Battery drain problem (again)

[coletrain777]

Hi guys and gals,
I am a fairly new member (slowly moving over from TDS), and I wanted to say HI and ask a few questions. My name is Cole and I currently have a 1991 f350 N/A IDI ex cab. 2wd DRW, and a 1994 F350 Crewcab, 4x4 ZF5 SRW longbed. I really like these trucks, and plan to keep the CC for a long time. It is a new ride to me (just picked it up last week) and it is great. But alas... it's got a problem. The batteries are draining overnight.

I know that I have a battery drain on the circuit that has the dome lights/ courtesy lights, odometer, door chime etc... If I leave that fuse in my inside lights are always on mo matter what. So I pull the fuse at night, and when I come out in the morning the batteries turn the starter over very slow. I have an electronic battery charger that tells me volts and battery percentage, and when I hook it up after the truck sits for a while it normally says that my batteries are only holding about a 30% charge and aournd 12 volts. The truck seems to charge fine while running, just drains after sitting. So now that you have the story, here's my questions.

1. What could be causing my courtesy light circuit to stay on???

2. Should I have any components tested (starter, alt, etc...). I live about 25 miles from Oreilly's so I cant drive back and forth more than once (hate to waste gas).

3. What tests/diagnosis steps should I do, and in what order? I am a pretty good mechanic, but a horrible electrician, so this is my worst nighmare.

Thanks for the help guys, hope to get this figured out fairly quick. Cole

 

[RockinB]

A faulty ignition lock cylinder was the culprit in my case, but that shoudn't cause the courtesy lights to stay on. Might try checking the door switchs and dome light switch. Good luck.

 

[Papabear]

Just install a night switch as a temporary measure and if you locate it right it can serve as an anti-theft device.

 

[Full Monte]

Hi, Welcome to the site,

The order in which I would attack this is first, find the power leak problem. Then, after fixing that, have your batteries checked. All these low-charge cycles may have hurt the batteries.

I would loosen the + battery terminals so they can be removed by hand for a test. Put your multimeter in "amps" position and hook it in series with the battery terminal of one battery. Measure amperes going out of the battery with the fuse in. Then measure the amps coming out of the battery with the fuse out. If you get a very low reading with the fuse out, the rest of the vehicle is not draining much power from the battery. If there is a drain from the battery with the fuse out, start removing one fuse at a time to find the other draining circuit. After doing this, and you are sure you're working on the right circuit, all you can do is start tracing down all the wires from the lights that stay on. Are they attached to the switch side of the ignition switch or the battery side? Some idiot may have worked on it before. If the lights are supposed to work with the ignition switch off, they should be on the battery side of the circuit.

Remember...all car batteries experience a drain during non-use. We call these parasitic drains. Things like clocks, radio station presets, etc. draw current all the time.

If you need to save your batteries while you figure all of this out, you can buy a couple of battery isolation switches and install them. These allow you to turn off your batteries by opening the hood and throwing a couple of knife switches to the open position. There is also a screw-contact type that I have seen for about $6 each.

 

[coletrain777]

So, I knew I had a door switch that had gone bad, but I thought there was something else draining the batteries because they would drain even after I pulled the fuse for the courtesy lights. Well... it was the door switch only, and my batteries both had a bad cell so that explains why they would only stay charged for a short time after I charged them. Thanks for the suggestions guys, this problem is whipped

Thanks for the warm welcome as well, this place is lots more enjoyable than TDS.

I will properly introduce myself and post a few pics of my truck after I take my little guy Trick or Treating tonight.

 

[tonkadoctor]

If you still have further problems. A bad alternator will cause this and is one of the most common causes of batteries draining overnight.

IIRC this is caused by a bad diode in the rectifier. The alternator will still charge and carry correct voltage when charging which is why it is overlooked and people beat themselves up trying to figure it out. Take it to a competent shop (usually NOT Autozone) to have it tested properly.

 

[coletrain777]

Thanks,
I hope the problem is fixed, I'm pretty sure it was just the batteries. After I fixed the door switch, I checked with my volt meter and I don't have any draw on the batteries (measuring between negative terminal and negative battery cable). I checked the alt for draw or irregular charging and it checked out great. Both of my batteries had a bad cell, starts before it even cranks over now