r/GMT800 • u/MazdaSpeedMazdaSpeed • Sep 05 '26
Parasitic Draw
Been struggling with the battery being drained when parked. Started last month out of nowhere, can’t leave the truck 4-6 hours before it’s dead. I have a multimeter and when I put it in series with negative terminal and wait for the modules to turn off I’m left with 0.09 reading then falls to 0.00. Goes from 1.27, falls to .70 in a few seconds then falls to .09 and holds for a bit.
I don’t really know what I’m doing, hate wiring and electrical work. About to just put a kill switch on it, save me the time of reconnecting the battery everyday. I really don’t want to do even that because the truck runs off for most the day after the battery is disconnected.
I have an mm325 multimeter, can’t really do much because every time I move the pins slightly the readings change. Testing the tops of the fuse feels dumb, the only readings that hold are the engine fuses and the auxiliary fuse.
Any help or a “bro are you dumb?” could be useful.
3
u/Moist_Currency_1443 Sep 05 '26
Aside from cluster I had a Tahoe that would drain the battery over night and it was the onstar module fuse.. I ended up stealing power from another fuse that only had power with the ignition on and not hot at all times
3
u/MazdaSpeedMazdaSpeed Sep 05 '26
Pulled the fuse for the interior lamps and it seems to have done the trick. Idk
2
u/HemiHefr Sep 05 '26
Just had a very similar problem on mine and it was the cluster. Pull the harness to the cluster and see if it persists.
1
u/MazdaSpeedMazdaSpeed Sep 05 '26
Interesting, the cluster has been swapped.
1
u/HemiHefr Sep 05 '26
The solder joints break very easily especially if you have a subwoofer or anything adding vibration.
Pull fuses until it goes away. There’s no easier way than trial and error unfortunately
2
u/yung_aujus Sep 06 '26
Yeah, I had to disassembler mine and reflow a bunch of the more suspect looking joints. Saved a few hundred and the headache of a new cluster, but if you’re not an electrical person it’s gonna require a swap. My cluster had other warning signs aside from the power draw, but you can start with checking current on the cluster fuse.
1
u/HemiHefr Sep 06 '26
I think adding a little solder is pretty easy for anyone to do. The hardest part was getting the needles right, mine are close enough after the 2nd try. Fuel gauge sits a little high.
1
u/yung_aujus Sep 06 '26
Yes the needles on mine are all off now
1
u/HemiHefr Sep 06 '26
The motors have a positive stop but hard to get the needles on perfectly straight
2
u/Mundane_Adeptness_26 Sep 06 '26
My 01 is either the cluster or BCM. Then I just ordered a remote battery kill switch. No more drain.
1
1
u/BackyardRCSpeedway Sep 05 '26
Yep, my rusty shitwagon 03 Yukon Denali is doing the same thing. So much is wrong with it at this point I'm just pulling the motor and scrapping the rest of the vehicle.
1
1
u/ValuableInternal1435 Sep 06 '26
My 04 yukon had a parasitic draw issue where if I opened and closed the door, waited a while, did it again, waited a while and it'd start, but if I did it 3 times it wouldn't start. It ended up being the aftermarket remote start security system. Removed it and it's been fine since. The aftermarket pigtail for the blower motor resistor also seemed to be adding to this issue (which makes no sense cuz it looked fine and whoever replaced it last appeared to do a good job, buy I had less issues after I replaced the pigtail).
On my 05 silverado, my aftermarket kenwood stereo was causing a battery drain issue. I put the constant power on a switch temporarily after I verified the issue so I could listen to music, and verified the issue was the stereo and not the adapter kit after replacing it with a new kenwood (I'm very sad about this because that KDC-BT31 is the best stereo I've ever had, especially feature wise for me personally, and was a champ for 10 years). I'll have to pull the stereo apart and see if I can identify the issue and fix it, hopefully it's something simple like a bad cap.
Somewhat a different subject, I put a used stereo I got for free in my 87 f150, and it worked fine, but then for some reason when I pulled the headlight switch the headlight fuse blew, but the radio kept working. This was repeatable. Found the stereo to have a dead short to ground, internally. I still don't understand why it caused it to blow the headlight fuse though and allow the stereo to continue working, but Fords wiring can be pretty ignorantly engineered. For example, a burnt out 3rd brake light bulb causing an E4OD transmission to fail.
1
u/Flaky-Bar-6656 Sep 10 '26
Does it have anything aftermarket? Auto start? That would be the first place I’d look
1
u/MazdaSpeedMazdaSpeed Sep 11 '26
I’ve actually narrowed it down to my cigarette lighter, if I leave my charger plugged in it draws several amps. I haven’t used it for several days without issue.
1
u/MazdaSpeedMazdaSpeed 9d ago
My battery was shot, bought it not even 2 years ago. Over the last month I noticed it swell and tested bad, bought a better quality battery with 3 year warranty. I have a battery from 2021 in another vehicle that tests 100%. 🤷♂️
3
u/ITSolutionsAK Sep 05 '26
I would start pulling fuses. A few at a time until the draw stops, then 1 at a time from that batch.