t turn the car on for a couple of days the engine is very slow to start (if it starts at all), especially on cold days. I’ve been through 2 batteries so far noticing the battery drain. Just have a lot of life circumstances pop up which hasn’t allowed me to go through this process until now.

But I think I need to replace the fuse. Lucky me chose a multimeter with a mA fuse that’s VERY hard to find (1000V/600mA). It’ll be a couple of days until I can replace the mA fuse. I can’t even find the correct one on Amazon.

15

As others have mentioned, you need to have your battery fully charged to accurately measure a parasitic draw. Also, anything over 50mA (.050A) is too much.

16

Thanks. Dumb question, but wouldn’t running the engine a while fully charge the battery? I don’t think I have another way to do it. I live as a tenant, but I’ll see if there’s a way to hook up a power cable or something. If that’s the case I already did try testing the amps with an already-charged battery and got 0A.

17

Feel your pain. Some of those cartridge fuses for meters can be quite difficult to find unless you go through an equipment supplier or the manufacturer. Crosses can often be found using Digikey, Mouser, Grainger and the like. Digikey is pretty easy to use and has fast shipping once you are set up in their system. Kind of a pain for just a fuse however… good luck!

18

Yes, but perhaps longer than you’d think. It’s an amperage over time deal. Your car battery is around 85AH capacity and if your alternator puts out 85A then running full bore might take an hour or two if the battery is fully depleted. The alternator is also trying to run the rest of the car’s electronics at this time. Bear in mind the alternator is typically not designed to run full output for extended periods like recharging a dead battery. It could be damaged doing that. But if your battery is just low, it might take a half hour drive to replenish it. Idling normally will not provide much charge if any, the alternator RPMs need to be higher than idle speed to output…

When I rented, I would have to remove the battery and bring it into my apartment or the basement storage area to recharge it using a charger. Maybe that’s an option for you.

19

You can replace it with a 500mA 250V or higher Voltage fuse for now.

Here are some fuses in the two sizes typically used. I’m not so impressed with the Voltage and interrupting current ratings of these though. I doubt the I.C. rating of the 1000V Chinese fuse is good either. 600 mA Cartridge Fuses – Mouser

You can buy a marine deep cycle battery if the discharge issue isn’t resolveded. It won’t be damaged as much by discharging all the way as long as it isn’t allowed to freeze.

20

I wouldn’t risk the DVM on a fuse that is not properly rated. Yes, it doesn’t need to be 1000V rating but the speed of the fusing action needs to match the original specification and be the proper case size to fit properly. Might as well just get the proper fuses since they are available.

21
  1. If you want to accurately know your parasitic draw, you need to charge the battery. If you just want to find the cause, it doesn’t need to be fully charged
  2. I presume you are disconnecting the negative battery lead when you are parked.
  3. Amazon sells new multimeters for $8 that should be fine for finding the parasitic draw. That might be cheaper than the cost of a fuse plus shipping.
  4. Does your manual say that the ammeter must be wired with a specific polarity, or does it show a plus or minus? (It might have a diode that causes that.)