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#1
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Alternator not working - shouldn't battery light come on?
Yesterday I got out of work and discovered my battery wouldn't turn my starter.
Got a jump from someone and then drove home, lights were totally dim by the time I got back. The battery light never came on on the dash though. It has in the past when I had intermittent alt problems from a loose belt. Also, yesterday before all this I found that my radiator cap had failed and was leaking coolant under the hood. Is there a good chance that the coolant could have fried my alternator? It was just replaced this past summer, so seems a bit odd to happen now, also seems like too much of a coincidence that both things would happen at once.
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#2
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There is a certain "low" threshold before the alt light comes on. It can also be burned out.
Check your voltage regulator and make sure all connections are clean. A coolant leak can cause problems for the alternator, if it gets totally soaked and saturated with water and coolant. How old is the battery? Also, was the battery electrolyte level properly maintained? Low levels will kill a battery.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#3
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Quote:
The battery charges with a charger. Is the voltage regulator the most likely thing in an alternator to get "fried" by a short? I've replaced that before, it is a 5 minute job.
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#4
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That, or the windings. Usually the voltage regulator is the first to go.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#5
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Charge up your Battery and turn the Key to the position where all of the Warning Lights light up. If the No Charging Light does not Light up it could be the Bulb is burned out or there is an issue with the ground in the Instrument Cluster.
If the Bulb is burned out your Alternator will not charge because the Bulb is part of the circuit that causes the initial excitation to start charging. A few Members have said that when one of the Brushes on the Voltage Regulator was worn too short their No Charging Light never came on and they did not know the Battery was discharging.
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84 300D, 82 Volvo 244Gl Diesel |
#6
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Thanks, I will check to see if the bulb comes on when I glow it.
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#7
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Why not run down to your nearest Autozone, Pep Boys, etc and have them test it for free?
John
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Certified Registered Nurse Anesthetist (CRNA) 2002 F250 powerstroke with Plantdrive WVO conversion 1983 300SD 190K miles ,sold 2006 E320 CDI |
#8
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Test the alternator or the battery?
I know the battery is fine, it charges with a charger and holds a charge, and I know that the alternator is not charging the battery, so it is unlikely that there is a charge from it on the battery terminals. Don't they need to take the alternator out to test it on it's own?
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#9
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I had exact same symptoms last summer and a new regulator fixed it.
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85 300 SD ~ 115K 82 500 SEC Euro ??K 78 450SL 164K |
#10
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Quote:
Start simple. Although removing the alternator is not difficult, it is more time consuming then checking a bulb and putting a voltmeter on the battery while running. 1- So check the bulb on the cluster first. 2- If it is not burnt out, then start it and put a voltmeter on the battery terminals. It should read at least in the 13 volt range. If it is 12 something or less then the charging system is not functioning. It could be due to a loose belt, worn brushes on the voltage regulator, bad diodes in the alternator, or the wiring/connections.
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2009 ML320 Bluetec 1985 300CD 1981 300TD Past Mercedes 1979 300TD 1982 300TD 2000 E320 4Matic Wagon 1998 E430 1984 300SD 1980 300SD |
#11
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Quote:
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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! |
#12
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Anyone know if you have to pull out the whole instrument cluster to get at that light? I have been back there before I think, but now I can't remember the whole deal.
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#13
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this is still the most bizarre thing about these cars to me. i really mean it. for all the over-engineered simplicity.. this just kills me
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1981 NA 300D 310k miles |
#14
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Yes, you do have to pull the cluster to get at the bulb (not that big a deal in W123). However, the real issue which I don't think that you've answered is, does the light come on when you rotate the key to the first position before engaging the starter? That's when all of your warning lights are tested.
Kurt
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- '79 240D - engine swap complete! Engine broken in! 28-31 mpg! Lovin' the ride! - '86 190D (W201-126) - 2.5 NA engine, 5 speed, cloth interior, manual climate controls, 33-34 mpg (sold to forum member). |
#15
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check to make sure the glow plug relay isnt stuck on.
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1981 300SD 512k OM603 |
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