Truck info:
1997 Ford F150, Extended Cab
4.6L, 4WD

I replaced the factory battery back in Sept as the truck wouldn't start. Several times since then, the truck won't turn over, much less start. Two weeks ago, I take new battery back and get a newer one. Now, it's doing it again!

Analog volt meter indicates the following:
Approximately 13+ volts with engine running.
Approximately 12+ volts with engine off - immediately after
shutoff.
Steady at approximately 12+ volts several minutes after engine shutoff.
(Unfortunately, I do not have long term at-rest voltage readings to provide).

Analog ammeter indicates the following:
Over 500mA (meter pegged) with all fuses in place.
Over 500mA (meter pegged) with all fuses and relays removed.
Over 500mA (meter pegged) with aftermarket fuse for light in shell removed.
No other "user installed" items present.

What could be causing my battery(ies) to be going dead? Why is there an over 500mA draw on my battery whilst the truck is at rest? What, with the exeption of going to the dealer, might I do to rectify this problem - Short of installing a knife-blade cuttoff switch?

This problem seems to be intermittent as the truck may start just fine for several days or, it may be dead in the morning.

Help!

-= Drained =-

 

Battery Drain 101

Disconnect 1 battery terinal, unplug hood light, make sure everything is off...

Touch the battery terminal to the battery post, if you have a spark you have a draw, the larger the spark the more the draw.

Take a test light and put it in line with the battery and terminal(SERIES), if the light illuminates you have a large enough draw to drain the battery...

Once you determined you have a drain, start unplugging, I start with things I mounted first, since these are the likely things. You can disconnect wires pull fuzes or pull relays...

Or if you have a ammeter you can monitor it while you disconnect things...

Hope this helps...

 

Mach1, et. al.:

Perhaps my first post was unclear but, I did use an ammeter and it indicated an in excess of 500mA draw with all fuses/relays both in place and with them all removed (fusebox completely empty).

Now what?

 

Leave your meter hooked up for about a half-hour after you turn off the ignition then see what the reading is. I'd recommend using a digital meter so you can see exactly how much current is being used.

Worst case, pull every fuse _one-by-one_ until your draw goes a way.

 

You may have a bad ground connection. It will not show up if you try the fuse-pull method. Check all your ground wire connections and make sure there is no rust or oxidation between them and the mating surface.

 

13+ volts while engine is running? Just how much + is it? Should actually be in the 14 volt range with engine running. 12 volt range is too low when you shut the engine off. Should be over 13 volts.

I think your alternator is gone. Get it checked.

Don't know what the normal key off drain is, but power is required to keep the memory in the radio and the computer even with the key off.

 

normal drain for "off position" is minimal. The computer and radio memory take next to nothing. They are only an issue if storing for a long time.

I'm in with Frank. It quite possibly is a bad ground.

 

The next time you find it in trouble-500+ ma drain- try unhooking the big wire at the alternator to see if drain drops to >30 0r 40 ma.
I assume the fuses you are pulling are in the underhood fuse box & that should disconnect almost everything. the alternator output runs through one of the big fuses beside the starter relay.

 

I still suspect the alternator. The battery voltage at rest and while engine is running says it's the alternator.

I'm not convinced the meter is accurate, though, in either voltage or amperage readings.

I still think the best bet is to have the alternator checked out.

 

I wonder if he's still buying a new battery every other week?

 

Have you removed the fuses in the engine compartment during your tests ??
I am leaning towards something grounding out, or something that is staying on when it should be off, like a glove box light ...

 

I'm betting on the alternator, not just for the fact that it may not be fully charging, but it is not uncommon for them to cause battery drain when they go bad. I second what redlariet says, unhook the alternator wire and see what happens.

-Jon

 

Sorry I haven't replied to all your suggestions. I've been spending spare time rebuilding my back fence. Which implies, of course that I've been using my truck. Curiously, the battery has not died since my last post.

I did manage to get a digital meter and took the time to get the
following readings:

Engine running: 14.45 volts
Engine stopped: 13.17
Stopped 1 min: 13.06
stopped 5 mins: 12.97
stopped 30 mins: 12.84
stopped 1 hour: 12.76
stopped 2 hours: 12.61
stopped 3 hours: 12.63
stopped 4 hours: 12.63

The back fence should be done tomorrow. After that, I'll do as Redlariet suggests and try a current draw test with the alternator wire removed.

Thanks again,
-= Mark =-

 

Well the voltage with the engine running is normal so that shoots down my theory, however as Ford4ever says, it still could be the alternator. It's just that with the voltages you're now posting, it's much less likely.

 

Has anyone really figured this out. I see lots of posts that start to talk about this problem, but never a conclussion. I have a '99 S-Cab and it started killing the battery after 36 hours. If I drive every day, it is OK, but if it sits a day without starting it is dead. Battery and charging system are OK. Also the Radio went DOA at the same time it happened for the first time. It turns on, volue adjusts, but nothing else lights up or works. I think it is in AM band, but not tuned to a station. Could the radio be dragging it down?