All,

I am curious about the behavior of my alternator.

Long story short it died Friday night, wife & son in car after a 90 mile round trip. They made it home on it's own power. Sat AM, I jumped it and got it up to the garage, voltage guage dead. Pulled it and pulled the brushes, which "cupped" for lack of a better word. Checked prices for complete alt and brushes alone and went to my local AZone to have it checked although I was sure it was dead. It put out 1.5 volts and was screeching like a banshee, bearings shot. They didn't have one in stock ($200 and 3 days), so I went to the phone book and found one for $150 (Pep Boys). All is well now.

Here's the main question, my voltage guage now is right at 12 V, before the failure it was closer to 14 V. Was this increased reading because of the bearing play? Like I said I am just curious and watching out for further problems.

Thanks, Art
87 740 Turbowagon
73 1800 ES
94 !@#$%^& Jetta

Use a digital voltmeter to verify alternator output while the alternator is in the car and under load. It should put out 13.8 to 14.4 volts. It may be fine, but you could have a problem with the internal voltage regulator. While you are at it, verify less than 0.1 volts drop from the alternator chassis to the engine block (verifying the ground connection).

I favor sticking with the exact part when possible. Importec sells your part for $182.13, shipping is free and it arrives in two days.

http://www.importeccatalog.com

Just enter the year, make, and model and go to the category "Engine Electrical" to find the alternator.

You might also do price comparison at:

http://www.thepartsbin.com price = $169.57
http://www.alloemvolvoparts.com price = $169.57

BTW, they all have free UPS ground on orders over $50, its just that only Importec (as far as I have found) gets it to your place within 2 business days for some reason.

Regards,
Rick

Thanks Peter and John,

I will try this tonite and see if I can avoid electrocuting myself. If I live, I'll give you a report tomorrow, if you care to check.

Art

Don't worry, unless you short the battery terminals, you won't zap yourself. That only really happens with mains power, although, if you, for example, put a spanner across the 2 battery terminals, it'd hurt and you'd burn the absolute F**k out of your hand.... and run the risk of the battery exploding at the same time.....covering you in acid.... it'd be a rare occasion that someone would be stupid enough to actually do this with that intention, but hey, it happens. Watch out for metal watches with cars as well...... that'd hurt too!
Az

OTOH, you may have dead/dying battery...not good to run on battery alone, deep discharge these things aren't.

Recharge the battery to full and recheck the alternator output/voltage. If it's still at 12v you prob have a bad voltage regulator and since you got a new alternator and the voltage regulator is internal to the alternator, return the alternator for another one. Have the 'new' one bench tested before you take it home.

John,

I don't know exactly what it's output truely is, I am just referring approximately on the guage with no numbers. The good thing is that if it dies it has a lifetime warranty. If I do need to get a new battery so be it, it probably it's time anyway.

Art

Do yourself a favor, and spend the $20 ~ $30 at Radio Shack for a middle of the line Volt-Ohm meter (digital or analog) and another $5 for a good book on how to use it. A good basic meter is an invaluable tool for a lot of troubleshooting. In this case it could save you a lot of time in the removal and replacement of an alternator and/or a battery that may, or may not be bad.

Peter Haakonson

Peter,

I do have a Multimeter. What do I need to touch and set my meter up for?

Thanks, Art

Set you meter for the DC scale that is closest to, but OVER 12 volts. With the car off, check the voltage on the battery. This will tell you what voltage you have without any drain or charge occurring. Take your meter off and start the car. Now check the voltage at the battery again. It should be a slightly higher value - say 14V or so. If this is not the case, there is a problem

Background:
Power is a function of Voltage (volts) and current (amps). In the real world, the 12V system in your car will vary anywhere between 11.5V ~ 14V or so. Sensitive electronics will drop the power down to a lower voltage level and provide additional circuits to filter out any unwanted power fluctuations. Your main battery is a Power reservoir that is used to start your car, and power all of the other circuits within it. Like any other reservoir, it needs to be continually refilled in order to be available when needed next time.

The job of "refilling" your battery with power is done with the device we call an Alternator. An alternator takes some of the rotational power of the engine, and converts it to electrical power. The device in your car actually generates alternating current (AC), and is converted to direct current (DC). On a graph, the AC looks like a sine wave with vehicle ground (negative terminal) being in the neutral or middle. With the miracle of semiconductors, this current is internally passed through a full wave bridge rectifier, which takes the bottom half of the wave and flips it to the top of the ground. (In the mechanical world, this is like a pump that uses valves to pump a medium on both the push and pull stroke.) The signal now looks like a continuous series of arches that go from 0V to ~16V at a relatively high current rate. This signal is put through some circuitry that will smooth it out to a good facsimile of DC voltage, and regulate it to about 14V - again, with high amperage. This is presented to the terminals of the output of the Alternator. This power is channeled back into your battery via charging circuitry.

Bottom line is this: The location where the power enters the battery is the same place that it leaves the battery, at the terminals. This is where the rubber meets the road so to speak, and where you can measure the end-game of your charging system.

Good luck.

Peter Haakonson

In addition to the other info you recieved; Do nOT uNDERESTIMATE THE POSSIBILITY THAt Pep Boys have sold you a cheap ass piece of shit alternator.
Will

OK, I'm going to break a cardinal rule and tell you how to get in trouble...

Set the multimeter up for dc voltage on a scale that covers at least 15 volts...it's probably 2-20 or some such weird range although it might be different..the idea is to avoid pinning the meter or getting a 'high' or 'low' readout on a digital. Do NOT use the ammeter or ohmeter scale.

With the engine off, put the probes from the multimeter on the plus and minus poles of the battery...the voltmeter should read above 12.8v or so on a charged battery. Start the engine...the voltmeter should read 13.2 or better but less than 14v. If it doesn't go up from the voltage you read with engine off the voltage regulator is most likely bad although it's possible the alternator has a shorted or open diode in the diode bridge (takes another tester to find the unrectified voltage).