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#1
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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 |
#2
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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!
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#3
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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. |
#4
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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.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#5
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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!
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'84 300SD sold 124.128 Last edited by compress ignite; 03-15-2010 at 01:55 AM. |
#6
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Quote:
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. |
#7
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Quote:
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
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#8
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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.
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96 E300d |
#9
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Make sure your glow plug relay is not stuck closed. This condition can drain your battery very quickly.
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Joe ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1980 300SD - 495k miles - 'The Ambassador' ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Former Family Members 95 C280 73 280SEL 90 300D 87 300SDL (X2) 86 560SEL 84 300D 80 300SD |
#10
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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.
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed. W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html 1 X 2006 CDI 1 x 87 300SDL 1 x 87 300D 1 x 87 300TDT wagon 1 x 83 300D 1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry. |
#11
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Quote:
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.
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#12
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Quote:
Also, I did not realize you cannot touch the multimeter to the two terminals 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! |
#13
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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.
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#14
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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
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'84 300SD sold 124.128 Last edited by compress ignite; 03-16-2010 at 05:36 AM. |
#15
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[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.
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96 E300d |
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