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Discussion Starter #1
hi everyone. I have 1991 plymouth acclaim Le with a 3.0 v6. Today my check engine light came on while driving to work. When I got to the parking lot I recieved the following codes
12
17
41
55

I know the code 17 seems to happen when it is very cold out. I have already fixed the thermostat and now I get great heat.

The 41 has me baffled as it seems to charge the battery fine. My volts gauge is always smack in the middle of the normal range (I have digital gauges so it stays on the middle "bar") and my battery is less then 6 months old. I know it was cold out but would this have an effect on the charging system

If I choose to change out the alternator, would it be possible to go ahead and install the 120 amp rather then the 90 amp? Or should I try and see if I can rebuild this 90amp?

The car has less then 45K on it
 

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Before changing the alternator check for any corrosion. I've had the code come up with simply corroded cable connections.
I've swapped from the 90 to 120 amp the only time I ever had to replace an alternator on a FWD car.
 

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Check the battery voltage with engine off and at idle with a multimeter. Do not go by a 'bar gauge'.
 

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I would disconnect the battery and go over all the connections at the alternator, the grounds (there are several) and at the PCM. I would get the alternator tested before you replace it. I went thru the error 41 issue this past summer. My alternator was bad, my electrical connections were corroded. After repairing all that I still had an error 41. I also had to replace the PCM to get it all working again with no codes. The error 12 could be from disconnecting the battery, B+ connecttion for the PCM or battery voltage dipping below a certain level while you are cranking or a low battery.
 

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Code 12 is usually set whenever any new code is set. Unless an issue is suspected from some other symptoms, simply ignore code 12.
 

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Clear the code. Do a load test on the alternator to see if it keeps charging as load is added. Sometimes they fall flat (i.e. stop charging) when a heavy load is added. That could be an indication that the brushes are worn to the limit.
With a voltmeter, you can usually load test the alternator yourself by placing the voltmeter across the battery and adding load to the system by turning on items like headlights, rear defrost, cigar lighter, blower (full blast), and wipers. If the battery voltage drops to 12 to 12.5 volts as you add load, rev the engine. If there is no change in the voltage, the alternator is not charging. Typically, with a good battery and alternator charging, you will see voltages of 13 to 14.5 VDC (depending on battery charged state).

AutoZone will also perform a free charging system test.
 

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Discussion Starter #7
I am going to clear the code tonight. I know I had the defroster (both rear and front on) my lights and the radio was going too. I have a battery charger that displays the alternator percentage as well as battery voltage so I will hook that up tonight and see what it does. The battery cables were replaced when I got the car. I am not sure about the grounds though. I will look into that

I have the alternator with the fan on it. does anyone know which model that is? Does it make sense to order the brushes or is it better just to replace?
 

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I am going to clear the code tonight. I know I had the defroster (both rear and front on) my lights and the radio was going too. I have a battery charger that displays the alternator percentage as well as battery voltage so I will hook that up tonight and see what it does. The battery cables were replaced when I got the car. I am not sure about the grounds though. I will look into that

I have the alternator with the fan on it. does anyone know which model that is? Does it make sense to order the brushes or is it better just to replace?

Most people just replace the alternator these days. If you are good at disassembling and repairing sub-components, go for it. You will have trouble finding the brushes unless you have a well stocked alternator/starter repair shop in your area. You can often find alternator brushes on E-Bay.

Also, replacing the brushes one time might be acceptable, but you will eventually get to the point where the bearings inside the alternator case wear out. I am at 234,000 miles on my original alternator (on the 96 mini) with 1 set of brush replacements, but the bearings are getting noisy. That may be a topic for another discussion... :).

If you determine that your alternator needs replacing, try to match the style to the existing one you have on the car. It will either be a Bosch or a Nippondenso. They are suppose to interchange perfectly, but I have had problems with the thickness of the spacer causing slight misalignment and causing a belt squeal when I went from one style to another. It could be that I just got a shoddy rebuilt unit with a poorly machined case or one that was dropped and caused some case distortion. I just thought I'd mention it if you have a choice to stay with the same brand.
 

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If you do not have a good digital volt meter, I would go to Autozone, advance or anyone that would do a battery/charging system analysis. A charger is not a good measuring tool. You have no idea if the brushes, diodes, field coil or even the regulator is faulty. I sure wouldn't go tearing apart an alternator until you know what is bad.
 

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Discussion Starter #10
john. This car is no where near 50K that is why I am surprised that this is even happening .. but then again .. age can kill anything . I am going to look at getting a 120 amp if I have to replace it.

Rickorino I do have a good digital volt meter. I just saw that it had an alternator read out on the charger
 

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john. This car is no where near 50K that is why I am surprised that this is even happening .. but then again .. age can kill anything . I am going to look at getting a 120 amp if I have to replace it.

Rickorino I do have a good digital volt meter. I just saw that it had an alternator read out on the charger

Only 50K on a 91? Have you been able to positively verify that? I would never expect an alternator to have a problem at that low mileage unless it is an infant mortality failure :). Are there any signs of rodent damage to the wiring? Also, I just went back to post 1 and see that you have a 3.0 while I was visualizing the 4 cylinder. I'm not sure they had both a Bosch and Nippondenso available for that model. My bad for not reading closely.

I suppose if the engine had been run for a minute or two with no belt on, you could get an alternator error code. I would clear the codes and start from scratch with the charging test. Also in the past on EEK cars, I have observed a weak battery causing a lot of false codes that were meaningless and never came back once a fully charged battery with cleaned cable connections was installed.
 

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I had a low mileage alternator fail on my 1992 New Yorker around the 40k mile mark. The car was probably 10-12 years old at the time but the failure was a noisy bearing not a failure to charge.
 

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Discussion Starter #13
John.. I am not kidding. The car is verified though car fax. roughly 44k. it was literally driven 2k per year. I got the car for 600 cash off a dealer lot!

That is why I was surprised today since the Check engine light came on when I was driving it to work. The car lost no power, and the volt gauge stayed constant.

I looked briefly at the wiring today on my lunch and did not see any rodent damage. I had a rodent eat through part of the harness on my mercury and that was not fun.

I think fist I am going to clear the codes, clean the battery terminals and see what happens.

On a side note this thing can haul [I should have my mouth washed out with soap for using such terms] even with the a604. I love these cars simply because they are built like tanks
 

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Discussion Starter #14
I forgot to also ask. If it turns out to be the alternator .. which one is better? the bosh or the nipennso?
 

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Discussion Starter #15
ok.. this is kind of wierd. I drove the car home today and in the middle of my drive the check engine light comes back on and the volt gauge goes low. It was as if the alternator stopped producing power. GEt close to my house and went over a pot hole hard.. (did not see it) and the gauge goes right back to "normal" ( my lights got significantly brighter)

I cleared the codes and almost immediately the check engine light came back with the code 41

could this be the brushes going bad?

I was also getting 14.5 volts at the battery when it was working. The wires look fine. I also cleaned the terminals
 

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Start checking the connections. There are many involved with the charging system. I remember six to eight ground and three to four B+connections for charging just under the hood. Don't go by visual appearance. Take them apart and clean them up. I doubt the brushes are worn out with the low vehicle mileage you describe. You may have to go point to point with your volt meter checking for voltage drops while wiggling.
 

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Discussion Starter #17
I am going to go ahead and take the alternator out and have it tested. Meanwhile I am going to clean the grounds as stated and all connections. Hopefully that will fix it. If not then I guess I need to get a new one
 

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It's also possible that you have an intermittent short circuit somewhere in the car.

Several years ago, I was getting an intermittent skipping/brief cutout at highway speeds, which was a stumble and stall at lower speeds. It took me 2 months to observe that every time this happened, my voltmeter snapped down to about 10 volts, then about 1-2 seconds later snapped back to normal. I was getting a code 13, not because the MAP was bad, but because I lost vacuum as it almost stalled.

It took me another month to find that my fan motor had partially shorted windings, and was drawing 13 amps when running, and 36 amps instantaneously at turn-on. Replacing the fan motor brought it down to 4 amps, and a 13-amp spike at turn-on.

But the problem remained. I finally decided it was an intermittent short in the fan motor wiring, and I never was able to pinpoint it. So I wired a new harness to bypass the factory wiring, and that solved it for good.

But because it slammed the voltage down to 10 volts, it would have been easy to mistake it for a charging system problem. So if your alternator tests good, you should start looking for short circuits.
 

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Discussion Starter #19
Yeah I have to really go through the entire charging system cleaning up grounds and making sure everything is up to snuff. I was tinkering with it a bit last night ( Driving my new car in the winter ) and I noticed that it was not charging at all again. well I guess if this alternator checks out ok .. then the wiring will have to wait till it gets warmer here in new york..
 

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Discussion Starter #20
Ok over the weekend I was running some tests on the alternator. I ran the car for aproximately 5 min and everything was fine. I had tested everything according to the service manual and the alternator was running fine during this time. All of a sudden on the last test with a volt meter, the voltage went down to 12.5 v from 14.5. Immediately the check engine light came on and the 41 was set. I turned off the car. Waited till it cooled down.

Started the car two hours after with the volt meter hooked up again at the battery. 14.5 volts! What could this be? It seems that once it warms up the volts go flat
 
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