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Need help finding battery draw on 97 GMC

lagunaMS

lagunaMS

4 by drive
Joined
Nov 25, 2020
Member Number
3077
Messages
441
Loc
Dixie
97 K2500 with a 350/4L80e

Dies after 2 days of not using it. New battery 2 months ago. Alt test at auto zone showed good and was putting out 14.35v

Pretty sure the multifunction switch is bad because the CC doesn't work. Horn relay was stuck in the activated position - clicked when I removed it and putting it back in. Pulling the horn fuse cause the same clicking in the relay. Popped the steering wheel cover off and disconnected the horn wires for now to keep the relay from being constantly activated. Putting in a new MF switch in the next hour.

Disconnected trailer brake controller and some unnecessary wiring at underhood fuse box and it still died after 2 days.

The other day after I turned off the key and took it out. Hooking up the trickle charger under the hood and still heard a faint high pitched buzzing sound

Disconnected the battery that day and it killed the noise and the noise hasn't happened again but still getting battery drain.

I'm using a Craftsman 82141 multimeter. What settings should I have this on for this?

I tried googling the procedure and saw something about removing the neg. battery cable and connecting the multimeter between that and the neg. battery post and start pulling fuses to get the reading to change but I couldn't get it to work. Is there a better way?

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I'd say where I put the red dots, you can also use a test light until the draw gets too small.
tempImageh3mXKH.png
 
If there is anything aftermarket plugged into the fuse panel in the kick panel it will keep the wrap system on and kill the battery quickly. If you need to power something use the one on the firewall behind the brake pedal.
 
Put it to dc volts with the key off and start checking fuses with the tester in millivolts mode check each fuse. No draw voltmeter it goes to zero, a draw there will be a constant voltage. Once you find what circuit it is find a wiring schematic and start looking for the issue. Good luck these suck.

 
I picked up a DC clamp meter for this kind of troubleshooting.

Beware of things like GPS, satellite radio, alarm, and hardwired USB ports pulling a few milliamps all the time.
 
Pics of meter or make and model ?

I had one but it burnt in the camp fire, havent been able to find another.

TEC or something like that and it had a grey case.

u2slow said:
I picked up a DC clamp meter for this kind of troubleshooting.

Beware of things like GPS, satellite radio, alarm, and hardwired USB ports pulling a few milliamps all the time.
Click to expand...
 
Thanks I’ll get checking the fuses as mentioned.

After replacing the multi function switch everything works but now when the hazards are on, pressing the brake stops them and holds them in the ON position.

When I turn off the hazards, key off and not in ignition, pressing the brake pedal is triggering the brake relay in the under hood fuse box. I know that’s wrong so the whole situation is likely related to the brakes. Brake switch or hack fuck brake controller wiring by previous owner
 
I have a 97 Chevy also, double checked that truck which can sit for months and have zero battery drain whatsoever, the brake lights work without the truck on too and can also hear the brake relay click, at least while the door is open with the dome light on. So maybe that's normal after all and I'll see what the issue is once I check all the fuses tomorrow after work
 
I've never had luck using fuses as a current shunt. Typically you're looking for things that are drawing like 40ma, so the amount of drop over a fuse is about as much as the fluorescent lights will inductively put into your meter leads.
lagunaMS said:
I tried googling the procedure and saw something about removing the neg. battery cable and connecting the multimeter between that and the neg. battery post and start pulling fuses to get the reading to change but I couldn't get it to work. Is there a better way?
Click to expand...
see how your meter says "10a" above the one socket? fuse is prolly blown from hooking it up wrong at some point

hook it up like m92 says, defeat the door switch so the dome light doesn't stay on and start pulling fuses until the shit drops
20ma is pretty normal
100ma is bad

my bets is on some stupid aftermarket alarm, radio or remote start system
 
lagunaMS said:
After replacing the multi function switch everything works but now when the hazards are on, pressing the brake stops them and holds them in the ON position.

When I turn off the hazards, key off and not in ignition, pressing the brake pedal is triggering the brake relay in the under hood fuse box. I know that’s wrong so the whole situation is likely related to the brakes. Brake switch or hack fuck brake controller wiring by previous owner
Click to expand...
Are you sure that isn't normal? I know on some older vehicles that is how it works, in my experience. Don't know if a late 90s vehicle is "old enough" for that to be normal though.
 
skyhiranger said:
Are you sure that isn't normal? I know on some older vehicles that is how it works, in my experience. Don't know if a late 90s vehicle is "old enough" for that to be normal though.
Click to expand...
It's normal on anything where the brake lights and blinkers are red.
Compared to red brake lights and amber blinkers.
 
also, check 7 pin trailer connector. if full of nasty, will be a draw and is only on a circuit breaker.
 
[486] said:
I've never had luck using fuses as a current shunt. Typically you're looking for things that are drawing like 40ma, so the amount of drop over a fuse is about as much as the fluorescent lights will inductively put into your meter leads.

see how your meter says "10a" above the one socket? fuse is prolly blown from hooking it up wrong at some point

hook it up like m92 says, defeat the door switch so the dome light doesn't stay on and start pulling fuses until the shit drops
20ma is pretty normal
100ma is bad

my bets is on some stupid aftermarket alarm, radio or remote start system
Click to expand...
thanks, i'll check the fuses in the meter and go from there. I ripped out a mile of shitty wiring, found an amp of some sort behind the seat but it was dark so not sure exactly what it was. Disconnected that and the brake controller wiring and I will look at the wiring behind the radio after checking shit with the meter again. Considering how everything else was wired in this truck, the radio wires are likely to be fucked too
skyhiranger said:
Are you sure that isn't normal? I know on some older vehicles that is how it works, in my experience. Don't know if a late 90s vehicle is "old enough" for that to be normal though.
Click to expand...
turns out that it is, my 97 Chevy does it too. The GMC still did it after changing out the brake switch so I guess it's fine
NOODLES said:
remove ground from battery. use a test light (not LED) between negative post and negative clamp. start pulling fuses until the light goes out.
Click to expand...

NOODLES said:
also, check 7 pin trailer connector. if full of nasty, will be a draw and is only on a circuit breaker.
Click to expand...
Thanks, never thought of using a test light. I think I read 486 post about using an old headlight as a test light so I think I'll try to make one of those while I'm searching for this issue. Have some spare toyota headlights in the shed
 
The multimmeter amps fuses blow really easily. The volts will tell you nothing.


Wire up a 1157 bulb/socket to alligator clips then connect it between the negative battery terminal and negative cable. it should be very dim. If it is bright there is a big draw which is what you seem to have. lock out the dome light and start pulling fuses while watching for it to go dim. Also, unplug the alternator. they can cause a big draw.
 
DMG said:
The multimmeter amps fuses blow really easily.
Click to expand...
ehhh, I've tested glow plugs with mine
they're really slow blow on the flukes, so you'll get a couple seconds of 15a through that 10a fuse

they'll pop instantly if you go trying to check battery voltage with the leads in the wrong holes, though
 
DMG said:
The multimmeter amps fuses blow really easily. The volts will tell you nothing.


Wire up a 1157 bulb/socket to alligator clips then connect it between the negative battery terminal and negative cable. it should be very dim. If it is bright there is a big draw which is what you seem to have. lock out the dome light and start pulling fuses while watching for it to go dim. Also, unplug the alternator. they can cause a big draw.
Click to expand...
Panzer's test is a Mili-volt test across the fuse, that is using the fuse as a shunt, effectively measuring current.
The 1156 bulb is wortwhile for easy tools.
 
CarterKraft said:
Panzer's test is a Mili-volt test across the fuse, that is using the fuse as a shunt, effectively measuring current.
The 1156 bulb is wortwhile for easy tools.
Click to expand...
Panzers test wont find a draw.
 
Power probe is pretty amazing tool of this kind of work. Otherwise a bulb with a poky think on the end and check for what lights it up.
 
DMG said:
He said to set the meter to volts or millivolts
Click to expand...
well, that's how all current shunt meters work
measuring the voltage drop across a known resistance

I just haven't had any luck finding 20ma draws across a fuse with any consistency
if it is an amp's worth of draw it'll certainly show up
 
[486] said:
well, that's how all current shunt meters work
measuring the voltage drop across a known resistance

I just haven't had any luck finding 20ma draws across a fuse with any consistency
if it is an amp's worth of draw it'll certainly show up
Click to expand...
I wouldnt bother looking for a 20ma draw.
 
[486] said:
the office pukes wanna see 60ma max
so yeah, I'm poking around and looking for that extra 20
Click to expand...
I'd like to see under 50ma but that isn't always possible for whatever reason.
IMO loads that will kill a battery in two days will be obvious fuse to fuse.
 
Haven't had time to mess with the truck lately, planning on starting again tomorrow. thanks for all the tips
 
Unimportant update - this truck has been my reliable daily driver for the past 6 months. 50 miles per day and drove it to Colorado and back last month with zero issues

After removing all the wiring mess and old brake controller didn't do it, I finally just replaced the battery and it looks like that was it. We drove it to Duluth MN in January and there was a stretch of cold temps where it didn't get above -15F for about 4 days and I think that just fucked the battery too hard for it to recover

All is well now
 
Glad its sorted.


My Frontier would kill a battery every few days. Ended up being the alternator. It would charge fine but I guess it had a bad diode and would draw power back as soon as you shut the truck off. MM showed nearly 300ma draw.
 
Gots_a_sol said:
Glad its sorted.


My Frontier would kill a battery every few days. Ended up being the alternator. It would charge fine but I guess it had a bad diode and would draw power back as soon as you shut the truck off. MM showed nearly 300ma draw.
Click to expand...
When an alternator fucks up and draws they'll usually throw off enough of a magnetic field that it'll grab a small screw driver and pull it to the case, just a quicky test I do if I suspect an issue.
 
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