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  #1  
Old 01-05-2019, 08:07 PM
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alternator question

My 3.0 x5 shows 119 on code 9 which indicates my new battery only has 11.9 volts. I put it on the charger to see if it shows anything different. Just hooked it up and shows 119 still. Should I charge it overnight and test it again? The production date is 3/2000 and has one button to reset the mileage and no second button. I'm trying to determine if the alternator is gone. I can go to Autozone once the battery is charged and have them test it or I can try out my new Schwaben/Foxwell scanner if I can figure out the instructions. Any insights on verifying alternator output?
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Old 01-05-2019, 08:43 PM
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Using the hiden menu or scanner is not the greatest way to diagnose alternator or battery issues. What is voltage when engine is running? What problems are you having?
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Old 01-05-2019, 09:54 PM
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After driving 50 miles on the freeway and stopping for about an hour I restarted the x5 to head home and no defroster fan. This has happened intermittently for a while. It could be a big problem shortly if we have a deep freeze. I'm checking on the alternator output after replacing the battery that only produced 300 CCA and was rated at 900. The fan replacement is pretty involved compared to the e30 and e34 projects I've done in the past.
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Old 01-05-2019, 09:58 PM
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Foxwell will make a graph of voltage. You can catch dips after the fact


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Old 01-05-2019, 10:10 PM
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I need to figure out how to get that from my scanner.
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Old 01-05-2019, 10:15 PM
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alternator question

There are a bunch of modules that have voltage.

[IMG]https://uploads.tapatalk-cdn.com/20190106/3a184d95f1facb2b3d910713d966e0e2.jpg[/IMG





The last pic most interesting: the two dips to 13.0 happened exactly when I switched from throttle on to coasting. First when stopping to turn out of a parking lot, second to park at a curb

Notice that in normal driving the voltage stays within 0.2 v min to max. The voktage regulator changes the field voltage of the alternator to change the output voltage of the alternator, this way it can make maintain steady output voltage no matter what the rpm.

The alternator makes 3 phase AC at I'm guessing 100-400 Hz never measured but I think I've heard it. That voltage is converted to DC by a 3 phase bridge rectifier built into the voltage regulator.

The voltage regulator increases the voltage hence current to the armature of the alternator any time the output voltage is lower than desired output.

The only reason for the dips is some built in lag to smooth out the controller so Its not wandering around all the time.

When you drop throttle and it normally drops to 13, when the slip rings are worn the field current will get weaker than needed to maintain output and you will get a drop low enough to trip codes.
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Last edited by andrewwynn; 01-05-2019 at 10:35 PM.
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Old 01-06-2019, 08:50 AM
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What scanner did you use to get the graphs? Mine is a 14020SCH small hand held unit. Their instructions are not the best and I haven't found the location on the menu to test the battery voltage. I just got it so I'm not that familiar with it's functions.
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Old 01-06-2019, 02:09 PM
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Quote:
Originally Posted by ahlem View Post
My 3.0 x5 shows 119 on code 9 which indicates my new battery only has 11.9 volts. I put it on the charger to see if it shows anything different. Just hooked it up and shows 119 still. Should I charge it overnight and test it again? The production date is 3/2000 and has one button to reset the mileage and no second button. I'm trying to determine if the alternator is gone. I can go to Autozone once the battery is charged and have them test it or I can try out my new Schwaben/Foxwell scanner if I can figure out the instructions. Any insights on verifying alternator output?
Yes, charge it and see if it takes a charge. It should be 12.4 or better. It is an old battery. 18 years is long past its expected service life. I would put in a new battery just because of the age. You could also have an alternator problem. Easiest way to tell is to fire it up and use a multi-meter to check the voltage at the jumper points under the hood. You should be seeing at 13.5 at idle.
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Old 01-06-2019, 02:23 PM
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The battery is a week old. I charged it last night and the heater fan worked on the way to church this morning. I will test with my meter to see what the alternator is putting out.
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Old 01-06-2019, 02:33 PM
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Quote:
Originally Posted by ahlem View Post
The battery is a week old. I charged it last night and the heater fan worked on the way to church this morning. I will test with my meter to see what the alternator is putting out.
Sorry, misunderstood. Thought you meant battery production date.
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