alternator issue?

I have a 1998 model and about six months ago my alternator went out. I replaced it myself with an Ultima remanufactured one. I also installed a new battery since the one I had was the original. The car had been working fine until a couple of weeks ago. First, I would notice that sometimes the car acted like it didn't want to start. Then, last week, I was driving it and it just died. It started right back up and hadn't died since. The alternator was charging fine according to my dash readout (15.1 volts). Yesterday my wife told me that it wasn't charging past 13 volts. When I start it, it will read 12.2 volts. As I drive it, it will raise to 13 volts but never any higher. So, it is slightly charging. I also noticed that the tach was jumping around when the engine RPM was steady. Finally, there is a slight noise coming from the engine area now. This is not a grinding noise like the last time I had to replace the alternator. It is more of a loud hum. I don't want to replace the alternator unless I really have to because it was very hard to get out. So, I am looking for anything easier/cheaper to check out first. I have checked both the battery terminal connections and the alternator ground connection with no fix. Could a spark plug and/or wire replacement help? Or am I just going to have to bite the bullet and take the alternator out again? At least it had a warranty.

well, since it's under warrantee, i'd replace the alternator again. If the problem goes away and stays away, great. If not, then you have another problem elsewear.

I have a 1998 model and about six months ago my alternator went out. I replaced it myself with an Ultima remanufactured one. I also installed a new battery since the one I had was the original. The car had been working fine until a couple of weeks ago. First, I would notice that sometimes the car acted like it didn't want to start. Then, last week, I was driving it and it just died. It started right back up and hadn't died since. The alternator was charging fine according to my dash readout (15.1 volts). Yesterday my wife told me that it wasn't charging past 13 volts. When I start it, it will read 12.2 volts. As I drive it, it will raise to 13 volts but never any higher. So, it is slightly charging. I also noticed that the tach was jumping around when the engine RPM was steady. Finally, there is a slight noise coming from the engine area now. This is not a grinding noise like the last time I had to replace the alternator. It is more of a loud hum. I don't want to replace the alternator unless I really have to because it was very hard to get out. So, I am looking for anything easier/cheaper to check out first. I have checked both the battery terminal connections and the alternator ground connection with no fix. Could a spark plug and/or wire replacement help? Or am I just going to have to bite the bullet and take the alternator out again? At least it had a warranty.


Man.. that stinks. That alternator is a pain to get out and in.
If you have checked the cables on the alternator (+12V) and the
jump stud (The plastic box with the +12V connect in the engine
compartment) and are sure these are OK, the only thing this
could be is the alternator regulator going bad or a bad
connection on up in the dash. The PCM can just cause the car
to shut down if it loses power for a duration. If your battery
is connected up OK, I would find it hard to believe that the
car would have this intermittent type of trouble. You could
run the car without an alternator for a short amount of time,
just off of the battery. The TACH bouncing and the PCM
shutting the car down make me suspicious you have a
wiring harness issue up front there.

Did the PCM report any DTC's ? (check engine light?) If it
loss power or something it usually is somewhat helpful with
it's code. I believe the OBDII unit you have has even more
electrical power diagnostic codes in it than my early '95.

Everything you mentioned does not sound like the battery or
the alternator itself is at issue. When you say the car is hard
to start, is it turning over at normal speed but not starting? Or,
is is sluggish to turn over.

You may also want to check and get TSB 02-06-03-006A, labeled
as "Testing Before Replacing Battery or Alt"

Good Luck... that sounds like it may be more complex than it
first appears.

GuMan

The car was, at times, sluggish to turn over and, at other times, would crank right up.
I took a voltage reading at the jump stud with the car running and it read 12.4 volts. I
am starting to think that the regulator or something else with the alternator is going out
because of the partial charging and the hum that wsn't there before. One of the bad
things on this car is, to check the actual connections on the alternator, you have to
take off several things anyway. I will probably check under the dash and check the
alternator connections this weekend and, if that doesn't work, take it off. Where can
I find this "Testing Before Replacing Battery or Alt" you talked about? Thanks.

The car was, at times, sluggish to turn over and, at other times, would crank right up.
I took a voltage reading at the jump stud with the car running and it read 12.4 volts. I
am starting to think that the regulator or something else with the alternator is going out
because of the partial charging and the hum that wsn't there before. One of the bad
things on this car is, to check the actual connections on the alternator, you have to
take off several things anyway. I will probably check under the dash and check the
alternator connections this weekend and, if that doesn't work, take it off. Where can
I find this "Testing Before Replacing Battery or Alt" you talked about? Thanks.


I know the service manager well enough at my local GM dealer that
they will print them out for me. Depending on how they feel that
day, the local dealer is the only route I know of to actually get the
original TSB document. There are also some subscription services,
like ALLDATA.com, which have them.

One other thing you may want to look at is to park in the garage or
somewhere you can shine the headlights on a wall. A very common
failure mode of the regulators which causes great problems on this
car is voltage ripple on the output. A hand held meter is not going
to show this, as this happens at many tens of times per second.
If you can get an oscilliscope, you can measure that same point to
see the ripple. If the ripple is bad enough to cause driveability
issues, you can usually see it in the headlights. Shine the highbeams
on a wall, with the enngine running at the lowest idle you can
get it to run at. If the lights seem to have any flicker in them, it is
definately the regulator in the alternator and can cause big problems
in the car. If left unchecked, this could cause damage to the PCM.

I went with an OEM rebuilt from www.gmpartsexpress.com for a
better price than any other parts stores models, and I know it
fit's exactly. Tightly, but exactly. Not a fun job.

Good Luck!
GuMan

That GM Parts Express Link is dead this evening. Did they fold up?



I know the service manager well enough at my local GM dealer that
they will print them out for me. Depending on how they feel that
day, the local dealer is the only route I know of to actually get the
original TSB document. There are also some subscription services,
like ALLDATA.com, which have them.

One other thing you may want to look at is to park in the garage or
somewhere you can shine the headlights on a wall. A very common
failure mode of the regulators which causes great problems on this
car is voltage ripple on the output. A hand held meter is not going
to show this, as this happens at many tens of times per second.
If you can get an oscilliscope, you can measure that same point to
see the ripple. If the ripple is bad enough to cause driveability
issues, you can usually see it in the headlights. Shine the highbeams
on a wall, with the enngine running at the lowest idle you can
get it to run at. If the lights seem to have any flicker in them, it is
definately the regulator in the alternator and can cause big problems
in the car. If left unchecked, this could cause damage to the PCM.

I went with an OEM rebuilt from www.gmpartsexpress.com for a
better price than any other parts stores models, and I know it
fit's exactly. Tightly, but exactly. Not a fun job.

Good Luck!
GuMan

Sorry... lack of sleep has caused me to cross
web addresses. It is:

www.gmpartsdirect.com
Guman

I can see that you gentlemen have discussed this subject fully so please excuse my intrusion.
What with the fact of your tach jumping around and having good starts one day and not the next plus the alternator problem.
I would strongly suggest removing the battery connections and cleaning them and the posts with a wire brush or the correct tool, the corrosion may not be visually evident but still be there. The same with the ground wires connecting to the frame and engine.