Alternator going bad?

[MazdaTom]

My radar detector display voltage and even after my new battery, I'm still seeing a wide variety of voltages displayed while driving. Anywhere from 12.7 to 14.2.

Anyone know how to spot an alternator on its death bed?

If I were to go through the trouble of removing it and having it tested, does the test do anything other than measure voltage? Are they testing current too?

I'm thinking that my bad battery may have over worked my alternator and now it's on its way out.

The alternator has 61000 miles on it (I believe it's the factory unit). I also have a UR underdrive pulley but I've seen volts as high as 14.4 in the past and it didn't seem to fluctuate as much as it does now.

[Red5_02]

Typically alternator's won't stay at one voltage. If it dips under 12, then you have problems.

[kansei]

Mine has been in the 11v range for.. years now. I ran with an underdrive pulley for about 60k of the 102k miles on the car, I took it off when I turbocharged the car (didn't need the power boost anymore). I know the prevailing information out at the time said they were not detrimental to the health of the various accessories, but maybe that wasn't true after all.

I can check and give more precise numbers tomorrow --I can get readouts on my radar detector and my head unit.

[jeg0024]

I had a problem with the power cable on the altinator going to the battery being loose. My battery light was flashing on and off and the volts would jump around. Reach down there with a screw driver and flip open the cover on the cable end and make sure the nut is tight.

[D323]

if tested it measures 2 things.

voltage/amperage output and to see if the diodes are still good. If the diodes go bad, it will start dumping AC in with the DC.

You need a shop to do an ARBST test. Its a machine that is hooked up to the battery and can test the alternator output, battery condition, and wether or not the diodes are good.

Good luck.

[MazdaTom]

So do I need to remove the alternator from the car? Doesn't sound like it.

[mzdalvr]

then bench test where they hook the altenator to a battery would need it out of the car to do this. output from the altenator is normal between 12.6 - 14.4/14.6 with brief spikes above are not uncommon (also depends on accessories). anywhere at 16V steady is a sign that the alt is over-working itself and would need to be replaced. problems with your battery are a big cause for alt failure. i would check your battery (voltage drop test). if you have a voltmeter connect red to positive and black to negative while the car isn't running (if you need specific instructions on how to do this just holla otherwise you could get this checked at a shop) the voltage from the battery should be 12.6V or in that range +/- 0.2-0.4 if the battery shows 12V or lower it should be replaced.

[BRIAN MP5T]

I would not trus a radar detector to be accurate.

[D323]

For an ARBST test, nothing needs to be removed. They simply hook the machine up to your car and take a reading. Easier than bench testing.

14.4 is ideal, but if you are not killing batteries or anything I wouldn't worry about it.

Test for peace of mind if you feel the need.

[mzdalvr]

For an ARBST test, nothing needs to be removed. They simply hook the machine up to your car and take a reading. Easier than bench testing.

14.4 is ideal, but if you are not killing batteries or anything I wouldn't worry about it.

Test for peace of mind if you feel the need.

basically a battery/charging system analyzer. ya that would do it too. just for clarification 14.4 wouldn't be what you would want to see constantly - the altenator will fluctuate between 12V-15V which is a safe range.

[i12drivemyMP5]

FYI, when I replaced my alternator there was a big red warning sticker on the new one saying it could NOT be tested off of the vehicle. Coulda been a lie I suppose, I'm sure someone will think it's bullshit. Argue amongst yourselves, it's just what was there when I opened the box. Somebody go spend 200.00 to test it off the car & find out if it's bullshit or not & report back.

[BRIAN MP5T]

True.. It Can NOT be tested off because the ECU has the voltage Reg in it..

[kansei]

I never did report back with my numbers.

Mazdatom, is your radar detector a beltronics by any chance? Mine is and displays weird numbers (usually pretty low) but I put on the voltmeter on my pioneer premier and it shows normal numbers.

It may be worth getting a second opinion from a multimeter :)

[MazdaTom]

My detector is an Escort. I'll double check with my multimeter one of these days- although lately it has been displaying more "normal" readings. I've been seeing alot of 14+ volts with fewer sub 14 volts.

[kansei]

weird.. and you didn't make any changes since the start of this thread?

[MazdaTom]

Nope.

The voltage will still drop into the 12's, but only after I first turn on a new electrical system- lights, cooling fan..... It just seems to be staying in the higher volt range lately like it did long before I started having battery problems.

Weird. I hate electrical stuff.