battery drain/not charging in 88 bronco

[captaincraig]

please help! my battery gauge reads below normal even with a fully charged battery. after about two hours and four or so start-ups or over the couse of a couple of days, the battery no longer has enough juice to kick the engine over. the battery gauge slowly goes down and if it reaches "the end" while the vehicle is running the engine shuts off. both of my headlights went out on me so i removed the light switch and there was no change. the battery and alternator tested GOOD. disconnecting the battery when the engine is off does no good. my guess is a short, but where do i start? also could the problem be in the wires between the alternator and battery? thanks, craig

[miesk5]

Craig,
A guess; how did you test the batty after charging?
Rec. taking it out & having Sears or AZ, etc. test it under load.
Here is some info:
http://www.forparts.com/techbosbattery.htm

Next test is:
from L, a good pal:
"Assuming the battery is good, the way the pros track down drains is to disconnect the battery positive terminal and put an ammeter inline with the battery stud and the positive cable. You can use a cheapo radio shack meter, but make sure it has a 10A or so range. Obviously, if you try to start the engine with this setup, you'll smoke your meter.

If you have a drain on the system, you will show a current flow on the meter. Generally it is a half amp to an amp, but I've seen it go a lot higher. Go to the fuse block and start pulling fuses one at a time until you find one that makes the drain go away. Now you'll be able to use a schematic to track down what's not turning off.

If the fuse box doesn't give you a culprit, remove the cables from the battery side of the solenoid. Same situation as the fuse block, one of them may give you a circuit to trace out.

It can take some time to track down drains, just be methodical and keep eliminating possibilities one at a time until you find the problem.

BTW, the test light trick isn't reliable. You ned to be able to measure the current so that things like clock power and keep alive voltage for the CPU don't throw you off."

some commom Bronco batty drains are the fuel pump relay; can "hang-up"; do you hear the fuel pump running w/engine off? if so...pull the relay & c to see if pump shuts down; pull another realy (forget which one is same rating, and insert in the FP relay position to see if pump shuts down and amp meter returns to low current draw,.
Brake lights; bad bl switch
etc.

and a bad alt; even tho it was tested good; see:
http://www.misterfixit.com/baddiode.htm

a bad alt connector plug;
http://www.nastra.com/images/tech107.htm

Ignition Switch Fires, 88-93,
1988-89 Ford Crown Victoria, Tempo Topaz, Mercury Cougar; 1988-90 Escort, EXP; 1988 Mustang Thunderbird; 1988-93 Aerostar Bronco F150, F250, F350, Grand Marquis; 1988-91 Lincoln Town Car
Number of vehicles: 7,500,000
Ignition switch could experience an internal short circuit which can cause overheating, smoke, and fire in the steering column area.
http://www.safetyforum.com/fordfires/defrec.html

[miesk5]

geez!...good thing I copied my post before I clicked the Post icon..after I typed all this in, I hit the Post icon and got an error message; asked me to sign-in again!

[captaincraig]

thank you very much. you already have been very helpful. both the battery and the alternator were tested outside of the vehicle, but it was at advanced auto so i'm going to call them now to see what kind of tests they run. the battery that came with my bronco was manufactured in june 05 and i had a spare that was out of my junked f-150 that although older, always cranked fine. i do know that nothing obvious seems to be staying on when the engine is shut off. would the brake lights stay on if the bl switch was faulty? thanks, i don't have much experience on the electrical side of autos.

[miesk5]

Originally Posted by captaincraig

thank you very much. you already have been very helpful. both the battery and the alternator were tested outside of the vehicle, but it was at advanced auto so i'm going to call them now to see what kind of tests they run. the battery that came with my bronco was manufactured in june 05 and i had a spare that was out of my junked f-150 that although older, always cranked fine. i do know that nothing obvious seems to be staying on when the engine is shut off. would the brake lights stay on if the bl switch was faulty? thanks, i don't have much experience on the electrical side of autos.

yw!

Yes, the brake lights would stay on if the brake light switch is faulty in the closed position
brake switch is on the brake pedal's linkage; also look at frayed insulation there; a lt green wire and a lt green with red wire
btw, what year is your Bronco?

Also, if brake lights are ON; also try wiggling the e'brake pedal to see if that makes the light go off.
e brake light switch location pic on e brake pedal assembly for 92-96 by 96broncoman
http://www.supermotors.org/vehicles/...840&original=1