Parasitic Battery Drain will be my downfall (2016.5 CX-5)

[plr2005]

I am racking my brain trying to figure out my battery drain.
Info:
2016.5 CX5 Grand Touring
Brand new battery
Original alternator
No aftermarket modifications.

I went away for a week. I came back to a dead battery. I figured ok yea this is normal. So I jumped it and let it charge. I said ok that’s it. Then over night it discharged to probably around 12.3 v bc it struggled to turn over. I thought that’s weird it was never like this before. So charge the battery by driving. The battery never really got over 12.3 volts when turned off. I tested the alternator and I get 13.8 volts when vehicle is running. I changed the battery 3 days ago under warranty because it wasnt holding charge. The new battery after a nice drive was at 12.8 volts when I turned the vehicle off. Over night it dropped to around 12.5-12.6. So I figure this is the resting voltage. Fast forward to today and it was dead this morning. So I took out the multimeter and tested the negative in series and was getting around 1.6-1.7 amps drawn. Then I tested the voltage drop of the fuses after the computer was completely shut down, and saw 4 of the low profile fuses drawing about 4.6 millivolts all together. I pulled the four fuses and when in series the draw went down to around .4 amps. Which seems like a normal draw. The car is undriveable without those fuses. I attached a picture showing which fuses. I have yet to test the cases fuses or relays bc I’m waiting for a tool to come in instead of using pliers or the included tiny tool. In the picture the white number is the millivolts dropage. Any help will be appreciated. I will test the internal fuse box when I get home.

 

[edmaz]

Before getting into anything about those fuses, I'll ask how long you waited to start the draw test, after shutting down the vehicle and opening/closing any doors.

 

[stickerbush]

So I took out the multimeter and tested the negative in series and was getting around 1.6-1.7 amps drawn. Then I tested the voltage drop of the fuses after the computer was completely shut down, and saw 4 of the low profile fuses drawing about 4.6 millivolts all together. I pulled the four fuses and when in series the draw went down to around .4 amps.

1.7A is way too much. Try measuring the current as you replace each of the 4 fuses and see which one(s) are drawing current. Let us know the results.

 

[youri]

To be on the safe side, you should wait at least 40 minutes after shutting everything off to test for parasitic drain. A lot of systems in the car stays on for a while.

I don’t know what the load value for your model are exactly, but as an example when mazda had a parasitic drain problem with the 2020 CX-9 they issued a TSB with the following mention:

For the CX-9 2020
DESCRIPTION
Some customers may experience an engine no start due to low battery voltage. Mazda is aware of the
issue and is working on a solution.
NOTE:Battery parasitic draw is intermittent. When the condition is present, battery parasitic draw exceeds
65 mA (0.065 A) 40 minutes after key OFF.
Contact Hotline for latest repair information

 

[plr2005]

So I did the test again after waiting about 30 minutes. Took all 4 of the fuses out. Put them back in 1x1 . The ABS fuse eventually dropped drop to unde 10 mA, I put the transmission one in and that with the abs eventually settle around 30 mA . The 7.5 amp fuse eventually bottom d out as well. It’s the room fuse that keeps it at around 1.5-1.7amps When removed it will go back down to round 30-40 mA

 

[stickerbush]

The room fuse is the overhead light. Either it's turned on or the circuit is leaking current to ground somewhere.

 

[plr2005]

The room fuse is the overhead light. Either it's turned on or the circuit is leaking current to ground somewhere.

It’s not just the overhead light, it controls instrument display, key fob sensors and more

 

[plr2005]

It’s not just the overhead light, it controls instrument display, key fob sensors and more

How would I test if a light circuit is leaking to ground

 

[stickerbush]

How would I test if a light circuit is leaking to ground

If it were just a light circuit you could test by removing the bulb and seeing if the circuit still used current. It sounds more complicated though with many things being on the circuit. This being the case it's more likely to be one of the components on the circuit. Complicated. Not sure what else to suggest to troubleshoot.

 

[plr2005]

Yea I’m at a loss. I removed the map light bulbs, some light bulbs and lift game bulbs and no change

 

[edmaz]

Yea I’m at a loss. I removed the map light bulbs, some light bulbs and lift game bulbs and no change

No one here is looking over your shoulder while you do this testing, so we have to ask whenever there's any question about what you're doing. And the first question I have is if you're aware that almost anything you do, such as putting a fuse back in or opening a door, is virtually certain to cause one or more modules to wake up and cause additional draw. And when that happens, you'll need to wait once again until everything shuts down. So did you do a 15 or so minute wait, whenever you swapped the fuses in and out?

Do you have a set of wiring diagrams for your vehicle? (It's a must have for this type of diagnostic testing). And a clamp meter capable of reading DC amps can be really helpful for this stuff as well.

 

[plr2005]

No one here is looking over your shoulder while you do this testing, so we have to ask whenever there's any question about what you're doing. And the first question I have is if you're aware that almost anything you do, such as putting a fuse back in or opening a door, is virtually certain to cause one or more modules to wake up and cause additional draw. And when that happens, you'll need to wait once again until everything shuts down. So did you do a 15 or so minute wait, whenever you swapped the fuses in and out?

Do you have a set of wiring diagrams for your vehicle? (It's a must have for this type of diagnostic testing). And a clamp meter capable of reading DC amps can be really helpful for this stuff as well.

I did wait after every fuse. I waited even longer when I put the room fuse back in to see if it would drop at all.

 

[edmaz]

I did wait after every fuse. I waited even longer when I put the room fuse back in to see if it would drop at all.

Ok, so now that you have confirmed it's the room fuse, next comes the grunt work of testing everything protected by that fuse, one at a time. Using the wiring diagrams, you would either disconnect at the individual connector or check for active current in the near wiring with a clamp meter. But if you're not up for going that deep into this problem, then take it to an auto-electric shop, which specializes in that type of diagnostic work.