smg944

iTrader: (34)

i have managed to blow 3 alternators in the past week. this all started when i replaced the alternator for the first time about 2 months ago. i had a bad regulator and my lights would flicker slightly. so i had it fixed and about 2 weeks ago i got the charge light. so i had the alternator replaced again. fired the car up and had 14.5 volts. got out of the car and let it warm up. when i got back in it read 11.8 volts. once the car was off the battery went right back to 12.4 volts. so i changed the alternator again for the 2nd time. once again started it back up and got 14.5 volts. i sat in the car this time and watched it drop right down to 12.0 v then down to 11.5 v. within 30 seconds. so i then tested all the wiring for any shorts. found nothing.... the car has 80k original miles and all of the wiring is in great condition anyway. but i tested almost every wire going back to the fuel pump and all. i have no continuity on anything. so once again i install the 3rd alternator, this time started off lower at 13.0 then once again dropped to 12.0 but this time would vary from 12.0 to 12.5.

the only thing i replaced after the first alternator was the battery under warranty. is it possible the battery is causing my alternators to blow?

adam c

iTrader: (2)

All ground wires connected properly? Battery grounded properly? Where are you getting your alternators? Quality units? Its unlikely that the alternators are the problem. It sounds like you are wired wrong. Anyone in your area with an FD that you can look at to check that the wires are routed properly?

smg944

iTrader: (34)

checked all grounds everything seems good. chassis, and engine are grounded well. i have used 2 rebuilt alternators from local shops and one mazda unit. i also have my friends fd there he is letting me use it for testing. pretty much everything i checked is the same between mine and his. i expected to be blowing fuses but nothing.

smg944

iTrader: (34)

so i am re checking my grounds today. i am getting .008 volts on the engine and .018 volts on the chassis. this is using a voltmeter with the positive lead on either the engine or chassis and the neg. on the negative battery terminal. compared to the other fd here which is at .000 on both engine and chassis. so it seems i am getting very slight voltage to the chassis or engine.

smg944

iTrader: (34)

also just tested with the key off and it goes right to .000 . once i turn the key on and watching the voltmeter. it jumps to .130 then drops quickly to .018 volts. this is with the positive lead on the chassis and the neg. lead on the negative battery terminal. the other fd here stays at .000 all the time including when the key is turned to the on position. so something is not right....

edit. it is also picking up voltage when the lights are turned on. parking lights are at .04 volts and the headlights jump up to .100 volts.

cesarx7

iTrader: (1)

Don't measure voltage to check your grounds. When checking your grounding points, measure the ohms with power off. The readings should be close to zero. Might as well re-tighten them while your at it.

RotoricanNY

iTrader: (2)

Sounds like you have too much resistance in you're wiring so the alternator is trying to compensate thus over heating and taking a crap, you might wanna check for burned or fried wires, also for rust at your grounds. when the car is running you shouldn't get more than 13.5 volts. But I'm not an expert at electrical, I kinda hate it, so don't take my word for it.

smg944

iTrader: (34)

tested using ohms. came up with 1.3 ohms between the chassis or engine to the negative battery terminal. i also checked from chassis to engine and it was 0.1 ohm.

also did more testing with the other fd and under electrical load like headlights or key on it also jumps up. just not as high as mine in voltage that is. so no progress there. i also checked the ohm value on the other fd. between the chassis and the neg battery cable on his is 1.4 ohms. almost exactly the same.

smg944

iTrader: (34)

so the white and green wire that goes to the alternator connector gives me back no ohm value goes to OFL. on the other fd it reads right about 37 ohms. the continutiy is there also at .050 where mine is at 1.4. so something is not right there. the white and green wire goes to both the fuel pump and the airbag module. i disconnected both to see if that did anything and all is the same.

does the white and green wire go anywhere else?

also just brought the 4th alternator over to another shop and also blown....

RotoricanNY

iTrader: (2)

well if it doesn't give you an ohm value chances are theres an "open" in that circuit.

bajaman

I had a similar thing happen, years ago in my Triumph TR-7. I had an alternator go bad, which would fry my battery into some sort of dead-short nightmare. So I replaced the alternator, which would get killed by the battery, so I replaced the battery but...the new alternator had suffered already and...it would kill the battery.
I went thru this EXPENSIVE cycle (for the record, a TR-7 alternator was over $300 in the early '80s) until I replaced alternator and battery together. Problem fixed.

Uncle Hungry

iTrader: (2)

Get your battery load tested

smg944

iTrader: (34)

also the tests i just made were with the battery disconnected. with it connected i get voltage to the white and green wire and the wire that bolts to the alternator, which seems normal with the other fd. i only get a different reading when the battery is disconnected.

smg944

iTrader: (34)

so i got a 3rd fd there today to check more wiring. my wiring checked out the same as this other fd. so finally i installed the 5th alternator on there and it WORKED!! . so my wiring was fine from the get go. the problem came from a brand new maita battery that i got at autozone. i brought this one back after the 4th alternator blew and i couldnt find anything wrong with my wires. the alternator shop said it is very rare but the plates inside the alternator could have been shorted. finally..... also thanks everyone for the imput.

bajaman

Good to hear all is well again!