Need some help, On my son's 83 Bronco/302/4 speed "granny gear"/4x4 the battery keeps draining after sitting overnight. Already has a new alternator(I know the reliability of the remanufactured alternators and when the Bronco is running I can remove the positive cable from the battery with out any affect to the motor with numerous electrical componets running. When I check the voltage with or without the positive cable connected I read 16 to 17 volts"Is this correct?") and new voltage regulator. I second guessed the battery and replaced it also and still the same thing.

I just replaced one of the headlamps(low beam burnt out) and a rear brake light on this thing the last week and while checking the voltage out put of the alternator yesterday I noticed the interior lights brighten up(brighter than normal) and when I pulled the head lights on last night they went out after getting very bright. I thought that the head lamp switch or possibly the high/low beam floor switch was/went bad but I just checked them both out and they are fine. Pulled a head lamp form 76 parts truck and hooked it up under the hood today to check. It burned for just a second on high beam and then went out. Still burns on low beam.

I know that there is unlimited things to go/be wrong here with what I've mentioned so far but hopefully some one can point me in the best direction to take first.

 

With the engine running you should get 13-14 V. Not 16-17. This should also explain why the bulbs are burning out.
AL.

 

That battery's probably cooked if it ha been getting 16-17 volts, that is a lot higher than it should be.

 

Taking the wire off the battery will cook the alt diodes very quickly, you should not do this on an alternator. You could do it on a generator though.

Best to put a test lamp/meter between the battery post and a disconnected cable, then start removing fuses one at a time, when the light goes out find out all the items that use that fuse. Check all those items for power usage. If your son hase a large setup for a radio/stereo he may have a draw on a keep alive memory.

 

Thanks guys for the advice, learned a few things and will check for draw out of the fuse box as suggested. After church we went by the same parts house that we purchased the regulator from last week and exchanged it for another new one and the voltage returned to normal (13 to 14 volts).
Radio isn't working now though, it may be fried!
Hopefully the battery will be ok, it did boil some of the water out of it but its a new battery and seems ok for the time being. May have took some of the life off of it though.
The manager at the parts house did replace one of the headlamps for free and half off on the second one. Probally out of luck on the radio if it does turn out to be fried.
This is my first time purchasing a new/bad regulator and hopefully the last,but who knows I seem to have unique problems(at least it seems that way to me).

Thanks again for the help,
Richard

 

I was going to say the same thing but I use a seat buzzer hooked between the negative batter cable (disconnected) and the negative post of the battery. With the parasitic drain going on the buzzer will buzz, when you are under the dash pulling fuses you can hear when it stops (just like the light going out) and you dont' have to get out from under the dash to look at a light with each fuse pulled.

 

This is a good idea so long as you pick a very small buzzer. That is why a testlight is normally used, because it is usually a small lamp.

Lets take the simple case of the dome light being on, draining the battery. When the negative battery cable is taken off, and the testlight is put inbetween the negative wire and the negative battery post, the testlight will light, as well as the domelight causing the drain. But the 12 volts from the battery will be shared by the testlight and the dome light(since they are now in series). The domelight being larger will have less voltage on it, a wild guess would be 3 or 4 volts. The testlight will have the remaining voltage on it, 12v-3v or 4v= 9 to 8 volts on the testlight. The testlight has a higher resistance, thus it is more sensitive to variations in circuits that have heavier loads. Get a buzzer or a lightbulb that is too big, and it will be less sensitive to circuit loads on the battery.


This is not a very good thing to do, and the "pulling the battery cable off with the engine running" test seems to get around somehow. I hope we can slowly get the info around that this is bad for the the electrical system, as you have found out. Your radio would still be working today had you not took the battery cable off. The only thing holding the system down to a reasonable voltage is the battery. The battery was absorbing all that extra energy, and that is why the water was boiling out of it. But it kept the voltage at a reasonable level. If the reg was bad, depending on engine rpm, the alt can put out well over 100 volts.

 

Good points Franklin, the seat buzzer is a very low amp draw buzzer. The battery is the buffer for spikes from the electrical system. That "battery cable off" test need to die a quiet death.

 

Thanks again,
I don't know the first time I heard to take the cable off for a test, just heard it for years but then again I didn't know about this site either. Again a great help. I called my brother this afternoon and passed it on to him about the dangers of the old pulling off the cable test. Lessoned learned!

On the good side though the radio/cd player isn't fried. It has an internal fuse which was blown and ultimately saved it.