something is draining my battery

[gnu_42]

I have a 91 4.0 and something is constantly draining my battery. Ive tested all the fuses with no luck so i am pretty sure it has something to do with the alarm or keyless entry that the truck had when i bought it. I have no idea whats going on with the alarm or keyless entry in terms of wiring so i am trying to avoid screwing around with that.

My question is...has anyone ran a toggle switch from the negative post into the cab so you can control when the battery is 'connected'

How would you go about wiring that up?

Thanks,

Billy

 

[RobbieD]

An alarm or keyless entry shouldn't be draining the battery in a truck with a healthy charging system, that's driven regularly. Do a parasitic current draw test by disconnecting the battery's negative cable and putting a volt/ohm meter between the post and cable. You should be under about 30 to 50 milliamps. The truck's radio and computer will usually draw a couple of mA's, and an alarm, even with the light blinking, shouldn't draw more than 20mA. If the current draw test is above 30-50, you should find the reason and correct it. Putting a switch on ain't really fixing it, and you'd need a real battery disconnect switch or you'll just have other problems down the road.

 

[Jason]

Do the above test and start pulling one fuse at a time and rechecking. You'll find it.

 

[MAKG]

And routinely disconnecting the battery will interfere with computer adaptation, and will flip Continuous codes on a '91. Disconnects are something you do for long-term storage or during repairs.

 

[RCC]

Hey gnu42,

Disconnecting ground definitely not good idea.
As already mentioned, it would play hell with your PCM
and you would have to reset clock/radio all the time.

For what it's worth, here is a freakin' odd ball thing I
had with my B2. Same problem as you. Sometimes
just enough power to crank. Sometimes just chatter.
Figured my old battery was going and replaced it. No help.
Finally I came out to start the beast one morning and my
NEW battery was completely drained.
Was gonna jump it off, but decided to check positive terminal
to ground resistance. Disconnected battery and took reading
with my meter. Good thing 'cause it was dead short to ground.
Turned out to be the voltage regulator.(!)

New solid state regulator and never had the problem again.

RCC

 

[gnu_42]

Thanks for all the help...

I have tested all the fuses twice and havent found the problem. I did put the meter between the cable and post with justy a light tester and it light the light up bright.

Where is the voltage regulator and how do you check it?

Thanks

Billy

 

[RCC]

Hey gnu42,

On your rig, voltage regulator is part of alternator.
Some are located on the back of the alternator.
(small box where harness plugs in)
Others have regulator built in.
Either way, if you don't have a good multimeter for
performing voltage and resistance checks, it would be
best for you to have the alternator tested.

Some parts houses in my area test them for free.
Basically checks your entire charging system.
Check your local jobbers.

RCC

 

[gnu_42]

The first thing i did when i got the truck and foudn it was killing the battery was got the alternator checked and it is charging fine.

I went and bought a multimeter and did all the tests that the haynes manual said to do, and i was getting the number the manual said i should be getting

 

[RobbieD]

OK, you said you put a test light between the disconnected battery cable and the battery terminal, right? The light lighting brightly shows a major parasitic current draw(i.e.- truck off & at rest). That ain't normal, and that's why your battery's going dead.

Put the test light back in place, and then start pulling fuses, one at a time, until the light goes out. Do the inside fuse box first, and then the engine compartment fuse box (you did check that one too, earlier, right?).

What kind of aftermarket equipment does this truck have, besides the alarm or keyless entry? More often than not aftermarket equipment accounts for an excessive parasitic current draw problem. An alarm would have to be triggered and sounding the siren to light a testlight like you describe. Is there an amplifier in this truck? If it's turn-on input is not wired right it would create a current draw.

 

[gnu_42]

yea it has an amp and subs that were installed before i bought it. I bought the truck off of a stereo installer so i didnt think it would be an issue but i will definitly look into it tomorrow.
I have pulled all the fuses twice already.

 

[Explorin94]

OK, you said you put a test light between the disconnected battery cable and the battery terminal, right? The light lighting brightly shows a major parasitic current draw(i.e.- truck off & at rest). That ain't normal, and that's why your battery's going dead.

Put the test light back in place, and then start pulling fuses, one at a time, until the light goes out. Do the inside fuse box first, and then the engine compartment fuse box (you did check that one too, earlier, right?).

What kind of aftermarket equipment does this truck have, besides the alarm or keyless entry? More often than not aftermarket equipment accounts for an excessive parasitic current draw problem. An alarm would have to be triggered and sounding the siren to light a testlight like you describe. Is there an amplifier in this truck? If it's turn-on input is not wired right it would create a current draw.

^^^^^^^^^^^+1^^^^^^^^^^^^^

 

[RCC]

gnu42,

AH HA.
You never mentioned anything about having a
thumpin' boom box in that truck. Big amplifiers
are battery eaters.
Those power amps usually have a separate
heavy gauge power lead from the battery with a big
honkin' in-line fuse. Have you pulled that fuse, yet?

RCC

 

[gnu_42]

I checked EVERYTHING again and still no luck. I even started screwing around with the alarm/keyless entry. The only way i got no power running through the light tester was to unplug the power cord coming directly off the battery into the alarm system. I think that is becuase if you disconnect the alarm it will automatically shit everything down as an anti theft mechanism right?

 

[MAKG]

I suppose it could, but it wouldn't be very hard to bypass. It's just going to disconnect the PD box or somesuch or it will be prohibitively expensive to install. Or else it just disconnects one critical system like the ignition primary or the fuel pump.

But a REALLY easy way to tell is to disconnect that alarm and crank the vehicle (with a jumpstart if need be).

I strongly discourage using a test light for this because it isn't a terribly sensitive test. Use an AMMETER, preferably the clamp-on type. If you had two 500 mA drains, you wouldn't be able to find them with a test light, but it would be obvious with an ammeter.

 

[fastpakr]

if you disconnect the alarm it will automatically shit everything

That's quite an alarm!