checking your fuse box with a test light?
Mountain Pass
Joined: Mar 2004
Posts: 102
Likes: 0
From: Wilmington, NC
If you are actually testing the fuses touch the metal connector on top of the fuse (blade type) or the metal on the ends of the fuse for glass fuses with out removing. Remove to see if blown if no light, some will require key on and some are hot always.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
To check for a short, turn all systems off and close the doors and remove the bulb from your under hood light. Then, disconnect the battery negative cable. Connect the test light between the cable and the battery neg post. If you have a short the test lamp will light.
If it does light, remove the fuses one at a time. When you see that the light is off, then you have isolated the offending circuit. (Remember that the open door will cause a draw, so you need to press the door switch, possibly tape it while testing.)
If you have pulled all the fuses and the test lamp is still lit, then try disconnecting the alternator.
If it does light, remove the fuses one at a time. When you see that the light is off, then you have isolated the offending circuit. (Remember that the open door will cause a draw, so you need to press the door switch, possibly tape it while testing.)
If you have pulled all the fuses and the test lamp is still lit, then try disconnecting the alternator.
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Elder User
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From: Edmonton, Alberta Canada
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Moderator
Joined: Jan 2001
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From: Virginia
You may have a shorted diode in the alternator, causing it to draw current all the time. I am guessing you have a diesel with dual batreries? If so, take the aux battery cable off, and then take the other negative cable off and hook it up like Bdox suggested. Here's a diagram.
Mountain Pass
Joined: Sep 2004
Posts: 146
Likes: 2
try disconnecting your batteries when fully charged and let them sit overnight. then check the voltage in the morning. you may have a battery with a dead cell, which will cause the battery to lose voltage and draw voltage from the other battery.
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Elder User
Joined: Sep 2006
Posts: 561
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From: Edmonton, Alberta Canada
So basically I should get them load tested? Isn't Ford gonna go "ok we'll load test them for you, but we'll charge you 120$/hr to do it? And thats the part where I tell them to shove their batteries up their a**es? Anyways....so disconnect the second battery and run a test with the test light...and if the test light comes on, theres something drawing current, correct? So..if the light comes on, then I start with the fuse box inside the cab, and put the clip end that grounds out on something and poke the pointy part in the fuse hole?
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
No, just go back to Franklin's illustration. Hook up the test light like that and if you have a short, the light will come on. Just pull fuses till the light goes out and that is your bad circuit. If is is an unfused circuit such as the alternator, you have to disconnect that to check if the light goes out. Got it?
If the light does not come on then take the batteries to Autozone for testing.
If the light does not come on then take the batteries to Autozone for testing.
