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1993 STS, 1997 STS, 2002 SLS, 2007 CTS 3.6
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Discussion Starter #1
When I start up it shows a high batt voltage warning and when I check it it's normally around the 16.1 range and than after some driving it goes down some to about 13.5. Should I be conserned or is it ok to continue to drive it. Is it the alternator or voltage regulator (which I understand is built into the alt on these)?

Thanks
 

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16.1 volts is dangerously high. Electronic devices will start failing if allowed to continue. If this voltage is verified at the battery with a meter (not just the car's display), then you have a bad regulator inside the alternator. Nothing else can do this.

Keith
 

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'93 Eldorado
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I have a '93 Eldo, and the voltage is normally at 14.3 or so, however it started jumping up to 16.1 and giving me the "service engine soon" and "high battery voltas" warning, it also seems to lose power and mis-shift when this happens. there was a bad lead off the alt that we replaced, i also had the alt checked and they said it was good but since it seems to be an intermittent problem i wonder if they would have found it. it ran fine for a week and then started doing the same thing once we got into the -0 degree temps, now more frequently (3 times on the way to work this morning) is there anything else that could cause this besides the volt-reg, it starts fine even in this cold wether so i wouldn't think it would have anything to do with the battery correct?
 

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Discussion Starter #5
mattakat said:
I have a '93 Eldo, and the voltage is normally at 14.3 or so, however it started jumping up to 16.1 and giving me the "service engine soon" and "high battery voltas" warning, it also seems to lose power and mis-shift when this happens. there was a bad lead off the alt that we replaced, i also had the alt checked and they said it was good but since it seems to be an intermittent problem i wonder if they would have found it. it ran fine for a week and then started doing the same thing once we got into the -0 degree temps, now more frequently (3 times on the way to work this morning) is there anything else that could cause this besides the volt-reg, it starts fine even in this cold wether so i wouldn't think it would have anything to do with the battery correct?

I would guess the voltage regulator and not the battery. I still have not fixed mine...I start it up and let it run for a little while and that brings the voltage down from 16.1 to mid 15's. If I am at a stop light it will drop to 14's than go back up when I go. The mis shift is from ( I think, someone correct me if I am wrong) the shift solenoids...probably from to much voltage. I have tried a new battery and it didnt work.

I did put belt dressing on and it ran int he 13-14 range for an entire day but havent been able to duplicate that since.

What codes do you get...be interesting to see which once we both have.

Unfortunatly the stealership price for a alt here is 250+ tax. Since the voltage reg built into the alt might as well change the whole thing...just putting it off as I think it will be a tough DIY job.

Try letting it idle for about 10 min or so and see if drops down from the 16.1 range..works for me, I'm doing that till I can afford new alt.

Anyone else?
 

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Your assumptions are correct. A bad regulator is the only thing that can do this, other than an internal short inside the altenator (doubtful).

On the side of the alternator is something called a "D" hole, because it's shaped like the letter D. Shorting the tab in this hole to ground causes the alternator to go to full output. This hole is used to test for a bad regulator (if you have no output).

If your regulator is good, then something is causing this tab to get shorted to ground.
 

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I will try and check the codes and see what i get. I can get the alt at $161 with my discount, otherwise i have seen it run $380, so that is not too bad. Mine tops out at 16.1 and stays there for about 30sec or so, then drops fast down to 14.3.
 

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Keith, will that "D" hole tell me anything if the problem seems to be intermittent like this? or is it only when there is no voltage output?

Thanks for all the quick replies guys!
 

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1993 STS, 1997 STS, 2002 SLS, 2007 CTS 3.6
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Discussion Starter #9
Is it true that you need to get an alt from the stealership as the "auto zone" and other alts will just burn out and die evey six months...I find it hard to believe there isnt a decent after market Alt out there less than 250.00.

I have read some prior posts about the install process, anyone who has done it before..how much of a pain in the ass was it..I can do most stuff on all other cars..water pumps, alt, on my Monte Carlo SS, radiator, on 4 runner etc etc...just leary on this car...takes me longer to do stuff than most people so is it worth it? Whats the book hours on replacement? anyone? Any tricks on the serp belt. I dont have tool for it....thanks
 

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I have the 4.9 so i don't think it is too bad, my (soon to be) brother-in-law did the other work on the car (front struts and brakes all around) and he took off the alt to have it tested - said it was not a big deal (but then he did the front struts in a hour!) it is his discount that i am using, $161 with a lifetime warrenty not too bad. also got the front struts for $68ea, thought that was a damn good deal there.



Realtor1 said:
Is it true that you need to get an alt from the stealership as the "auto zone" and other alts will just burn out and die evey six months...I find it hard to believe there isnt a decent after market Alt out there less than 250.00.

I have read some prior posts about the install process, anyone who has done it before..how much of a pain in the ass was it..I can do most stuff on all other cars..water pumps, alt, on my Monte Carlo SS, radiator, on 4 runner etc etc...just leary on this car...takes me longer to do stuff than most people so is it worth it? Whats the book hours on replacement? anyone? Any tricks on the serp belt. I dont have tool for it....thanks
 

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Discussion Starter #11
Hmmm odd that it spikes and shoots down like that...have you tried the volt meter at the battery yet to see if maybe the display is rwading it wrong? You still have the mis shifting when it drops down to 14.3 volts?
 

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Discussion Starter #12
mattakat said:
I have the 4.9 so i don't think it is too bad, my (soon to be) brother-in-law did the other work on the car (front struts and brakes all around) and he took off the alt to have it tested - said it was not a big deal (but then he did the front struts in a hour!) it is his discount that i am using, $161 with a lifetime warrenty not too bad. also got the front struts for $68ea, thought that was a damn good deal there.
Very good deal....must be nice :)
 

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i am pretty sure the display is right. it only shifts funny at the high voltage. i haven't tried a volt meter because i have only seen it when driving and it does not happen often enough, car would probably have to idle a couple of hours



Realtor1 said:
Hmmm odd that it spikes and shoots down like that...have you tried the volt meter at the battery yet to see if maybe the display is rwading it wrong? You still have the mis shifting when it drops down to 14.3 volts?
 

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Discussion Starter #14
Ahh gotcha...I was thinking only when you started it up it did it. Possible something loose? If not I would guess voltage reg new alt time...I am with ya...kinda wish I had the 4.9 instead of N* for the alt job.

Good luck
 

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The voltage regulator is easy to change. Have a Starter/Alternator shop do it for you. Theirs are much better quality that the Autozone, etc. stuff.

Use a half inch breaker bar for the serpentine tensioner. It should have a slot for this.

Don't ignore a 16 volt condition just because it's only for 30 seconds. Anything greater that a half second or so is too long. You are shortening the life of everything electrical by letting it go.
 

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i thought the regulator was built into the alternator on mine. can that still be changed by itself?

keithkyll said:
The voltage regulator is easy to change. Have a Starter/Alternator shop do it for you. Theirs are much better quality that the Autozone, etc. stuff.

Use a half inch breaker bar for the serpentine tensioner. It should have a slot for this.

Don't ignore a 16 volt condition just because it's only for 30 seconds. Anything greater that a half second or so is too long. You are shortening the life of everything electrical by letting it go.
 

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The regulator module is mounted inside the back cover with 3 screws. The 2 pin plug plugs directly into it. Each of the 3 screws is an electrical connection, so you must be sure to install it exactly as it came out - don't loose the insulators, put the proper length back in the same hole, etc.

When you seperate the halves of the alternator, the brushes will pop out. The brush holders have a small hole in them. Use a straightened paper clip to hold them in place during reassembly. You pull the 2 "pins" out of the back of the alternator as the final step after putting the two halves back together.

The module should be about 20-30 bucks or so, and the brushes another 5. The regular auto parts rarely have these (try Pep Boys). The Starter/alternator shop will sell you them.
 

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Discussion Starter #18
Thanks a bunch for the great info...will post the outcome...thaks again for the help
 

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Well, i ended up just buying the alternator. we pulled the other one out and it did not seem to spin very smoothly and had a little grinding sound to it. Anyway so far so good, votlage is 13.1 - 14.4.

if you do decide to rebuild your old alt, be very careful when you break it open because it is easy to brake off the brushes, i don't know what they are made of but it has the consistency of graphite. but if you are careful you should be able to rebuild it with out any problems and should be pretty easy. Also be careful of the same issue with the brushes if you have to re-clock your new alt, i would recommend having the parts place clock it if needed, as if you do it yourself it will void the warrenty.

Thanks for all the help guys.
 

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This sounds just like the problem I am having with my 94 STS it runs between 11.5 and 14.1 when I am driving its seems good at 14.1 but once I stop it starts to drop quickly. If I am correct its suspose to stay in the 13-14 range (correct me if wrong) I had tested battery and tried one from a diffrent car and it did same thing. The alternator was replaced in late summer,but a cheapie from car quest do you think I have the same problem (junk alternator)
 
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