shaverjeff

94 F150, recently something started draining the battery very quickly.

If I unhook the positive cable and run a voltmeter there it reads 12.6 with ignition in any position. Does that mean there is a 12.6 draw on the battery?

Am I correct in assuming the ignition could be at fault?

I've unhooked the starter, and alt, with the same result/reading.
Pulled every fuse one at a time with no change either.

Any recommendations what to check/test next before I start pulling the ignition tumbler apart? There is a lot of slop in it and prior to the battery draining sometimes it would not cut power with the key out (buzzer would chime as though the key was in)

Thanks in advance.

Bryson

Sorry if this is a stupid question, did you mean even with key off there is a 12.6 draw?

armstrong4x4

I really don't understand the test your doing, seems to me like your just testing the voltage in the battery to me..

shaverjeff

I think you are correct, I'm not testing correctly...
I am trying to follow what is shown here:
https://www.f150forum.com/f10/batter...source-138817/

I think I need to test amps not volts from the neg terminal?

I just swapped in a fresh key/tumbler so I rule that one out.

armstrong4x4

yeah I'm pretty sure you just need an amp clamp and turn everything off and if it show amperage flowing then start pulling fuses until you find one that makes the amperage flow stop. then that isolates the problem to that circuit..

Dripper

1st guess.....there's a short,cut in the wire,its touching the truck somewhere

2nd guess.....circuit blew or needing a new relay.

shaverjeff

It appears as though the ignition tumbler may have been the culprit.
I was able to perform and amp test (correctly this time) and its spikes for a fraction of a second at 3 amps, then a relay clicks (not sure which one) and it settles to .09 amps. Previously there was a 4 amp drain all the time even without the ignition in the "on" position.

Is .09 amps acceptable for typical drain? (assuming ecu and radio memory)

Hopefully all is well, I will need to pick up a new battery as the old one didn't make it.

Is there a recommended cranking amps for the 5.0? It seems to vary from around 600-810 (cold cranking amps) Previous batter wasn't labeled.

Dripper

this is the best advice yet.keep all doors closed while checking amps cause door light draws amps/voltage.

Warlockk

0.9 amps is ok, not knowing your sound system. It's a little high but not seriously. Rule of thumb is under 1 amp.

shaverjeff

Swapped new battery and tested again.
Amp draw is actually .09 Amp (type before).
It still starts at 3amp for a split second then a relay clicks and it settles to .09.

Everything pointed to the tumbler being the issue, unless I fixed a short when unhooking the alt/starter and reinstalling.
The truck is stock except for an aftermarket stereo (no amps)

Thanks for the help!