Battery Draw
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Trailering
Joined: Jul 2012
Posts: 17
Likes: 1
Battery Draw
I have a 2002 F-250 Super Duty 7.3. Lately I have been dealing with a battery draw which will kill both batteries within a couple days if left connected. I am currently trouble shooting that issue and disconnect each battery overnight. My question is, with winter weather coming on and I prefer to plug my truck in should the nighttime temperature be predicted to drop below 20, does the core heater still work with the batteries disconnected? I assume it does, but wanted to ask the community.
Thanks and to all, have a Blessed and Happy Thanksgiving
Tom
Thanks and to all, have a Blessed and Happy Thanksgiving
Tom
Fleet Mechanic
Joined: Nov 2006
Posts: 1,664
Likes: 219
From: Northwest
Look around your truck at night with no other outdoor lighting in the area. I had a drain happening from the glove box light staying on even when the door was shut. Hopefully it is just something simple.
Hobo
Hobo
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Trailering
Joined: Jul 2012
Posts: 17
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Thanks for the advice. I have pulled each fuse one at a time and tested. No luck. The next step would be to dump all fuses and plug them back in one at a time, however, I have a very knowledgeable mechanic friend who has said most Ford truck battery draws are caused by the radio. I may pull that first.
Lead Driver
Joined: Jun 2004
Posts: 6,303
Likes: 576
From: Amarillo, TEXAS!
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Trailering
Joined: Jul 2012
Posts: 17
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Disconnected both negative leads to the batteries. I then took a test light and hooked it to the disconnected negative lead of the auxiliary battery and the connector of the test light to the negative pole of the auxiliary battery. The light lit. I then pulled each fuse, one at a time, touched the negative lead of the battery to the battery pole to recharge the system, the light went out. Took the lead away from the battery, the light lit. Did this with all fuses and relays.
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Lead Driver
Joined: Jun 2004
Posts: 6,303
Likes: 576
From: Amarillo, TEXAS!
Got it. Do you have a multimeter or DC ammeter? If so pull both grounds from the batteries, then connect the leads of the meter between the ground cable and battery post of one battery. Make note of the current draw. Then pull one fuse at a time and see which fuse(s) causes a significant drop.
Also, how old are the batteries, and have you had them load tested?
Also, how old are the batteries, and have you had them load tested?
Lead Driver
Joined: Jun 2004
Posts: 6,303
Likes: 576
From: Amarillo, TEXAS!
Yes, the amps setting. The problems with using a test light for this are the sheer number of circuits involved and you need to know how much current is drawn and which circuits are drawing it. It's normal for some to use power any time the batteries are connected.
BTW, don't turn anything on when using the multimeter to test. You'll probably pop the fuse inside the meter or fry the leads.
BTW, don't turn anything on when using the multimeter to test. You'll probably pop the fuse inside the meter or fry the leads.
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Trailering
Joined: Jul 2012
Posts: 17
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When I set my meter to 10A on the DC scale, I get 0.01. That doesn't seem right. I tried to pull the radio, but it won't come out and I do have the tool. Looks like I'm about to dump all the fuses and go by the light. Thanks for your help.
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Trailering
Joined: Jul 2012
Posts: 17
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I have given up on the test light procedure and gone to the VOM. I am hooked up with the red lead to the negative battery pole and the black lead to the negative truck cable. I have never chased a draw like this, so I'm not sure what I am looking at, or what should, or should not, be normal. When hooked up like this, my interior light comes on and my cargo light is on. I am reading 3.00 amps. When I close the door and the lights are off, I read 0.58 amps. My question now is should these lights be on with the batteries disconnected? Is there a way to tell the truck the door is closed when it is actually open?
Any and all help is much appreciated.
Any and all help is much appreciated.
Laughing Gas
Joined: May 2024
Posts: 897
Likes: 288
From: E TN
Acceptable draw is 30 milliamps. You should use a bridge or a jumper lead so all of the items that retain power can power down, then you open the bridge or remove that lead while the amp meter is connected and you should be able to get a reading. Also be sure to check the alternator by unplugging it, it can be a source of a draw.
You can check Youtube for a video on parasitic draw if you're not sure how to do it.
You can check Youtube for a video on parasitic draw if you're not sure how to do it.