ok 2008 F250 V10 124K
battery is 6 months old and tested fine
alternator tested fine

every morning battery is dead

Anyone have a good technique to diagnose an electrical drain problem?

 

These can be frustrating...

Put a voltmeter on the battery and start pulling fuses one at a time until you see a fluctuation.

 

To find a draw close doors and turn everything off, set your meter to amps. Put prob on one side of fuze and the other on the other side of fuze. Watch amperage if there is a draw amperage will be shown. Best to use a meter with 20 amp max. This will direct you to the fuze that is the circuit casing the draw. A word of warning don't open door or turn anything with meter hooked up. When fuze is located I use a head light old stile with two wire attached. Remove fuze and plug into fuze with spade connectors attached to wires from hight light. If head light lights start unplugging connectors on they circuit when light goes out you found the draw. Buy disconnecting batter and testing from battery and cable you can cause problems with components that may need re flash or relearn

 

Do you have any aftermarket accessories installed is the first question to ask - sound system?

You want to measure the current draw when everything is off. Should not exceed about 50 milliamps.

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You also have to take into account any battery saver delay before making your measurement. On some Fords, the delay is 30-40 minutes before everything goes to sleep.

 

Projectsh089 good point forgot to put that in my post.

 

Absolutely, it can take 30 minutes for various components to go into "sleep mode".

Another consideration is that without using a clamp-on meter, it is necessary to disconnect the battery which can cause other problems depending on the vehicle.

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I have a HitchCam and a cap with an interior light. Other than that its stock.

 

Thats a cool idea. I wonder if I can hook either ends to something that makes a sound, that way I can hear when Ive opened the cricuit

 

you can buy a circut tester at harbor freight for 15 bucks that will let you test each fuse circut one at a time....so basically with each circut off you will know if something is drawing a load.

if you want a guess...pull the fuse on the air conditioner...sometimes the air conditioner clutch draws power even when off....enough to kill your battery over night.

 

Here is the best way to check for parasitic battery drain:

 

Thanks Davidb that exactly what I was talking about!

 

You don't have to when you hook a big head light to the circuit, you can see it a mile away. Light lite complete circuit, light out open circuit. You can also use this for shorted circuit, lot better then spending $ on fuzes when your trying to find a short that keeps blowing them. Remove the blown fuze, plug in the light. get the wiring diagram for the circuit. Start unplugging or look for wire shorted when light goes out you found it.

 

ok I didnt find any voltage loss across any of the fuses.

But, I did find a severely corroded and crumbly ground strap. Could that drain a battery?

 

It would cause a higher amperage draw while you were placing large demands on the battery such as when you engage the starter, but I can't think of any way that it would contribute to a drain on the system while the vehicle is parked.