Idiot light...charging system

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  #1  
Old 08-26-02, 07:02 PM
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Idiot light...charging system

Hey Joe...and everyone!

I have a 1985 Buick Park Avenue. 3.8L enigne. My wife was driving with a carload of kids when the car died. The battery was dead. I got it home and found a bad rectifier in the alternator. I replaced it, and the car is doing fine now...but... the idiot light for the charging system doesn't come on. I pulled the cluster and checked the bulb...it's fine. I tested for voltage at the bulb connector and there was none. It is supposed to come on during bulb test and while ignition is on, but engine off. My wife said it didn't come on while driving, or when the car started acting up just before it died. What actually turns this light on? Where should I start checking? I have never run into this before.
 
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Old 08-26-02, 07:43 PM
knuckles
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The warning lamp is powered by the "GAGES" fuse. The alternator provides the ground path until the engine starts.

Remove the connector from the alternator & ground the BROWN wire. Turn the ignition on. The warning lamp should now light. If it does, the alternator is the problem. If it doesn't, check the GAGES fuse. If the fuse is ok, check the wiring between the GAGES fuse and the Inst. Cluster. This will be a pink wire w/ a black stripe.

If the PK/BK wire is ok, check the bulb. Don't just look at it, actually check it by installing it in another socket or replacing it with a known good bulb.

If the bulb is ok, check for continuity between the bulb socket & the BROWN wire at the alternator.
 
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Old 08-26-02, 08:04 PM
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Thank you Knuckles! I'll do that! I do know the bulb is good, I tried a known-good bulb. I'll test it tonight and post the results.
 
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Old 08-26-02, 09:14 PM
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OK...there was no power at the brown wire at the alternator, and I grounded it anyway w/key on. No light. I checked fuse #16...guages...have power. I have no power at the pin in the instrument cluster connection that proivides power to the light. Does the pink/blk wire go through any other device before entering the instrument cluster from the fuse block? I followed it a short length, but it went into a huge taped up conduit of wires. I don't want to cut into this unless I have to. If there are any connectors or relays, switches, etc between the fuse and the bulb, it would make it easier for me to isolate the problem.

Another interesting thing happened. The battery died to the point that the radio wouldn't even come on in the 30 to 45 minutes that I was out there checking things. The doors were open, but they have been open for much longer w/o the battery dying. This battery is brand new. The battery I replaced it with was also new. It was replaced when the car died the first time... a few days ago. I forgot to mention that when it died on my wife, she was parked and rolled down her windows...waiting for kids to come out of school. The battery died when she rolled her windows down. She got a boost, drove 1/4 mile and the car died. That's when the battery got replaced and she drove home. After replacing the rectifier, the alt. is putting out 14 to 14.3 volts with all accessories and lights on. I am puzzled. I checked the battery connections and they are clean and tight.

It is an older car, but it is like new. I got it from an older man who hardly ever drove it, kept it in a garage, kept all reciepts and fuel mileage logs, took incredible care of it, and it only had 59k on the clock.
 
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Old 08-26-02, 09:41 PM
knuckles
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Arrow

Diagram

Courtesy of Alldata LLC. Used with permission.
 
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Old 08-27-02, 05:59 AM
Joe_F
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Cheese:

My sister had that same car. It is lackluster but gets the job done. LOL.

Did you replace everything in the alternator? A new voltage regulator, brushes, diode, rectifier and radio capacitor as well as bearings is your best bet here. Also new bearings complete the repair.

I am in the process of rebuilding a 10SI Delco and can give you the R&R instructions if you want. They are easy. Your version is not much different.

However, Knuckles gave you some good advice, go there first.

I never change one part in an alternator when I service them .
 
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Old 08-27-02, 05:22 PM
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Thank you Knuckles! I'll go over the diagram and hopefully find my problem.

Joe: I replaced the rectifier, regulator, diode trio, brushes and front bearing. I did not replace the capacitor since I have no radio interference and they seldom fail. The only lackluster quality I can find about this car is that it is prone to electrical failure. This is not the first electrical problem I've had. It seems as though ALL luxury cars are prone to electrical problems. The engine is a keeper, as i've found in past experiences. The tranny, being one of the first run units, may have trouble later on, but I don't think the early ones are that bad, just not quite as good as the later revised models.

I don't think the problem is in the alternator because it is charging. The rectifier was the bad part, but I replaced all the others since I was in there. I charged the battery fully last night, but it died again overnight. I have a short or drain somewhere. I guess I'm going to have to take an afternoon off so I can check this thing out. I'll let you know what I find!

Thanks guys!
 
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Old 08-27-02, 05:55 PM
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it is kind of weird that it would be charging with no power going to the field wire usually if you have a burnt out battery bulb or blown guages fuse the alternater will not charge due to it not getting power to excite the field, i suppose that the new regulator could be self exciting though?
 
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Old 08-28-02, 08:51 PM
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I don't know bejay. I was wondering how it could be charging with no signal. I'm just going by the voltmeter, and it read 14v running, but 0v on the field signal wire. I've pulled a lot of the dash apart, trying to trace wires without cutting up perfectly good harnesses. What a pain...I always hated those hard-to-find electrical problems. Whats more...the wire to the bulb is pink and black, but I think I counted at least 5 pink and black wires in the area, lol. The wire is brown coming out of the bulb, but that's not where the problem is. I'm not even getting power to the bulb. Such a simple system....nothing but solid wires and a printed circuit cluster. Solid wires under the dash normally don't just "go bad". Apparently one did. Hopefully I'll still have most of my hair when I find it, lol!
 
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Old 08-29-02, 09:12 PM
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Ok, common sense should have told me that this was not a self exiting regulator, since I still have to plug in the field wire. I had several problems....the alternator quit charging again....due to a blown diode trio. That was causing my battery to discharge into the alternator through the shorted diode. I went through the indicator light circuit while tightening connections...now it works. Part of my problem before was that I was working at night with a droplight, and couldn't see everything as well as needed. I also had a problem with the connection at the alternator, causing it to full-field...which surely is what blew the diodes. I went ahead and put in a new regulator at the same time (again) just to be sure.

Now if I can get the secondary A/C fan to come on when the air is turned on, I'll be OK. I'm pretty sure that is just a bad relay though.

Thank you for the diagram Knuckles! It helped.
 
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