Charging Issue, revisited...., not the Voltage regulator Options

[Aaron Cox]

guys,

im having a heck of a time trying to figure out whats the problem. Gen light came on thursday night on my drive home. i measured voltage goin to the battery as follows:
car off ~13 volts
car idling 14 volts
1500 rpm 15.8 volts BAD

i borrowed a new voltage regulator from bill 'grimstead' and it did not rectify the problem.
all fuses are fine. all connections are solid. the belt is on nice and snug

with the car off, the G light is lit
car idling, it is lit, but very dim....
higher the rpm the less bright the bulb becomes....

now that i have eliminated the voltage reg as a failure mode...
do i have a crapped out alternator?

where is the best place to buy a new alternator?

help me before the WCC... i dont want to blow up my optima....

[echocanyons]

my alternator was new as was my regulator and I still had a very dim light that was only noticable at night.
I drove it for over a year without any problems

I attributed it to bad connections but I could never figure out where.

[skline]

I may have a spare alternator here. Have not tested it but it came off of a running car. You can try it if you like. If it turns out to be the problem, it's yours.

[Aaron Cox]

jeff's 2.0 has one on it also....

i figure if im going to be in there....ill go with a new or rebuilt one..... (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
this sucks....

but the battery should never see more than 14v according to haynes manual.... how is it that both regulators are letting it see 16volts?????

(IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

[ws91420]

Almost sounds like the brushes are going on the alternator. If you have been draining the battery 15.8 v @ 1500 could be in the acceptable range if I remember correctly. When the brushes went in mine it did the same thing. They can be replaced as long as all other componets are ok.

[ws91420]

14v is the mean or average voltage that you should see at 2000 rpm with a load (resistance added to the circuit) so you could see a range.

[Aaron Cox]

QUOTE (ws91420 @ Apr 16 2005, 11:15 AM)

14v is the mean or average voltage that you should see at 2000 rpm with a load (resistance added to the circuit) so you could see a range.

ok. so if i go back out to the car, start it up, measure voltage at the battery at many levels of rpm, what voltage should i say "yep...my alternator is effed!"

i was getting ~16v at like 2k rpm.... (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)

[ws91420]

But that is without a load on it. Alt are meant to be load tested for accurate readings. If you are 2200 rpm you adjust a load resistor to have a current flow of 33 amps. That load resistance causes a voltage drop which gives you the voltage. Basic electronics.

[Aaron Cox]

ok. here is the best question yet.....

WHY did my alternator light come on in the first place??? and the subsequently go out the next morning...and now it is always dimly lit when the car is running?

[ws91420]

You have two brushes on that ride on the shaft that picks up the AC current that is generated. Yes I said AC. The diodes rectify the current into DC. The brushes are held in place on the shaft by springs. Last night as the alt heated up the brushes couldn't conduct the current as well. This am all is cooled down but the brushes are still worn that is why the light is dim. On mine if I remember right the new brushes were like an inch or inch and a half. My old ones about a quarter inch.

[Bleyseng]

maybe its a loose fuse....

[Aaron Cox]

welby,

you are the man. thanks for helping me with this....
so a minimium of new brushes are in order.....or just plop in another alternator.....

so..in the meantime, will i be hurting anything if i drive it....? maybe run out the battery if it isnt getting full charge?

[Aaron Cox]

geoff,

i sprung all the contacts and all fuses are good (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)

[bondo]

QUOTE (ws91420 @ Apr 16 2005, 11:34 AM)

You have two brushes on that ride on the shaft that picks up the AC current that is generated. Yes I said AC. The diodes rectify the current into DC. The brushes are held in place on the shaft by springs. Last night as the alt heated up the brushes couldn't conduct the current as well. This am all is cooled down but the brushes are still worn that is why the light is dim. On mine if I remember right the new brushes were like an inch or inch and a half. My old ones about a quarter inch.

The AC is generated at the outside windings. The brushes are for the field, which is DC energized and controlled by the regulator. The more that goes to the field, the more that comes out on the AC side. I don't see how bad brushes could make it overcharge. It could be a bad battery, or it could be a bad diode that's confusing your meter. Got an oscilloscope? (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[Aaron Cox]

i dont have a sillyscope here.... (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)

now we have 2 converging opinions.....



seems like a new alternator is in the cards (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

[Bleyseng]

sounds like the alt is putting out good voltage so it should be a regulator or wiring problem (sumthin loose).

Geoff

[Aaron Cox]

QUOTE (Bleyseng @ Apr 16 2005, 11:41 AM)

sounds like the alt is putting out good voltage so it should be a regulator or wiring problem (sumthin loose). Geoff

ive swapped out 2 regulators... didnt change. i checked all the connections.....

my car is pissing me off.....

[ws91420]

The reading Aaron is getting is false because he does not have a load on it. An alternator must be load tested for accurate results. I was descriding how a alt works wasn't sure where the change from AC to DC occured in the alt just that it went through the diodes.

[brp914]

imho alternators dont go bad by generating excess voltage. I have had the alt light come on due to shorts on the same cicuit that it is on. In my case it turned out to be the engine compartment light. The wire to it had been spliced at some point in the past. Well it unspliced and was dangling down and shorting against the body. For some reason the alt light was especially bright when braking. I've heard where the reverse light wire doing the same thing. Better do a little troubleshooting with your vom and a schematic. IIRC this stuff goes to fuse 9. I wonder if pulling this fuse and looking to see if your alt light goes out would help locate the problem. good luck

[ws91420]

Mine with the bad brushes put out good too at higher rpm but got worse over time. I am speaking on this from personal experence. First thing I did was replace regulator I tested it at AZ and it was bad. Then this problem came later.