Author Topic: Parasitic draw need help.  (Read 898 times)

Offline square81

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Parasitic draw need help.
« on: June 15, 2020, 09:14:00 PM »
My 81 gmc 1500 after sitting for a few days to a week will have a weak battery or even dead one. Charged battery and checked the basics. Used a test light between the negative cable and battery. It lights up so it means i have a draw. Start pulling wires for the radio memory,tach and alternator light still on. Pulled fuses and found when the horn-dome fuse is removed light went out. Removed horn button, horn relay, dome lights and cigarette lighter. Still test light was lit. Even checked bulk head connector it looked good. Wiring looks good just not sure what im missing. Sorry for the long story. Thanks

Online bd

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Re: Parasitic draw need help.
« Reply #1 on: June 15, 2020, 09:38:31 PM »
How brightly does the test light illuminate?  Is it brighter when you connect the test light across the battery terminals?

1980/81 Wiring Manual

The HORN-DM fuse also protects the two BAT power taps at the bottom of the fuse box.  Does the horn work?  Does the power draw diminish if you unplug the horn relay?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline square81

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Re: Parasitic draw need help.
« Reply #2 on: June 16, 2020, 02:11:30 PM »
Hey thanks for responding. Horn does work yes.Light is dimmer then if it was across the battery. I did pull the horn relay and it stayed lit up. Now that you mention it protecting the bottom 2 batt +. I do have a couple accessories plugged in those. Will unplug and report back. Thanks

Online bd

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Re: Parasitic draw need help.
« Reply #3 on: June 16, 2020, 02:57:33 PM »
Light is dimmer then if it was across the battery.

This tells you that the parasitic draw is less than the draw of the test light you are using.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline square81

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Re: Parasitic draw need help.
« Reply #4 on: June 16, 2020, 09:21:19 PM »
I checked the wires i had plugged into those protected circuits. Pulled the memory wire for my stereo. Light went out. I understand that it needs power for memory. But i think it draws too much. I was going to put a multimeter on it but it decided to quit. Not sure how much it should draw. Surely not enough to kill the battery. Been having issues with that stereo for awhile so maybe time to get a new one. Thanks for the quick response.

Online bd

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Re: Parasitic draw need help.
« Reply #5 on: June 16, 2020, 10:33:26 PM »
A few milliamps.  You could leave the memory wire disconnected for a week to see if the battery stops drawing down, no?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Online JohnnyPopper

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Re: Parasitic draw need help.
« Reply #6 on: June 17, 2020, 12:45:22 PM »
That shouldn't kill or weaken a battery that's in good shape.

How old is it? Have you had it tested? Are your terminals clean/solid?

Finally, you can test amp draw if you find another VOM meter that works. Like bd says, it's pry tiny.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Online bd

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Re: Parasitic draw need help.
« Reply #7 on: June 17, 2020, 02:06:08 PM »
Just a thought.  Replace the battery in your meter or the ammeter fuse if that's all that is needed.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline square81

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Re: Parasitic draw need help.
« Reply #8 on: June 21, 2020, 01:38:47 PM »
Hey guys. Getting a new meter this week to try  testing again. The battery is a interstate that is maybe 3 years old. But i take it out in the winter when i store it. It does check out good. Ive been having issues with that radio in the past. So its a good excuse to buy a new one. But will perform tests before replacing. Thanks for your responses

Offline 1978C201964

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Re: Parasitic draw need help.
« Reply #9 on: June 30, 2020, 10:02:20 AM »
I placed a quick disconnect on my battery so I would not have to keep unhooking it. $25.00 at advance auto. It will save you time and aggravation.

Online JohnnyPopper

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Re: Parasitic draw need help.
« Reply #10 on: June 30, 2020, 12:26:40 PM »
I would find it time consuming and aggravating to have to turn a switch, just sayin... :(
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline square81

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Re: Parasitic draw need help.
« Reply #11 on: July 11, 2020, 08:24:49 PM »
Hey guys sorry for not getting back to you sooner. So i got a better meter. Did my draw test and found the radio is the culprit. Its drawing too much. Cant remember forsure what it was. when i left it unhooked for a few days and also charged it fully. Didnt have any issues after. I asked a friend that's big into stereo stuff. He said some decks have little capacitors that will fail over time causing issues. My cd player is old so i dont have any issue replacing it. Will be replacing it soon. Will give an update after install. Thanks for all the input.

Online bd

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Re: Parasitic draw need help.
« Reply #12 on: July 11, 2020, 11:33:49 PM »
Thanks for the followup.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)