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Alternator failure diagnoses confirmation on 82 240d.
First two paragraphs are just backstory, diagnoses starts on third paragraph.
Just got back from an 1,800 mile trip. About halfway through the trip, after a refuel of the biological units, the engine wouldn't turn over, just clicking. The car took to a jump ok and we found what was likely the only available correct battery in International Falls, MN on a Sunday morning. Slapped it in and went on our way. About 650 miles later after we crossed the Missouri border and the sun had set, with the A/C blasting, two cell phones charging, Garmin guiding, radio cranking, headlights burning and wipers slapping time with a sudden cloudburst, we lost the headlights. They're LED and without the correct voltage they just shut off entirely, no warning. So with a quick bit of thinking I shut down everything electrical we didn't need and the headlights lit back up. It was obvious at that point that the alternator either wasn't charging, or at least wasn't keeping up with the electrical demands we were putting on it. I pulled off the highway, with three hours of driving left to go I stripped the car down of any electrical loads we didn't need to keep moving, aux fan disconnected, radio off, no A/C, marker light bulbs removed, one tail-light bulb removed, license plate bulbs, you name it, if we didn't need it to move forward, it was off or removed. Thankfully the rain subsided so the wipers were not necessary any longer. The car limped the rest of the way home, rolling in to it's home berth at roughly midnight with the headlights flickering. The next morning it was dead, the clock had stopped at 9:30am. I put it on the battery charger, 6amp charge, and went about reading up on charging problems here. After my Peachparts Mercedes charging system 101 education I went about checking common issues/symptoms, here's what I found:
So I'm pretty sure I need to replace/rebuild the alt regardless. The noises it's making are bad wrong like a bearing is shot. But what I don't get is how a shot bearing is preventing good charging. Perhaps is has that bearing problem plus another? I also still don't get why the batt and brake wear warning lights aren't illuminating at key-on, and why they never illuminated when the battery was nearly depleted and the alternator not charging/keeping up with electrical demand. Those conditions make me think perhaps the charging incident is caused by a problem elsewhere somehow. Any thoughts? |
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Make sure your glow plug relay isnt staying on. I went thru battery and alt only to find my relay wasnt releasing.
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I never thought to check that when I charged the Battery. I am curious what an Auto Parts Store has to say when You take the Alternator for the Free Test. If the Rotor (it has the Field) is hitting the outside Steel Parts (Stator Core) of the Alternator due to a bad Bearing it would be grounded when it is not supposed to be. I suppose it is also possible for something to happen to the Slip Ring Connections if the Bearing on that end is shot. |
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Have you checked for AC voltage across the battery terminals with the engine running? Set meter for AC voltage range higher than 60VAC to get a good reading - if necessary, work your way down in voltage scale switch. |
You must find out why your battery light isn't illuminating. Have you pulled all the fuses and checked them all? If the battery light does not come on, the alternator will not charge the battery. Pull the cluster and check the filaments of the bulbs. Clean all the ground contacts too.
Its a little confusing, because you say when the car is idling the volts on the battery is 12.7v....that means its charging, but if the battery light does not illuminate....how's that possible? Has someone been messing with your electrical system? What about these led lights? Is the stereo aftermarket? With subs and an amp? I am wondering if your just over running your charging system. These cars aren't generators.....typically if you plan to use all your house hold gadgets and every accessories in the car....you really need to upgrade the charging system, thicker wires...beefer alternator....dual pulley alternator....maybe even a solar panel... |
To give closure, alternator replacement appears to have cured my issues. Battery and brake warning lights now illuminate at key on and shut off after engine start. Reading 14.4vdc @ idle after the GP relays click off.
Curiously, after charging the battery and parking the car for a couple of days while I awaited a new alt, the battery discharged again. Now I had the old bad alt hooked up still so perhaps it had some internal fault (short) that drained the battery. Well, that's what I'm gonna tell myself for now. With everything all repaired now and the key off and battery discon I see no voltage drop upon connecting the battery, so I don't think I have a parasitic draw anywhere. About the LED headlights, they're plug and play 7-inch round units manufactured by Truck-Lite. They're very low draw, probably less than the brake lights, however they're not tolerant of voltage drops, so the internal circuitry will cut them out once levels drop below tolerance. The rest of the car is stock, except LED dome lights and license plate lights. I'd do the marker lights but the LED units I've found don't seem to play well in the housings, resulting in poor illumination/visibility. Same with the brake and tail lights. The signal lights are similarly a no-no and have the added problem of screwing up signal operation, as the draw isn't enough to operate the flasher units. To correct this one must wire a resistor in line, which defeats one of the major advantages of LED, which is low power draw. The radio is all stock. |
I've heard that if the rectifiers, one or more, are shot then leakage back thru the alternator could occur. That was one of the reasons I wanted you to check for an AC voltage reading at the battery; the other is the battery charges poorly or not at all with rectifier failures in the alternator. Generally, a rectifier failure requires replacement of the alternator anyway.
Glad to hear you are up and running! |
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Good job! And happy motoring.:D |
Well, the no-charging problem came back. I got one fifty mile drive and that was it. Went to start it and no battery warning light, no brake warning light again. Really frustrated, going to go back through the testing again, but I may be pulling this brand new alternator.
Not sure what else to do. Really frustrated now. |
No battery warning light and no brake warning light sounds like a possible problem with the electrical section of the ignition switch.
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I am wondering if you have a ground issue? Have you removed the ground cable from the battery to the chassis and cleaned the contact? How does your positive battery cable look? They tend to swell with corrosion over time, its also possible to have broken strands of copper near the battery clamp. Did you take the battery in for a charge and testing after you replaced the alternator? I drove my 300d for over a month with the alternator not charging the battery....it seems strange that you can't go a mile before its dead...its also possible the starter could be causing the drain...
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DIAGNOSTIC VIDEO, PLEASE WATCH VVVVVVVVVVVVVVVVVVVVVVVVVVVVVV Damn car won't charge - YouTube ^^^^^^^^^^^^^^^^^^^^^^^^^ DIAGNOSTIC VIDEO, PLEASE WATCH I can get the lights in the dash to illuminate if I provide ground to the blue wire at the alt. |
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http://www.peachparts.com/shopforum/diesel-discussion/341558-83-300sd-electrical-issue.html
I'm going through similar issues... |
That electrical plug for the alternator is pretty dirty. I would pop it open, make a note of the orientation of the wires, clean them really well with electrical cleaner...make sure they are nice and shiny, re tension the wire connectors and confirm all the solder joints are good. Its possible the plug is staying taught in the alternator, but the individual plugs aren't making contact.
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It's cleanin' time! It's also been pointed out to me that the voltage regulator can be damaged by connecting and disconnecting the circuit while the engine is running. YMMV |
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I am running out of ideas. The only other thing I would suggest, is to pull the fuse box cover and check all the fuses...remove each fuse and inspect the ends...Reading a lot of threads on the matter, they say it is possible to have a fuse melt inside. I would also pull the cluster and clean the bundle of grounds behind it, and do a visual inspection of the cluster. All the gauges connect together and that is how they are grounded, by touching one another.....I would also clean and check the wires on the starter...I suppose its possible to have a bad solenoid and that cause your issues, my starter went bad and killed my battery.
To see if you have a bad ground connection on the block/alternator. You can take the negative side of a jumper cable, clip it on the negative side of the battery then the other end to the engine block or alternator. I read a thread where the glow plug relay can also be blamed, you can pop it open.....remove the connectors then see if your battery light comes back on. |
I would think the fact that the Battery Light and Brake Light not working at the same time would have some meaning - like the driver's side front window and passenger side rear window circuit diagnostic.
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My new good alt wouldnt charge so I ran a 10 gauge wire from the alt housing to where the neg battery cable bolts to the chassis. Alt gives 13.3 amps now. A simple fix to try
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take the new battery back to the store and have it tested. replace if it's partially low on CCA. it's also possible that whatever killed your first alternator is still causing problems. |
When you turn the key on, the diodes within the alternator provides the path to ground to turn the charge light on . You said you were able to turn the light on by grounding the blue wire after removing the connector.
Possible causes: 1. Alternator diodes blown open circuit (all 9 of them). 2. Connector not making good contact. 3. Alternator not grounded well. 4. Cluster traces damaged. This can happen if the ground strap on the bell housing is not making good contact while you start the engine. |
"Alternator makes a rhythmic rattly banging noise during operation (only with wires connected)"
This is a weird one and raises a red flag. Did this happen with the new alternator? Did you find the cause? |
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Use a digital ohm meter and set it on k ohms scale. Put it on the D+ terminal (the blue wire terminal of the alt) and ground (alt case). You should get a reading of around a thousand ohms. If you don't get a reading reverse polarity of the leads. If you still don't get a reading, the diodes are blown open. |
I used the block terminal and get a 14.3 ohm reading.
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Thank you, I'm going to test ohm load between alt housing and battery negative terminal. That should prove out if the alt is grounded well or not. I know the connector is making good contact, as I've separated it and manually connected each lead. The cluster traces you speak of are the traces in the dashboard instrument cluster, yes? When I had the cluster out I noticed my oil pressure gauge is weeping slightly. Do you know if engine oil is electrically conductive? This could be a problem. Quote:
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Okay, I'll crawl under the car again.
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Here's an important diagram I'd figure I'd post up. It's what I've been using to test and diagnose with.
http://i.imgur.com/4cDYnb6.png |
Said diagram is just a ? inside a blue box here.
Diagram showed up, thanks. |
An ohm meter to check the grounds may not always tell the truth. An ohm meter puts micro amps into the circuit under test. An alternator 50 to 100 amps. A starter motor 300 to 350 amps. The effort is better spent cleaning all grounds and electrical connections. Try a jumper cable from alt case to battery - terminal.
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Now it fluctuates between 9.5 & 9.8 ohm.
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Ok, I've tried grounding the alt housing to the battery neg terminal, and running an alternative source of 12vdc to the exciter terminal and still nothing. This alt is going back.
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Did you try tightening the belt?
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Well at least you learned a few things :D |
Ok, alternator #3 is in place. It's giving 13.8vdc after the GP relays click off. Alt #2 was giving 14.4 until it just quit. Not sure what to make of that.
I had AutoZone test alt #3 before I put it on the car and it tested good, three times in a row in fact. So that's great. Then I put it in and got 13.8. Seems ok but a bit lower than last time, so I drove the car up to AutoZone and had them run their on-car alt test. Came back with failed voltage regulator. Alt still giving 13.8. I'm guessing their machine is wrong. Thing about their test is that they start with the car off, hook to the battery, push a bunch of buttons then have you start it. Now I have my aux fan set to run whenever the key is turned, plus the GP relay does it's thing and continues to run the glowplugs for a while after start, so voltage after a start is gonna read low for a bit. I'm guessing that's why it said failed voltage regulator, but I dunno. I think I'm going to have them test again with the GP relay unplugged and the aux fan unwired. As of this morning I'm still reading 13.8VDC. |
Hi Jeffroooo,
13.8v is a good enough voltage to charge a battery. It's at the lower end of the scale, but anywhere from 13.8-14.4 is correct. Lower voltages of 13-13.7 are also acceptable but not correct for a Bosch system. It's a bit of an old debate on 'what should the high voltage charge be'. Bosch have always said 14.4/5v but other car manufacturers say 13.8v because they think anything higher might fry sensitive electronics. Are these new alternators you are getting or used? There are plenty of people selling 'rebuilt' alternators around that replace the voltage regulator and that is about it. Give it a lick of fresh silver paint and that's 'fully rebuilt'. Hope you get better luck with this one. Remember if your battery is fully charged, your alternator output will drop off. Drain your battery down a bit (engine off, lights on) and then see what your alternator puts out. If you changed your battery between tests, then that will also give you a different result. A tired battery will place continuous strain on your alternator. Best to replace your battery when you feel it's on its way out. Trying to get the last out of a battery is taxing on the alternator (and electric motors). |
I have/had the same issue with my SD.
Reman unit 120 days old, no battery light, but jumping a ground the the blue lead=battery light. Not charging, killed a new battery, starter is fine. I installed a "new" Iskra, that's what the fella at Motor City Reman siad. No where on the packaging or paperwork is the word Iskra. My mechanic says it's a reman. It has a two year warranty tho. Problem solved. It's charging at 14.33 right now. |
I think I'm going to have to entertain the thought that perhaps my car is killing these alternators. Alt #3 just crapped out this morning. Got about 100miles out of it.
Maybe GP relay? I don't know. It seems like it's shutting off properly. I can put a multi-meter on the battery and see when it clicks on and off by the voltage change. Once the glow plug relay has clicked off, unplugging it does not elicit a change in reading. I've also tried pulling the fuses one by one to see if any voltage changes occur, they don't. I don't regularly run a lot of electrics either, hell it's been cool out so I haven't even been running the A/C. Since I do most my driving in the day it's been the radio and that's about it except the brake lights and blinkers. Battery tested good and comes back with 12.7vdc when fully charged. |
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