I just thought of something. If I use either one of the clamp on meters I think that would eliminate the need to disconnect the battery cable to connect the leads. If that’s true, could someone give me an idea where the trunk light switch is? If I can hold that closed with a clamp or jumper around it, I’m hoping I could leave the trunk open during the test.?....

 

The trunk light switch is on the bottom edge of the trunk lid, several inches to the right of the latch. It has a rubber bellows over the plunger.

If you can't get a clamp on there, you could probably hold the plunger depressed with some strong tape. With the plunger retracted like that, raise and lower the trunk lid and make sure the light stays off. The harness to the light switch follows the right hinge arm and has been known to get damaged due to flexing at the pivot point.

Also, be aware the switch does not control the light directly. The switch provides an input to the Rear Electronic Control Module (RECM), which in turn operates the light via a switched ground.

 

Will check that all out tomorrow morning...almost my bedtime here. Thanks for the quick reply

 

The trunk light will time out too so I never unhook it because that "might" be where your problem is?

What I want when chasing current draw is to have the car in exactly the same condition as when I am driving it. Plus I really want to see the shut down happen too.

I like that PDI CA-60 but it only goes down to 10 Ma which is probably good enough?
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Driving? Don't you mean the same condition as when parked?

I will have to play around with my CA-60. I could have sworn it measured down to 1 mA, but the datasheet says otherwise. I'll have to play around with it this weekend. Maybe it can go that low, but isn't really accurate in that range. It may be adequate for a relative reading, though, when comparing two circuits.

 

Oops! Yes when parked and shutting down. Sorry about that!

Post back about the CA-60 because I have a Fluke too and was not aware of that add on device before I got the CM100.
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I was wondering about that also, thanks for the clarification. I ordered a CM 100 yesterday my trusty old fluke is about worn out and I thought I should go with the self contained unit. Will post back when I get it and run the current draw test.

 

Had a little free time today so I put on my lab coat and grabbed a clipboard. Indeed, as specified, 10mA is the lower limit for the CA-60. Below that, it was just too wonky. In fact, I'd say 20mA is a more practical lower limit for the CA-60. It would appear the CA-60 is still adequate for running quiescent drain tests (35mA range), but the CM100 is probably more accurate.

The amperage readings were confirmed with a Fluke 83 and my ancient Simpson 260. No guarantee they were accurate, but they both agreed with each other.

 

Thanks Karl!
Good to know different options and you did the research.

That was my complaint for all the meters I looked at. It is very useful to get down to that 1 Ma range so you can see everything the car is doing.

I did have some errors operating the CM-100. Be SURE and hit the zero button every time before you take a measurement. I had unrepeatable results at first and thought I had a bad meter.
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I Got the CM-100 meter yesterday and ran the test today with the following results:

car was locked overnight before starting.
unlocked and opened trunk, trunk light on
first reading was 2.025 amps
taped tunk light switch closed relocked car and reading dropped to 1.235 amps, left in this condition
5 minutes later read .712 amps
35 minutes later read .022 or 22ma
1 hour later read 26 - 28ma reading held at that level for another hour.
after

 

Try using the Peak Hold function to capture any intermittent increases:


"The PEAK HOLD function is enabled by pressing the HOLD/PEAK button until the P indicator appears on the screen. When in this mode, the instrument will hold and display the highest reading obtained during the measurement. To exit the peak/hold mode press the HOLD button for approx. 2 sec. until the display indicator turns off."


From section 4.6.2 here:

http://www.gtc.ca/pdf/manuals/CM100EMN-EN.pdf

I vaguely remember somebody else had an intermittent drain issue and the culprit was the power seat module. It would periodically power up for a few minutes but kept repeating itself, eventually killing the battery.

The Peak Hold function should work perfectly to capture something like that. I wish I noticed that when shopping for a low amp probe. It's not quite as good as a Min/Max feature, but it will still capture high readings.

 

I’m going to set it up before I go to bed and check the results in the morning, will let you know what happens. Thanks.

 

From the readings above the car is OK and has no unexpected drain.

For the sake of anyone else reading: you can use an ordinary meter and can change scale if you first short out the meter, then change scale, then remove the short (think it through).

If the car has a drain problem it appears not to have been present during the recent tests. Sounds worth using the peak hold feature once the readings have reached the 22mA kind of figure.

 

I set the car up for sleep mode last night and waited an hour. . Waited until car was in sleep mode and measured about 22ma again with the CM-100. Then I set it up to not power off and hold peak reading. After about twenty minutes I checked and read .06 or 60ma. I left it that way for another ten hours and the reading never went any higher. This morning I changed the mode to normal reading and took another reading of 19ma. I did notice that when I changed the meter to read peak current it switched to a higher scale in anticipation of readings in excess of 1 amp I suppose. I don’t know if this changes the accuracy or anything but I don't think so. Maybe in the ma range it’s more accurate at small current values then when on the higher scale . Anyhow that’s not a big issue and I’m starting to think things are OK and if I have another battery drain issue it may likely be from another source. I plan on trying this again a couple of times to see if I get repeatability in the readings.

i thought about the idea of shorting the meter out while changing scales when you have one physically connected in series and that sounds like it would work. I’m going to try that too so I can have more then one way to look at things.

thank you all again for all the many responses to this issue, and I promise I won’t beat a dead horse over it, but if you hear of anything that might be good info, please let me know. I feel like I’ve learned a lot while working through this.

Bill M

 

Bill,

Check out this method for reading small current drains. It's a long video, but the guy explains the procedure very well:




The fuses don't need to be removed. All you do is measure the minuscule voltage drop across the fuse, and convert that reading to milliamps per one of these charts:

Fuse Charts Download


Please note the chart lists different values depending on the fuse size, so you have to make sure you're reading from the correct column. I was very skeptical about the accuracy, so I set up a test circuit on my workbench, complete with an inline milliammeter. Dang if this method wasn't right on the money every time, within 5%. I was impressed. I even tried different brands of fuses and that did not affect the accuracy at all.

All you'd need is a voltmeter capable of reading millivolts. I initially tested with my trusty Fluke and then I got to wondering how a cheap meter would do. Much to my surprise, a $20 meter (GB Instruments GDT-190A) worked just as well to read millivolts.

 

+1

Though it's hard to convince some people that it works.

 

Just watched the video twice and printed the charts. This is a really great way to check things out. I’m going to do that tomorrow just to compare some readings and see what I get. Thanks for the really informative link.

on another subject, have any of you ever changed out the rear view mirror.? From what I see it looks pretty tricky. I have the mirror with compass and rain detector. I looked but couldn’t find too much in the threads, but I’m pretty new to navigating through them and may have overlooked it.

Bill M