Stumped To This Point

Does your internal amp meter have a min/max feature? I mean if you leave it hooked up for a few hours will it record any change in current flow and tell you how high it goes? 71mA simply can not kill a battery overnight.

Do you have a thermal imaging camera or willing to invest in one? Anything that will kill a battery that quickly should have a heat signature significantly higher than surrounding circuits. I have found troublesome draws that way.

Of course it also requires you to be there during the intermittent events. Good luck with that!

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That is very, very strange and unusual. Make this problem even more “Poltergeist-ish”

It wouldn’t. A amp meter w/a min/max function (as suggested above by ASEMaster) will show you that at times the drain is much more than 71 mA. But even that won’t show you when it occurs. There are applications for cell phone cameras that will automatically take a photo every 5 minutes, might want to download one of those to your cell phone , set it up to take a photo of the meter.

Are you certain the driver’s side door switch isn’t a little flakey?

I have read somewhere about 1997-05 blazers having a drain and it was a problem with the vanity mirror light staying on even when the cover was closed. not sure if you have one. but if you do it might be a place to check even though you have a Sonoma. seems like places to look are getting slim.


None of my meters have a min/max function. No lights staying on at all including vanity lamps, etc.

There is a 6 gauge cable from the main battery fusible link and it attaches to a tab at the under hood fuse block with a single bolt. With that disconnected and checking draw at the battery there is not even a single mA being pulled. I’ve wiggled and twisted wire harnesses to see if maybe there is some internal chaffing but so far nothing. Just the 71 mA between that cable end and the fuse box tab is it.

Left it connected all day and no problem. FIred right up tonight.
That original 2+ amp draw which would drop to 700 mAs has been MIA all week. Beats me.
Speaking for myself (and I’m sure other techs lean this way also) there is a bit of an ego issue at play too. No one likes to get beat by a hunk of metal and plastic.
I could add a cut-off switch but that’s not really fixing the problem; plus it cuts power to the PCM, BCM, radio, etc.

May fish around on eBay this weekend and see if I can pick up a used typewriter. The other monkeys in the room are waiting… :slight_smile:

No thermal imaging camera but that might be an option. I just hate to invest in tools at this point in my life as I have an issue which could leave me dead 5 minutes after posting this or 20 years from now. If I don’t sort it out in a week or so I just may get a thermal camera and see what happens.
Thanks again for all advice and suggestions.

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You know you want these … lol …

Sorry to see you so stumped, the theft system suggested ignition switch problem posted earlier, now you need a cause for intermittent drain overnight, got to be something live with ignition off. Shorting wire in door jamb? Don’t remember all the thoughts, but this is going on so long, and you have years of experience. Forgive me please if needed.

Well, an update on the road to nowhere…

I have considered a cable issue but I tracked down cables a few weeks ago. Cleaned all ground connections, peeled back insulation for a look at the wire itself, and so on. Only found one problem and that was a corroded + cable near the cable end. Fixed that.

All week the truck sat with the power cable to the underhood fuse block disconnected. Hook it up; truck starts right up and drive it anywhere. (Restarts excluded…)
Last night I checked current draw again (71 mAs) and connected the power cable to the fuse block. I also disconnected the BCM and keyless entry module just in case. The truck was left like this all night.

This morning; weak dash lights (uh oh…) and a starter solenoid chatter with the battery reading 9.56 volts and still showing that 71 mAs draw. This is on the single, as fitted battery. I even resorted to pulling an identical battery out of another car here and the same thing. That identical battery or my truck battery shows no problems in the other car.

At this point I won’t say I’m beaten yet but getting close. Again, thanks for the suggestions. Gonna go over cables again but given the propensity for the battery to discharge itself when connected to the fuse block I tend to think the cables are not the problem. That original 2+ amps draw is still MIA so beats me.

if I am reading this right you have the draw when connecting the cable to the fuse box. if so, maybe there is something in the back of the fuse box that is shorting causing the draw. I have read about problems on other vehicles with problems with the back part of the fuse box corroding. just a thought

True; the draw is only when the power lead is connected to the fuse box but that draw (71 mAs) is normal and should not kill a battery in weeks much less overnight.

It’s been on the charger for over half an hour and I would bet that when I go back out in a bit it will start right up. I’ve pulled the fuse box loose and cannot find anything corroded, burned leads or pins, etc.

Well, back to the salt mines as they say. Back later.

Well, I think it is time to look at every component. I don’t know what electronic devices the truck has but like I said, I had the electronic level control on my Riv act like that. Drained the battery in no time, then was fine. Only caught it by accident. Same thing with the interior lights coming on in the garage from a rusty short in the door handle.

Something has to be activating when you aren’t around. Fuel pump, radio, lights, Maybe put a time lapse camera on the dang thing before you shoot it.

This topic is giving me a lesson in how/why it was so difficult for a mechanic to find and correct a parasitic draw problem on my dad’s used '87 Mercury some years ago.

In that case it turned out that the previous owner had had a trailer hitch plus appropriate wiring for trailering a boat. Before selling the car the owner had removed the hitch but left the wiring and connector tucked up out of sight. Fast forward several years and corrosion caused that hidden connector and/or wiring to default to always on, thereby repeatedly draining the battery.

@ok4450 Hope you can soon find the gremlin causing your problem.

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To update this dredged from the dead issue; nothing has changed. Since the truck was consuming my life and other issues were pressing more I had to back off a bit.

The oddities still continued. I’m not giving up but am stumped. The only draw is the 71 mAs and that is the power lead to the underhood fuse box. With that disconnected and draw checked at the battery the draw is flat zero.

With battery at a full charge and showing 12.8 the battery will hold that voltage or close to it for days with the underhood fuse box disconnected.
Once (fuse box connected) voltage dropped overnight to the mid 7s. This weekend after sitting for several days voltage was still in the 12s. Turn the key; fires right up and runs like a top. Drove it 80 miles over the weekend with zero issues.

That could lead to a question of the battery. It has been checked ad nauseum and is fine. Both batteries perform flawlessly in another vehicle. By the same token both batteries act up in the truck.
With a nice evening 3 or 4 days ago I pulled up a lawn chair and connected the multimeter. Sat there for a few hours reading a book while killing a bottle of wine. Nothing amiss; the same 71 mAs as always.

At times after 3 or 4 hours the dash lights dim with the key on (voltage in 11s) and there is a hint of solenoid chatter before it starts. I’ve even done voltage drop tests across cable connections and rechecked grounds. Nothing.
Right now after sitting all day it will fire right up. Tomorrow could be a coin flip. When, and even if, there is a Eureka moment I will post the result.

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I know you have not replaced the key switch, alarm light still on? Next guess intermittent short in an always live wire like the one that goes through the door jamb for the door locks etc., even interior lights. I know you are a really smart guy, and know your stuff, no offence intended

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No offense taken at all. Yes, the dash glitches still remain but that should be taken care of with another BCM which I am trying to obtain right now. The seller of the last BCM had a 1 year warranty on them and graciously refunded my money on it.
The BCM is not the cause of the battery issue though; unless for some oddball reason it decides to go stupid at 4 in the morning and pull a fast one on me.

I don’ think that is the issue though as this odd battery problem has happened with the BCM removed and lying in the seat. Right now I’m just perplexed as this is the strangest electrical problem I’ve ever dinked around with.

I thought the Fiat problem I wrestled and the Volvo ECM killed by a can of Donald Duck orange juice were headaches but they were nothing compared to my truck.

I did not go back and reread the whole post again, but I think I remember you saying you had a problem with the dash gauges or something. I remember reading a post on another forum about someone with a problem like yours. he was having a 90ma draw if I remember right. when he could not figure it out, he brought it to the dealer. after being there for a while they tracked down the problem being in the dash cluster. not sure if this is your problem but I thought I would mention it.

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Thanks for the dash cluster suggestion. I will check it out this week hopefully. I have actually considered changing the cluster anyway to a white face unit as the stock one is not very visible at night or daytime.

A few days ago it sat for 2 days unused with the battery connected to the underhood fuse box. Go out about 6 p.m. Monday evening, hit the key, fired right up and ran great. Battery before starting was at 12.6 volts.

I leave the battery connected, go out Tuesday morning, turn the key on and dim dash warning lights after roughly 13 hours.
Uh oh…sure enough, hit the start position and nothing. Battery voltage was at 8.12 volts. Current draw every time I check is right at 71 milliamps.

I’m going to keep flogging that horse until it’s dead to the nth degree. Like many mechanics there is an ego issue involved as they do not like to get beat by a problem and this one is winning in spades.

I am not a mechanic so do not have any advice for you but I know about the ego part I am pulling for you best of luck.

When and if I figure it out I will post the cause just in case there is someone else with the same issue.

I cut the security tape on the BCM and went over it last night with a magnifying glass. No burned spots, bad solder, etc that I can see but figuring out micro printed circuits would be way above my pay grade.


We’re like cats with mice aren’t we. None of us ever want to admit that there’s a problem we can’t figure out. Even when the economics of the situation dictate that it’s time to move on.

At least this is your own car, on your own time. Can you imagine if this were a customer’s car? “I’m sorry Mr. Jones, this is a really odd problem. But I’ll fix your car no matter how much money it costs me!”