When to Replace Alternator?
 

Last Summer, I took my alternator to a local guy to get it serviced (new regulator, etc.) - after having lived for awhile with a fluctuating alternator gage readout. Prior to this service, the gage would typically read about 14 volts or a little higher when starting out...then after driving for about ten minutes the gage would start to fluctuate up and down, generally in a lower (just above 12 to around 13.5 volt) range.

For awhile after servicing, the alt-gage would read fairly consistently at or slightly above 14 volts...but within a couple of months it once again started to waver and fluctuate, and right now its behaving almost exactly as I described above (12 plus to 13 plus volts when warm).

While I know I should be performing lots of other checks first - my general question is this: Do alternators ultimately fail? The reason I ask this is that I'm thinking that my alternator is likely the original one, and thus pushing 30 years...and may therefore be close to the end of its service life.

Are you sure it is your alternator causing the fluctuation and not a bad Volt/Oil gauge in your cluster or a loose connection to that combo gauge? I was having similar issues with my temp/fuel gauge and it was a loose connection. Works fine since I fixed that.

Bad grounds, BTDT.

Do alternators ultimately fail? Sure, the slip rings in ours don't look to be replaceable..... well anything is possible, but not easily.

I replaced mine back in Dec. mostly because it was the original unit. The entire electrical system appears to have become more stable so it's something I would recommend.

Most of the consumables in the alt are replaceable. BTDT. If your going through the trouble why not just take it out and have one of the 10 auto parts places within 10 miles of you check it out before you go done a rabbit hole? It still sounds like a bad ground that is "OK" at cool temps and gets worse when things warm up.

Just looked into it again, and turns out you, can get new slip rings! Too bad I did not find them when I had my alternator apart. That will be a project for next time.

Winner winner, chicken dinner. Resistance. Start cleaning chassis harness contacts/engine grounds and also main line for power. Don't just eyeball them and think because they look good that they are good - disassemble, clean, reassemble and grease. Most of these were dry assemblies by Porsche and other manufacturers. As electrical components and systems age, moisture fluctuations and vibration can take a toll especially on dry points. Any signs of discoloration on cabling (blue/black/dusty on copper) indicate corrosion normally attributed to water incursion. OEM harnesses are notorious for this... they just don't take the care to seal 100% and also things wear out.

Put multimeter across before and after to confirm improvement in ohms. If connectors show any sign of corrosion, then replace with new and avoid butt (crimp) type connectors. The crimp connectors with integrated shrink tube usually work okay in a pinch as they're more weather tight - even so, if it's possible then avoid them. Take 10mins and learn how to run a soldering iron and manage shrink tube.

Depending on your environment and use, I would suggest this service every 5yrs. If the car is garage in the desert, never sees rain and only is driven 500 miles a year then I'd say every 20yrs. It's much easier to maintain the contact points once you've done it one time than it is to trouble shoot and repair as more complex issues present. If it's part of your maintenance strategy then as with anything else such as oil changes, you won't run into failures as often.

Do this...
Since I bought my Turbo a year ago I have been chasing a bouncing temp gauge due to loading and unloading of circuits as well as varied charging levels despite a strong alt and battery.

I just installed the Ice Shark wiring upgrades and was having trouble getting a strong circuit to the starter.* At first I thought it was the positive, but by running cables directly to the starter and found it was the negative that was the culprit.* (despite having continuity between all grounds and the battery) Long story short I tried direct grounds from the battery to various body parts and got the same result with a ground direct to the engine as I did with ground direct to the starter.

The mod is a simple 6 gauge cable, six inches long, connected from the firewall battery direct ground and the end of the valve cover.* I simply used a longer bolt than factory for the fire wall ground and used the through bolt area as a lug for the new cable to the engine.* The firewall connection is actually a built in lug.


I sanded the engine side for connectivity and have a quicker start and much better gauges than ever before.* I also picked up an honest .5 volts from the alternator to the battery as I previously was getting .5 volts less at the battery than what the alternator was putting out.
http://i723.photobucket.com/albums/w...ps94dce61f.jpg
http://i723.photobucket.com/albums/w...ps36e22777.jpg

The Ice Shark kit and 6Ga is the proper way.

I did this with a good battery cable attached the same way as above.
My cable was long enough to get to the alternator bracket.

http://forums.pelicanparts.com/uploa...1401060935.jpg

I also replaced the Positive battery cable end with a military style connection and upgraded the cable ends with HD copper connectors on the OEM Porsche cable. NAPA.

http://forums.pelicanparts.com/uploa...1401061015.jpg

J_AZ

IME, the extra jumpered ground went further to fix my issues than rewiring all else. The jumper running the neg direct to the alternator should not have mattered if the engine etc was properly grounded.

Help a novice out..
How/why does doubling the battery's grounding yield such good results?
And, if the lifting bracket is gone on your valve cover, do any other nearby contact points work well?
(I don't see myself stretching to the Alternator bracket - beyond my skill level)

As always, thanks !

In my case pure overkill.
I started with early 924s and most electrical problems were due to poor design of the battery cables.

J_AZ

Great suggestions all - thanks!

As for grounds...I refreshed all that I could find during an engine-out reseal - but perhaps I missed something.

What I'm thinking is that I'll first check voltage at the battery - with car off and then running - to verify (or not) the car's gage reading. Keeping in mind that other than the gage reading, there seem to be no other symptoms of current loss.

If voltage is truly dropping/wavering as the gage suggests...then I'll re-check/clean the wiring/connections from the battery to starter to alternator. If the wiring looks bad, then I may go ahead and spring for an Ice-Shark upgrade, or at least start with the 6 inch jumper as described above.

On the other hand, if everything looks good, I'll go ahead with a new (rebuilt) alternator.

Therein lies your answer. You are probably not doubling the ground but in actuality finally making one good one after all these years! I'd think the screw mounts into the head that the bracket would normally attach to would work fine as well.

Possibly you missed nothing. I had already run a brand new neg cable directly from the battery to the bellhousing to replace the factory line (along with the big positives and the battery clamps) and that did not cure my issues. The 6 gauge jumper I made still went to the engine and theoretically should not have mattered but it did.
PS you can try before you buy by just using a jumpstart cable connected to the battery neg and clamp the other end to various places on the engine and see what happens. This is how I found that putting a jumper to the back of the engine would be helpful.
Grab your multimeter and check alt output, at the alt when running and then check directly at the starter (as that's where the output goes), then at the battery. In my case before the work I was losing at least 1/2 a volt when cold and more when warm. This pointed me past the alt to the wires. Personally I think there are gains to be had by running the alt pos cable direct back to the battery as allt to starter and starter to battery is a much longer path than necessary.

Basic wiring voltage drop testing
 

I have used this link to test my wiring for voltage drops.

Reduce Warranties with Battery & Voltage Drop Tests | AIM

J_AZ