something draining battery 98 F150
 

hi, noob here with some strange problems on a 1998 F150 SC 4x4 Lariat (77K miles) that I bought new back in late 97.

I've been having an issue with the battery not holding a charge.

I haven't completely ruled out a bad battery yet but it was purchased new in 2/11.

The alternator seems to be ok as I'm getting about 14.2 volts at the battery while idling.

So, I decided it must be a dead short somewhere draining the battery. I disconnected the neg battery cable and clipped my test light the battery and touched the probe to the cable end - with the truck off, the test light burns bright.

I started through the process of pulling one fuse at a time - only had to pull 8 fuses before I found the culprit.

In the main fuse box under the hood, fuse 6 seems to be the culprit. When I pull it, the light goes out and stays out.

The owner's manual says that fuse is for the "Radio, Premium Sound Amplifier, CD Changer". I've left that fuse pulled for now but have no radio and am going to see if my troubles go away.

Later, I'm going to check further - the wiring diagram I have shows 3 fuses for that system - looks like past this main fuse is one that powers the head unit, and one that powers the amp and CD Changer.

So, has anyone encounter anything similar?

Can anyone tell me where the Premium Sound Amplifier is?

Is there any place I can download a service manual for this truck?

Any thoughts are appreciated!

regards,
Mike

Sounds like a bit of flawed checking.

If you unhook the battery, and rehook it back up right away, you need to let the system time out for the items like the battery saver circuit to time out and shut off. You need to have the door open for this to happen, else when you open the door it will start over again.

The BJB fuse #6 is hot all the time to the radio, for functions like radio settings, and this is also power to the factory CD changer so the cartridge can be ejected .

If the battery will not hold a charge, you might want to try a DIY check on it over night if you can.

unhook the battery from the truck ( can leave in or put n the garage ) and use a charge to fully charge the battery.
Use a meter to record the reading, should be ~ 13.2 V, let sit for 3 hours, check again, should be ~ 12.9 at the lowest this soon.

Let sit for 4 hours check again, should be 12.6 or higher.

Let site overnight, should be 12.6 or higher.

If the battery drops too fast in the 1st few hours, there is an issue with the battery, it is not the truck.

If the battery passes, that is only a quick test, the best and proper test is a load test on the battery, which means the shop will need it for a few hours to test properly.

Thanks for the reply. I am charging the battery now - will do as you suggest and test the voltages on the way down.

So, are you saying I should open the door and leave it open until the battery saver kicks in - then pull the neg cable and do my fuse testing?

This has been going on a while now, but that truck sits in the driveway 99% of the time - we use it once or twice a week to haul feed - maybe 3K miles a year - it's just a PITA when I do need it and it won't start (which seems to be every time I need it lately, lol).

[QUOTE=kernelpanic;4658033]Thanks for the reply. I am charging the battery now - will do as you suggest and test the voltages on the way down.

So, are you saying I should open the door and leave it open until the battery saver kicks in - then pull the neg cable and do my fuse testing?..<snip>...

Either you need to have the meter inline with the neg cable, and wait for the truck to go into shut down or you need to unhook the cable, install the meter and then wait.

Either way with the door open, if the interior lamps come on, the clock starts over on waiting for the testing.

I would wait on the battery testing, and if needed an actual load test 1st.

ok, so here's more on this - battery is charged holding around 12.72 volts so far

with negative cable disconnected for several hours if I stick a VM between the negative post and the cable, I am seeing a 11.34V drain

I pulled all the fuses one at a time - minis, maxis, the two in the small undocumented box near the firewall - most afforded no charge to the drain value - some dropped it to 10.68, 10.8, one to 11.08

I'm at a loss here

could the alternator be bad and causing this?

With the meter inline, did you switch to the AMP setting ?

battery sat all night with neg cable disconnected - still shows 12.66 volts this morning.

@SSCULLY - Thanks for the response. I'm just using a DMM, no AMP setting on this cheapo

I still have an 11.34V draw if I test between the neg post and the disconnected cable end

I'll keep reading and try the things I find.

I would have the battery put on an actual load test.
If it only got to 12.72 VDC fully charged after a long trickle charge, that seems a bit low to me. I would expect it to be 13 + VDC after that.

A loss of 0.08V is good, but the starting point has me scratching my head.

If you are using a volt setting from neg to the battery, that is the voltage reading, which does not show a draw.
A meter inline needs to be set to amp to find out what the draw is.
The testing is flawed.

Are you sure there is not an AMP setting, most DMM have Volt / AMP ( both AC & DC ) and at least resistance.

This is a $ 3.47 meter on amazon
http://ecx.images-amazon.com/images/...500_AA300_.jpg

This one is $ 5.99 ( not AC AMP setting, only DC ).
http://ecx.images-amazon.com/images/I/710c2t5W9fL.jpg

If you have 3 places to plug in the meter leads ( 1 for the common or black lead, and 2 places for the red lead ), it has an AMP setting.

doh, you're right - this does have that for both AC and DC - 400mA on the DC side - I'll go check that now

@SSCULLY - thank you for your help and persistence.

I think your suspicions of a bad battery are correct. There is no amp draw and the battery is down to 12.65V now (from 12.72 an hour ago). I'm in the DFW area - we had a streak of 40 days of 100+ temps - and after the next 7 days we should be around 58 days of 100+ so far in 2011

I bought this at WallyWorld, so will get the truck started and drive over there and let them check it - should still be under warranty.

thanks again

Sounds like a battery issue, testing will confirm.

Thing a lot of Yankees will confuse is the cold being the time to get a new battery, when heat will kill a marginal battery quicker than cold will.

hell, it wouldn't even start the truck - it's back on the charger now, but i may wait until Saturday and just pull it out and use the one of the other cars to take it back to WallyWorld

I meant to mention that your advice about the voltage dropping rapidly after charging was spot on - when I pulled it off the charger it was just under 14V but dropped to that 12.72 within an hour. That 12+V was enough to do my other testing (flawed as it was).

Again, thanks for the help!!

That makes sense now.
The low reading I misunderstood right after charging had me questioning what the battery was doing.

If the battery went from ~ 14 VDC to 12.7 in 1 hour, that is a sure sign of a sulfated cell ( or cells ) in the battery, and it cannot hold a charge, hence the reason why you get a dead battery within a week in the truck.

You now know 1st hand why a WallyWorld battery is that much cheaper than a brand name battery.
Might be made by the same place as the brand name, but to a different set of specifications.

If you don't care about continual returning, there is nothing wrong with it, I just don't care for the roll of the dice chance that the battery will be dead at 02:00 AM in the rain..

Brand name like ?

The battery I replaced back Jan 2011 (previously said Feb, but found the receipt) was a WallyWorld that lasted 6.5 years, but I might have just been real lucky with that one.