TheeMike

2002 Automatic (not Z06)

Started Saturday... Driving along and AC was not putting out air, pressed the button and it turned back off... then my traction control/ABS lights come up... then my radar detector tells me "Low voltage"... I look down and it is about 10.5-11... Not good. I almost made it home (short by about 2 miles). Figure it was the alternator so I called around and no-one had one (I woudl have replaced it by the road if they did). Had the car towed home and pulled the alternator and took it up to Advance and had it tested. No problem found. Brought it back home (had the battery already charging) put it back on and she fired right up and went to 13.x volts. Drove up and had my system checked and all was good.

I have been driving with my voltage up on the DIC for the past 3 days and all looked good. Fire up the car and a few seconds it goes from around 12 to 13.x so I figure maybe just a loose connection and removing it and replacing fixed it.

Driving home today, I look down and it is at 10.5 volts... Oh no, not again! This time I was a little hot headed and put my foot into it a little bit and BAM jumped back up to 13.x...

I am wondering if that clutch in the alternator is bad? I have never seen a clutch in an alternator so I do not know.

Battery is only 6 months old and everything tested fine...

The weirdest part is that she started running fine after giving it some more RPMs... It pulls my thoughts from electrical to mechanical.

I have checked all the connections and grounds. They seem good.

I have read one other guy having this issue but it was solved in a PM so I have no clue what was done.

Any ideas?


*** I did just see http://forums.corvetteforum.com/c5-t...tor-probs.html and wonder if I am having the same issue... Like I said, it takes a few seconds for the alternator to "come on"

jcgunn

Probably bad alternator or loose cable...but you might check the tension on the serpentine belt, if the tensioner is loose/bad that could be an easy fix

TheeMike

I have some play but not much in the belt (probably 1/2 to 3/4 inch)...

TheeMike

Doing some more research I am now wondering if it is a starter/connection issue. I did not realize that it runs via the starter. I had it replaced a few months back and had one of the wires "fixed" as it was corroded. I did have a click a few times today in starting it but chalked it up to the charging issue. Now that I have read more it may be the other way around. (by "click" i mean you could hear the solinoid but no start... clicked it a few times and she fired up)

Now I miss my garage as it is raining and I cannot check this... ARGH...

I will probably drop it off tomorrow with the guys that did the starter and have them recheck the connections (they are a small local shop that do me right, so I hope they will this time)

Is my reasoning sound?

dgrant3830

Check the starter solenoid cables as that is where the alternator connects to the battery.

Bill Curlee

There have been several people who have had bad alternator clutches.


I would also remove the battery cables, clean them and reinstall. Torque to 11 ft/lbs.

Check the solenoid connections on the starter. They come loose a LOT:

TheeMike

Well, I had the lugs checked and all was good and tight.

I replaced the alternator and got the same low voltage readings so I returned that.

I had the solonoid "click" again today (3 or 4 times turing the key then finally started) This is a starter that is only 4 months old and showing the same problems as before I replaced it. It actually did the click a few times shortly after I got it but was not too bad. Now it has done it a few times in the past couple days.

Got to girlfriends house and then the voltage dropped again. Now I had my volt meter so I checked... alt at 13.5 but battery was at 11.3 (close to DIC). Since I was in a good spot, I jacked up the car and "jiggled" the wires at the starter, looked at the DIC and it was up to 13.4 (I am hoping that it was due to the "jiggling" and not just coincidence)

So I am thinking the issue is between the alt and battery. When combined with the starter issue I am now thinking that it could be a bad wire/connection from the battery to the starter. To me, it makes sense... Does it make sense to anyone else?

In this line of thought, is there any reason I could not wire directly from alternator to the battery and from the battery to the starter as 2 seperate things? There does not look to be anything else connected in that circuit.

Thanks for everyone's help...

Mike

TheeMike

Find out the guy that told me the lug on the starter was tight LIED to me...

Figured that I would wire from alternator to battery and starter to battery seperately. When I did finally get to the starter lug it was finger tight... I was a little upset...

Finished running the new config and she seems stable now.

I have noticed that when idling in gear (and it drops below 500rpm) that the voltage dropes back to 12.5 or so, but as soon as it goes above 500 she is back to 13.5+. I think that right now I have too much data. Before I would periodically look at the guage and not pay any attention. Now I am watching the DIC and any little blip is being noticed.

I do now have the same voltage at the alternator as I do the battery so I am happy with that. The DIC consistently shows about 0.2-0.5 volts lower but I am not freaked out about that.


Thanks for your help as always!!!!!

dgrant3830

Its going to take a while to get the batter back up to full power. You should consider connecting a charger to it or a maintainer for a while. Normal voltage indications are 13.8-14.1

PEERPSI

Are you saying the belt deflects 1/2 to 3/4 inch in the middle of the span?

TheeMike

I had it on the charger all night last night. Started at the 10 amp setting for an hour or so (the needle started about 8 and went down to 1-2) then ran it at 2 amp setting over night. I would think that woudl be enough, wouldn't you?


I am wondering if this is really an amperage issue. I put a new alternator on but it did the same thing as early on, but, now that I think about it that was before I found the loose wire at the starter. The starter they gave me through all kinds of "charging system failure" so not an option to try that one again.

I think I have had 2 issues. the first was the bad connection at the starter which dropped the battery to the point that the car shut down. With that issue the voltage varied wildly, 13.8 to 12.7 and below. It woudl stay at the low voltage until something "jiggled" the wire. I did the "big three" and ran the alternator straight to the battery. now it is small fluctuations that are expected like .3-.5 when brakes are pressed but immediatly back to 13.x. When I drive a good distance she charges (SLOWLY... maybe 0.1 volt per 15 miles) or just holds steady. In town, she drains much more quickly. For example, I left work at 13.8 volts went into town and back making 2 stops, some traffic and using brake lights and turn signals... maybe 5 miles total she was down to 13.4 when I got back. Drove her home (only one light and 20 miles of open 65+) and she was back to 13.6. Sat in the driveway and let her idle up and went to 13.7 (the numbers were via the DIC, VM shows constistant +0.2 volts higher as expected)

Battery shows mid 12's when turned off.

My thought is "quick to drain, slow to charge" seems like an amperage issue. Could the short at the starter have messed up the voltage regulator and now she just pushes enough amps to barely cover what is needed? (I am thinking much more is needed in town with stop and go than on the open road)...


I found out that there is an alternator shop just a few miles down the road in the country (only open m-f 8-5 of course). I am hoping they can do a much more thorough diagnosis than Advance Auto can (it tested "OK", but the guy said it had some "odd" showings).

Any chance that I am thinking right here or am I wasting time trying to take off and get it there? Anything I should ask them to do or test that is out of the ordinary?


Thansk...

dgrant3830

Well, its a computer controlled alternator. The pcm issues the charge commands to it so its not like a normal alternator. Battery in the mid 12's is just fine. A new battery will usually show around 13.1 new. The normal minimum is 12.5 static.

PEERPSI

Batteries are 2.2 volts per cell with 6 cells giving a maximum voltage of 13.2. At 12.5 when sitting for a bit I won't be too conerned.

TheeMike

Ammeter shows 2.8 amps off the alternator with ac and high beams on. Girlfriends van shows 20 with no lights...

PEERPSI

What amp meter? If you know how to use an multimeter you could disassemble the alternator and check the 3 phase diode bridge. Often that's the problem with low output. There will be six diodes. When you test them with an ohm meter they should show high resistance with the leads one way and low resistance with the leads reversed. This should be the same for all six diodes in the bridge. Also check the condition of the slip rings and brushes, although that is least likely to be your problem. Should you find yourself tearing it down do replace the bearings. To get the pulley not off use an air impact while holding the pulley with your hand or in a vice.

TheeMike

I borrowed an amp meter from work. One of those clamp types that you put around the wire.

I will check the diodes tomorrow (weather permitting). So if the are bad they will have the same resistance in both directions or no resistance at all? Can I get replacement diodes from radio shack?

PEERPSI

Some clamp on's don't do DC and some have to be used in the correct polarity. I hope you had the right one.

http://www.allaboutcircuits.com/vol_3/chpt_3/2.html
Link to how to test a diode.

Image of how the rectifier system works in your alternator.

TheeMike

Thanks...

I did buy a new VM last night that has a clamp on amp meter that works in DC... Live and learn, right?

Best I can tell is there is about 2 amps difference from the cable from the alternator back to battery vs. the cable from the battery to the fuse box (at idle in park). Not sure if this is the best way to check.

I am going to try to look at the diodes today... (THANKS for the info on diodes)

Mike

TheeMike

I am at my witts end here.

I have had the alternator rebuilt today (it needed a new clutch as well).
Ran 4 guage cable from battery to starter
ran 4 guage cable from battery to alternator
ran 4 guage cable from negative on battery to block and block to frame
(I did remove the stock cables from battery to stater to alternator)
Taught the car what idle means
new battery
new belt
cleaned the intake to within an inch of its life
i checked the 2 fuses by the battery for the ignition switch issue and they read the same as the battery. (16 and 23... 12.11 and 12.13 when battery reads 12.15)... brand new battery and I have been testing so it is a little low.

When I am on the open road she charges slowly. for example, if it starts at 13.4 it may be up to 13.6 after 20 miles or so. When in town she drops much more quickly.

When AC comes on voltage drops and then right back up. same with reverse and brake lights. (looks like brake lights pull an extra 6 amps or so, more when they are initiated but too fast to read goes back to about 6 over what was there without)

I have checked the wire going to the fuse box by battery and the alternator consistently is about 5 amps higher.

Check voltage difference between battery hot and alternator and is less than 0.2 volts.

Alternator shows very low resistance when checked to the battery.

If i pull the 3 wire connection off the alternator and then start (of course i get the charging system failure) but no difference in voltage or ampergae. So, i figure not the PCM. I did the no-no and tried to test the alt unhooked from the battery and got no voltage (very little like0.5 if i remember) so the car is smarter than me.

I am well versed in charging technology now... LOL... but still having the same problem.

nothing seems hot, I do not see any fuse blown.

Any more ideas?

PEERPSI

So I'm not quite sure what you are saying here. You used your DC clamp on ampmeter and measured the current coming out of the alternator, correct? Then you measured the current load to the fuse box from the battery, correct?

They may well be a difference. The current going to the fuse box when subtracted from the alternator current would tell you the charge rate of the battery.

What exactly in as few words as possible is the problem you are having?