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Discussion Starter #1
DH was told yesterday by an alternator rebuilder that one of our alternators is good, after we had been told by O'Reilly and NAPA that it was bad.

He also said that if the alternator bulb in the dash is burned out, that can prevent the alternator from charging.

Has anyone ever heard that before? Is it true? Is it a big job to replace the bulb in the dash?
 

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Discussion Starter #2
ADDITIONAL QUESTION: What bulb do we need? This is the alternator or charging or battery light. I don't have the car here, so I'm not sure what its label is.
 

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I have never heard anyone ever saying that a burned out dash bulb can prevent the alternator from charging. I very much doubt it is true. When my alternator died (twice) I did a fair amount of reading on the subject, and never came across that theory.

I don't know what size bulb you need.
 

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On most cars including ours it is true. All three wires must have current at the plug for the alternator to work properly. The L or light wire gets it's power through the bulb.
Lots of buicks have this problem.
Bulb size most likely is a 194.
 

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Discussion Starter #5
DH got in behind the cluster yesterday and found that the connector for the light was not fully pushed in. When he pushed it in, I guess he had the car running, and the car died.

Also, the clip on the connector has now broken off. Got any ideas for fixing it?

The car still runs rough at low idle. I suggested checking compression again, more Seafoam, and/or checking or changing the O2 sensor. He doesn't think those are the problem. Got any other ideas?

TIA!
 

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I'd really like to know how well the seafoam did for the compression.
Future records kinda thing, to help the next person.
 

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^Yes, I'm really curious too. And if the compression is still low, on one or more cylinders, that would explain the rough idle. If the compression is now normal, then you would start looking at other causes of the rough idle.

BTW, sorry I gave the wrong answer on the "can a burned out bulb prevent alternator charging" question. That was really surprising to me.
 

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Paseo
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The way the light deal works is this, the ignition switch sends + power to one side of the bulb. This is the signal that tells the voltage regulator to turn on. The + signal is met by resistance and this lights the bulb. Once the engine spins the alternator AND the regulator is supplying the field current the resistance will be over run with a returning + signal. Now with no ground for the bulb it goes out.

If the seafoam returned compression to the 0 cylinder then another application may be the trick.

By the way, who or what is a DH? :eek:
 

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Discussion Starter #10
DH is talking about borrowing the compression-testing equipment again. Until then, I wanted to respond that the Seafoam apparently has been pretty effective at removing carbon. The oil gets really black when the car is run with Seafoam in the oil.

I'm wondering if Auto-RX would be better at removing carbon.
 
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