Any typical alternator surprises?

[RnR]

Now that spring has sprung, I started looking around the electrical system in my '99 Grand Prix, something I had largely ignored previously. A couple things stood out and will need attention:

1) My alternator (a CS130D), while not not wimping out on startup, appears to be putting out 14.8v during idle. I think this indicates an out of spec voltage regulator condition.

2) Probable excessive parasitic battery drain. My inductive meter indicates several hundred mA of drain which I don't totally believe, but my battery does not seem to be holding an adequate voltage after a couple days of non-use. I did do (2) fairly aggressive charge/desulphate processes on this 3-year old EverStart Maxx (from Johnson Controls) a couple weeks ago, so I think there is an external drain current somewhere that needs to be addressed. My plan is to pull the +V lead of the fuse box and put my DMM in line there and start pulling fuses for isolation.

In regard to item #1, as I don't have a spare vehicle or alternator I thought I would pursue a DIY rebuild using a higher output stator and a better rectifier bridge as well. But, I would like to ask if you guys have any general recommendations as to "what to watch out for" when doing a rebuild. I don't want to be stuck on simple problems getting the thing demounted, or opened, or God only knows... I do love to solder things up so I don't foresee any problems in getting a new stator, rectifier or regulator connected up, but the mechanics inside the thing are making me think twice...

 

[Steve S]

Have you load tested the battery?

 

[RnR]

Not yet, Steve. I see merit in regards to quantifying battery condition, but haven't done this to date as the need to fully ID the drain situation is (I believe) a higher priority and have always thought that the load test is potentially hard on the battery.

On top of that, if I eventually drive to an auto store, yank the battery and get it tested, do they give me a drained battery back?!

 

[bmwtechguy]

I have had several vehicles that measure high voltage like 14.8 at cold start-up. Voltage then tapers off as things warm up inside the alternator. I believe the internal regulator incorporates a Zener diode circuit or some such device that eventually lowers the output (charge) voltage to a more normal 13.5 or 14 volts based on temp inside the alternator/regulator.

Check the output or system voltage after it has run for 20 or 30 minutes. I would be surprised if it is still 14.8 volts.

Does the car have an alarm system or remote start? Anything aftermarket should be checked for a parasitic drain first. This is where I usually find the culprit.

 

[RnR]

Originally Posted By: bmwtechguy
I have had several vehicles that measure high voltage like 14.8 at cold start-up. Voltage then tapers off as things warm up inside the alternator.

Sure enough, after running some errands it measured 14v after returning back to the pad. The voltage regulator must have some sort of compensation that makes for the difference. Thanks to your tip, repair then isn't quite so important but I still want to go through a DIY upgrade in order to increase current on demand capability.

Originally Posted By: bmwtechguy
Does the car have an alarm system or remote start?

Yes, the factory alarm system is there; the only aftermarket things I've added were a CB and an amateur radio rig. The CB has a hard on-off switch while the remote ham radio has been disabled due to theft (head-end was stolen).

 

[eljefino]

They say the higher peak alt winding sometimes cuts down on idle amperage. I would concentrate on keeping things cool and using quality parts, whatever those are LOL.

GMs are a few tenths of a volt higher due to the maintenance free batteries; I have also witnessed 14.7v on my own van.

 

[Colt45ws]

Yeah, if you want more amperage I would go with something bigger like see if I could adapt a CS-144 into it.

 

[sciphi]

My 1999 Buick LeSabre with the same 3800 Series II will show 14.5 to 14.7 volts on cold startup. It's normal. After it's been running 5 minutes my voltage is ~14 volts.

 

[mechtech2]

Depending on temperature, 14.8 could be normal.
Add to this the fact that you are probably not using an expensive Fluke meter, and the readings are not NASA certified!

You want to fool with an alternator?
OK. Get new brushes and a regulator, and take it apart.
Get new bearings or grease the old ones.
Clean the commutator.

 

[RnR]

Originally Posted By: mechtech2
Depending on temperature, 14.8 could be normal.
Add to this the fact that you are probably not using an expensive Fluke meter, and the readings are not NASA certified!
Ha! Well, while my Fluke 77 may not be NIST traceable - it gets the job done.

But... typically speaking, how easy is it to get these things off the car and cracked open?

 

[RnR]

Originally Posted By: sciphi
My 1999 Buick LeSabre with the same 3800 Series II will show 14.5 to 14.7 volts on cold startup. It's normal. After it's been running 5 minutes my voltage is ~14 volts.


I have company! Good to know.

 

[mechtech2]

OOPS!
It is a fluke that you have a Fluke - not normal for civilians!

Alternators are not too bad at all.
An air gun is best for getting the pulley nut off. You may have to take it to any station or shop for that 2 second job.
To re assemble, small wire or paper clips are used to hold the brushes off of the commutator - there should be holes for this.
Clean everything, dress and lube what needs it, and you should be fine.

 

[nel]

I had to replace the rectifier bridge on my CS130D this year. It's very straightforward--no need to take the whole alternator apart. The plastic cover at the back pops off, and the rectifier bridge is then accessible for desoldering and replacement.

Two videos that I found helpful:

http://www.youtube.com/watch?v=7PIR-lWGV6U

http://www.youtube.com/watch?v=CqpE9Xxh76M