took voltmeter to batt terminals......is my alternator dying....PLS READ....

[ryan roopnarine]

i know i should have taken alternator voltage measurements, i didn't, because i couldn't drive the car that way and see the vom at the same time.......shoved VOM probes into the battery terminals, and stuck VOM under the loop in the rear armrest so that I could look back and see it.....started the car with a battery with voltage of 12.45, turned on rear defroster, wipers to fastest, a/c, radio, and high beam headlights, car goes down to about 11.75. drive around for 10 minutes, gradually decreases to 11.15. stop the car's engine, battery voltage creeps back up to 11.8 or so..am able to restart the engine....is this likely the alternator???? there are no autozones less than 6 miles from here, so i can't take it there and get them to test my car. i'd like to overnight a regulator from bma if its likely this...comments, anyone please.

[Bill R.]

this would happen just after you got it back from the mechanic... Perhaps one of the connections to the alternator was affected or the battery connection up on the firewall.. If all of that checks out good then yes I would say its likely the alternator, but don't jump to any conclusions until you check it out. Also check things like the belt tension, if its too loose it may not charge under load at higher rpms







i know i should have taken alternator voltage measurements, i didn't, because i couldn't drive the car that way and see the vom at the same time.......shoved VOM probes into the battery terminals, and stuck VOM under the loop in the rear armrest so that I could look back and see it.....started the car with a battery with voltage of 12.45, turned on rear defroster, wipers to fastest, a/c, radio, and high beam headlights, car goes down to about 11.75. drive around for 10 minutes, gradually decreases to 11.15. stop the car's engine, battery voltage creeps back up to 11.8 or so..am able to restart the engine....is this likely the alternator???? there are no autozones less than 6 miles from here, so i can't take it there and get them to test my car. i'd like to overnight a regulator from bma if its likely this...comments, anyone please.

[MikeV]

You're not charging, so it looks like the alternator. Test at idle directly to the alternator - it might be fine, it could be something as simple as a loose connection - i've had this happen. Cheaper than a new alt.

[ryan roopnarine]

at the b+ or higher of the two nuts, i'm running 11.71 after startup. UNLESS there is insulation on the bolt affecting my reading, my reading at D+ on the alternator is 8.76 volts. bill, how would i make sure that the belt is "tight enough"? is there a torque setting i have to torque the tensioning bolt to? or is it something i can check by feel.

[Bill R.]

by pushing on the belt in the middle by hand, its hard to describe how tight it should be, but with a modest push of say 30lbs force it should deflect about 3/4 to 1 inch, snug.... It still seems to be a strange coincedence that as soon as you get it back this happens.. I would order a regulator though if everything else looks ok.




at the b+ or higher of the two nuts, i'm running 11.71 after startup. UNLESS there is insulation on the bolt affecting my reading, my reading at D+ on the alternator is 8.76 volts. bill, how would i make sure that the belt is "tight enough"? is there a torque setting i have to torque the tensioning bolt to? or is it something i can check by feel.

[mholbrook]

Brushes are likely replacable on the alternator. Look a the back, two screws hold the brush assmebly/voltage regulator. Remove and look at the brushes. Cheap brush assembly is about $20 and good (Bosch-recommended) is about $50.

Mike

[ryan roopnarine]

the belt as hard as i could and couldn't get more than 3/4 inch of movement, looks functional. sad, sad existence when i have to hook my car battery charger up to my cell phone cig adaptor to call pat and yves for a new regulator, reminds me of too much crappy ham radio equipment i had once... can you give me some info on the firewall battery connection? is that something to do with the remote positive terminal? any particular place i should look, as i have to go identify this alternator before they can ship me one.


by pushing on the belt in the middle by hand, its hard to describe how tight it should be, but with a modest push of say 30lbs force it should deflect about 3/4 to 1 inch, snug.... It still seems to be a strange coincedence that as soon as you get it back this happens.. I would order a regulator though if everything else looks ok.

[Bill R.]

Its snug with no loose wires.http://www.bimmernut.com/%7Ebillr/images/Ryan-1.jpg








the belt as hard as i could and couldn't get more than 3/4 inch of movement, looks functional. sad, sad existence when i have to hook my car battery charger up to my cell phone cig adaptor to call pat and yves for a new regulator, reminds me of too much crappy ham radio equipment i had once... can you give me some info on the firewall battery connection? is that something to do with the remote positive terminal? any particular place i should look, as i have to go identify this alternator before they can ship me one.

[ryan roopnarine]

for one day bill, but which regulator do you recommend? bma has the generic german for $12, or bosch for $35. i'm not one to throw replenishable stuff away, so if i get the 12 one, im going to order two and keep a spare, or buy the bosch and blow torch out the brushes and replace em. remote + looks snug.

[Bill R.]

for one day bill, but which regulator do you recommend? bma has the generic german for $12, or bosch for $35. i'm not one to throw replenishable stuff away, so if i get the 12 one, im going to order two and keep a spare, or buy the bosch and blow torch out the brushes and replace em. remote + looks snug.

[MikeV]

(sigh) y'know, on my mid-engine car the first step to removing the alternator is to remove the cruise-control control box and exhaust mid-pipe..... :(