I have a pain in the battery. =~(

My 1990 Chevy 2WD 350 automatic long box pickemup with 70,000 miles on it has developed a drain on the battery.

It started when the truck cranked over slowly on cold days. The battery is 11 years old so I bought a new one. Problem solved.

A week later miles from home, it wouldn't start. Click, click, no crank. I tapped the starter with a tire iron and three attempts later it turned over and got me home. (right up onto the ramps!)

Diagnosis: I pulled the ground wire from the battery. Putting a meter between the ground strap and the battery, there's still a 12 V pull. Pulling one fuse at a time, there's still a draw. I'm lost.

What is it on a vehicle that is not fused? What runs without the key? Headlights? I know the brake lights do. How do I eliminate things that need electricity?

Again, nothing has been added or changed to the truck, no new fog ights or stereos.

Thanx, Dan

What you need to check is the amp draw between the negative cable and battery post. Try your one at a time fuse test again. Also disconnect the alternator power cable and voltage reg/exciter leads. Actually I'd do that test before any others.

More than one CS series GM alternator has shorted causing a drain, I would also check stereo, ignition switch, headlamp switch and quality of cables/connections for the grounds/powers. I had a similar year Safari van in the shop the other day with a cable corroded in the middle, both ends looked good. would not keep the battery charged.

There's always going to be 12v at the battery.

The proper way is to use an ammeter, but quick and dirty, you can hook a test light between the negative cable and post. A normal radio memory draw might make the light glow, but if its on full bright, something is drawing. Remember when you go inside to check things, you are opening the door, which turns on the interior light.

Pull fuses one at a time...

First, make sure your battery is charging. On a low optioned older vehicle with a healthy battery, you can run for quite a while without a charging battery. You need around 13.5 volts across the battery at 1500 RPM and all high draw accessories on (high beams, blower on high, A/C clutch, etc)

If your alternator is good and the battery is charging, follow the steps to diagnose a parasitic drain.

As stated, disconnect the negative lead from the battery, then hook an ammeter up between the negative post on the battery and the negative lead you just disconnected.

You want AT MOST 50 milliamps of draw with all accessories off.

Now go around pulling fuses once at a time till you find the circuit that is causing the drain. Then you should be able to use a schematic to find out what is run off that circuit and narrow it down from there.

PROTIP: Put a 5 amp fuse in line with the test leads on the meter. The internal fuses in multimeters are typically expensive and somewhat tough to come by compared to automotive blade fuses. Fluke is really proud of their fuses.

PROTIP: The above procedures won't work on modern GM vehicles that use a CAN or similar. They can stay awake for approx 45 minutes and have a pretty big draw during that time that can lead to false positives. You need a Tech II to put the vehicle to sleep before you can start diagnosis.

PROTIP: If you find that you do not have a huge battery draw (50-70 milliamps) and your battery is charging well and you do not have a 150 amp meter to check between the battery and the alternator, check all the connections. Make sure they are all clean, tight, and secure. Measure the resistance of all the battery cables and replace the ones that have any significant resistance (more than an ohm or 2). You should disconnect the battery cables from the load before testing resistance on them.

PROTIP: If you use an autoranging multimeter, make sure you note the range when taking your readings. I can't tell you the amount of times something has been misdiagnosed because of an autoranging multimeter being smarter than the tech doing the work.

PROTIP: A poor man's test for bad connections is to take a pair of jumper cables and go from the negative on the battery to a good engine connection and see if your situation improves. You can do the same from the positive on the battery to your power distribution area, thich is a major pain on an older GM because its on the starter.

I had a similar situation with one of my eclipses that was drawing 0.12 amps with the key off. A bad factory amp was the culprit. I swapped it out and my battery life greatly improved.

93gsxturbo wrote: . PROTIP: The above procedures won't work on modern GM vehicles that use a CAN or similar. They can stay awake for approx 45 minutes and have a pretty big draw during that time that can lead to false positives. You need a Tech II to put the vehicle to sleep before you can start diagnosis.

Ain't just GM. Everybody does it now. The longest I encounter on a regular basis for sleepytime is Fords. 40 minutes is about normal...for no good reason I can think of.

All the rest of your tips are groovy too, although I lean towards 40ma.

In reply to Streetwiseguy:

And while you're waiting for it to go to sleep, some jerk goes and opens a door and you have to start all over again. If you're lucky, he doesn't blow the $16 fuse in your Fluke. That's YOUR job, when you go to measure voltage and forget to switch the leads on the meter.

At least Ford's been going to the style of door switches that are incorporated into the latch, so you can open the door and trip the latch. Car thinks door is shut, and you can access the inside just fine. (Just remember to NOT slam the door until you unlatch it!)

Another good idea is to connect the ammeter first and disconnect the battery in a way that keeps everything energized without actually breaking the connection, as opposed to disconnecting the battery and then hooking up the meter. It definateIy helps with the new cars that power down after a while.

I also had a guy accidentally build a latching relay, and when the battery was disconnected to do the test, it would break the latch, and the problem would go away.

later, matt

Tapping the starter to get it to work may be the place to look. Click, click= solenoid is working. Hitting starter with tire iron= dislodge stuck brush or made poor connection. Was the battery actually dead or low ?

Very low. I got home but hasn't moved since, I don't trust it.

New starter is in. I pulled all the fuses and checked across the fuse contact points with a Meter. The only one showing a draw is the AC/heater fuse.

Further investigation today ....

Dan