84 300D Battery loses charge very fast
 

OK, I'm stumped. The car will not start due to no battery charge.

The alternator tested OK by our mechanic, and the battery has been tested at Sears.

I brought the car to the mechanic and they thought it was the voltage regulator, so it was replaced and appeared to be working.

Tonight my girlfriend took the car to the grocery store and the same thing happened. The car started fine at home, she drove there with lights and defrost on, parked the car and when she came out there was nothing.

Usually I am very capable of sorting out these problems, but I am now stumped. The car jump starts easily, which is why I thought it was the battery. And I am not sure if it is coincidence that it happens to be raining each time this happens.

Any ideas what this may be?

So far things that I have checked are:

Battery (Only 1 year old, and recently checked at Sears)
Alternator
Negative ground to chassis
Voltage Regulator is new

What else could it be? Relay? Car grounding itself? Bad cable? Ignition? Starter?

Thanks,
Nate

Have you put a multimeter on the terminals of the battery? Do that first. Sounds like a shorted cell to me. The alternator works, and potentially there is enough voltage for some things to happen marginally. The short doesnt dissipate all jumping current, so the car will start. However, once the car is off, the short will dissipate the stored energy in the other cells, and the car wont be able to produce starting current.

What is its voltage after sitting a while? When was it recentlhy checked at sears? what did they do? A battery on an operating alternator will show a voltage that may look OK. Ditto for a recently charged battery, a surface charge may still show an OK voltage for some time.

Next thing I'd do is remove the positive cable and put the multimeter in series with the cable terminal and the battery terminal. Get a reading for how many mA or A youre pulling. If it is over, say, 25-50 mA, then there likely is something shorted in the electrical system. If so, then you need to start using the multimeter in place of fuses to see where the draw is coming from... and track it from there.

Good luck!

Thanks JHZR2!

I was thinking that it was probably a short somewhere. When I put a voltmeter on the terminals it read about .4A. (without cables connected)

I wasn't really sure what that meant. Should there be current flowing from positive to negative with the cables disconnected? Half an amp seemed like a lot to me, but I'm not really that knowledgeable about electrical.

Tomorrow I will double check myself, and see if the current is going to the chassis.

When Sears tested the battery they just bench charged it and let it sit over night to see if it would lose it's charge.

It sure seems to me that if when completing the circuit via an ammeter, if you are seeing .4A, then you have your culprit.

Frankly, id replace battery first and foremost. Given that it has gone through a bunch of discharge cycles, IMO it is not reliable anymore, especially capacity-wise. So Id put a new one on (first testing it with your meter to see what a relevant reading should be), and see what that does. If it goes flat, then charge it with a battery charger and put in the old one until you find the solution.

Battery
 

(Long Drawn Out...Yadda,Yadda,Yadda from yours truely.)

Unfortunately, the only modern day TRUE test of a Battery is to:
1.Check the Electrolyte level,and correct.
2.Trickle Charge for up to 72 hours
(IF you even suspect the Battery may be worth saving! 'Slower is always better!)
3.Test for Voltage at Naked Terminals (After burning off Surface Charge)
(Minimum 12.75 Volts D.C.)

THEN:

4. Test for Electrolyte Density OR LOAD TEST with Resistance Loader.

The Gals and Guys @ Advance,AZ,Sears,WM,O'reilly's,Etc.,Etc. only
know what their fancy digital testers tell them...

Their tests CAN be valid but only within specific parameters:
The battery MUST be Fully Charged before testing (Among Others)

YOU AIN'T GONNA GET A FULL, SLOW CHARGE FROM ANY CHAIN OPERATION!

What am I missing here? Shouldn't connecting an ammeter directly to the + and - of a power source essentially be using the meter as a short-out between the poles (similar to laying a wrench across the battery terminals and producing a welder)? I stuck an ammeter into a household AC power strip one time just out of curiosity and ignorance. The result was that the meter tried to create a dead short between the two prongs, the resultant heat melted my positive meter lead, the power strip (one of those 6-outlet things) was fried instantly and the household breaker tripped. Isn't putting an ammeter across a dc battery causing the same effect (or at the very least, not a reliable measurement) or is this a different principle? If I'm dead wrong here then forgive me for interrupting the thread, but that seems... odd to me, unless I've missed something major. I'm not an electrical person either.

Measuring volts across a battery's + and - I understand perfectly. But I was under the impression that it was impossible to do so on an amp setting.

yeah, only do this with the key off and everything turned off on the car...
even headlights will fry your meter...
setting the meter to ma and leaving the neg cable on the battery, and hooking the meter between the battery and the positive cable will show what the clock, and anything else running is pulling. it should be around 25ma...
500ma (.5A) is a LOT

If I were you, when your finished with the car for the day, disconnect the battery until the next morning. The next day, reconnect the battery, and try and start the car. If it starts, the battery is holding its charge, if it doesn't, you know the battery is suspect. If the battery passes that test, I would recheck the alternator, by disconnecting all the wires attached to it, including the heavy battery cable, put your multi tester in continuity mode, and place one lead of the tester on the alternator battery connection post, and the other lead to the engine block or any ground point. If you get a continuity reading, it means that one or more of the alternator diodes have failed, and is allowing current to flow from your battery to the engine block. I had that happen to my car, and if the battery were left connected, it would totally discharge in a matter of a few hours with the key in the off position.

Make sure your glow plug relay is not stuck closed. This condition can drain your battery very quickly.

Make sure you have a FULLY charged and good battery and do the followings with a DMM:

1) With the car running. Check the voltage of the battery terminal. It should be normal 13-14.4V. This verifies the alternator is working.
2) With the car off and all lights, radio off. Remove key. Disconnect -ve terminal and measure any current draining the battery. It should be mininal < 500ma. The residual current is for clock or alarm etc.
3) If it draws a lot of current then go the fuse box and remove each fuse then measure the current across the fuse terminal. Most should have 0 current, except the fuse to the dash (it should be small also ).
4) If there is a massive short somewhere then there may be a burning smell.
5) If there is a short then the fuse would blow unless the fuse is over-rated.
6) I have resolved a lot of shorts in this manner.

Good luck.

You are right - battery terminal to terminal is shorted and would blow the ammeter fuse if just touched to both sides.

Ammeter needs to be inline with battery cable, and .4A shouldnt blow it.

If it were a bad diode, is this something that can be replaced? Or is a new alternator needed?

Also, I did not realize you cannot touch the multimeter to the two terminals:o Luckily I did not blow the meter. That is where I was getting the .4A. I need to do some rechecking and report back here.

I have not had a chance to work on the car today, but thank everyone for the replies. I wish Cumminsforum were this helpful for my other diesel!:thumbsup:

Also is there any way to tell if the battery is bad/shorting itself with the multimeter? I am still pretty new to using one of these.

DMM (or Analog)
 

Baer,

Youse gets one O those Manuals with your DMM?

(Direct answer to your last question: See my first reply in this post. [#5] )
"4. Test for Electrolyte Density OR LOAD TEST with Resistance Loader."
http://en.wikipedia.org/wiki/Hydrometer

If not this will get you started:
http://assets.fluke.com/appnotes/automotive/beatbook.pdf

Excellent Reference source:

http://us.fluke.com/fluke/usen/Training/Safety/default.htm

http://us.fluke.com/fluke/usen/Training/Demos/default.htm

http://support.fluke.com/find-sales/Download/Asset/2071940_A_w.pdf

[QUOTE=Baer;2426868]If it were a bad diode, is this something that can be replaced? Or is a new alternator needed?

Yes, the diodes can be replaced, but the biggest problem is being able to find them. The other thing is, there may be another problem with the alternator that may have caused the diode to fail. If you do the test, and you do find continuity between the alternator battery connection and the alternator case or other ground point, you will have your current drain isolated.