Super Duty & Heavy Duty1999 to current Ford F250, F350, F450 and F550 Super Duty with diesel V8 and gas V8 and V10 engines
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You have to give the computers time to shut down, as well as the battery saver relay so your door and hood lights are out. Otherwise you're going to get a high reading.
When I'm testing for draw, I hook a jumper wire between the negative cable of one battery and it's battery post. Then unhook the other negative cable. Wait about an hour for all the computers to get shut down and for the hood and dome lights to go out. Connect your DVOM and then remove the jumper.
If for any reason you completely disconnect power, when you reconnect it all the computers will come up live and the dome and hood lights will come back on and you'll have to start over.
2004 F-250 SD, 4x4 FX4, 6.0L PSD
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And after 45 minutes or so the current goes down to 0.05A...
However, I was measuring this at the driver side with the passenger side battery unplugged on the negative.
When I plug the passenger side battery in, I get a draw of 0.2A, 4x more! :S
(With the amp meter still on the drive side battery)
I've done another test, woken up the truck, plugged in the lamp on the hood...
I get a reading of 0.28A with two batteries plugged in and 0.88A with only one battery plugged in. :S
If the two batteries are parallel shouldn't the current just be double with 1 battery?
Any ideas on what I should test first at this point?
Un-hook the alternator cables and see what you get.
There is a plug and a cable. Also if the battery's
are not at the same state one will draw from the
other. This is why you replace them as a pair and
not one at a time.
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