Miles968

I recently replaced my battery with a brand new Interstate. The battery seems to be working and holding it's charge just fine. I have been paying more attention to my voltage gauge since the battery has been replaced. I have noticed that the is a wide variation in the readings. Usually, it reads right between 12 and 14 ie 13 volts, this is what I think is the normal reading, right? But, more frequently now it is reading just 12! If it is reading only 12, I am just barely breaking even and possibly draining the battery? Is this due to a faulty altenator? At the time I had the battery replaced, I had the mechanic check to see if I had any excess power drain. The only power drain was tracked to the alarm (only when set) and the minimal drawn from the radio memory, both of which are very minimal/acceptable levels.

Anyway, even with all the accessories on, the altenator should be able to "keep up" and charge the battery, right? My worry is that it is not "keeping up" if it is only just barely reading 12v?

Any thoughts are appreciated, TIA

RajDatta

I think your starter needs a rebuild. There is a DIY kit available that a few of the guys performed. I think paragon-products sells it.
You could also go ahead and get a replacement unit from Porsche with its warranty. It should be too expensive.
Raj

Miles968

"Starter"? or Altenator?

flash968

it is very possible that your voltage regulator is going out - this is a very common problem, and an easy fix, and an inexpensive part - the bosch unit is about 45 bucks and hte aftermarket one (which is working fine in every car i heard it has been put in) is about 15 bucks - both are available at paragon - it takes minutes (albeit some patience) to install

as a test, get a voltmeter and test your at rest , idle, and 3k voltages at the battery - you should be at 12.6 or so at rest and 13+ at 3k with accessories on

if it is your alternator itself, if you disconnect the belt and spin it by hand, you should be able to tell - if there is any grinding noise or bearing noise, it's shot - if it spins super freely, it's not perfect either - it should spin, but have just a little "resistance"

side note - the voltmeters in these cars seem to read about a half volt low

Miles968

Thanks for the info Flash!
Now to run some more diagnostics, now that I know what to look for
Thanks again!

Miles968

Hey Flash,
Do you know where the voltage regulator is located?
TIA

I have run the volt meter and the battery seems to be 12.67 with the car off, While the car is running it is reading 13.77 which seems to be the same and the dash gauge. This all seems normal to me, but after running for a while it drops to 12.0 again

Miles968

I looked up the voltage regulator on my PET program and it appears to mounted right to the back of the altinator itself. I have ordered a new one. Hopefully it will solve the issue. If not, I will probalbly replace the altinator

RajDatta

Sorry Miles, I meant alternator. Sounds like you have the proper place located. With your custom manifold, it might be much easier for you to do this compared to a standard 968. Just a few screws/bolts.
Raj

Miles968

New voltage regulator installed today and it seems to have solved the problem. The dash gauge now reads between 12 and 14 consistantly! The old voltage regulator was worn down to little nubs! This 15 dollar part has been a problem for a long time now and finally it's fixed.

I may have been premature.....I just came back from an extended test drive. It was working great and then it seems to have stopped working? The inside gauge now reads only 12 with no variation with rpm's? I will look into again tomorrow

Randy_J

Miles, the new regulator you installed is doing the job - when starting up, the current draw is pretty substantial and the alternator is recharging the battery. After driving around for a while, the battery is getting fully charged up, and the voltages will drop - depends on the current draws, battery condition, charging system etc.

A real good thing to do however is to CLEAN ALL THE GROUNDING POINTS in our cars. You will find that corrosion, loose grounds, bad grounds all contribute to things like poor charging, dim lights, erratic electrical accessories, etc.

Since you have PET - take a look at the wiring harness for the easy grounds. It will not take you too long to loosen, even clean and reinstall. The big ones to check are the Neg Battery cable to Bellhousing ground, the HL grounds (each HL) the main panel grounds (just above the hood release handle under the dash) and the grounds in the trunk - these are all easy to get to and you will see some results. Just be careful around the bellhousing ground - that 10mm nut/washers can easily fall into the bellhousing (great design - a big open inspection hole at the top! Drop that 10mm nut or washer down there and be prepared to open up the clutch / bellhousing to retrieve it). Use a patch of duct tape and tape over that inspection hole before you even think of loosening that cable.

I definitely recommend cleaning as many grounding points as possible before you go chasing more electrical parts - this is a common issue.

Do a search under the 944 Turbo forum for "Iceshark Cables" and you will see supplemental grounds that Dan is selling to Rennlisters. These are awesome - I've installed many into the 951S and have a complete cable set ready to go into the 968 now.

Good luck!

pilot1

i have the same problem with my s2, after much hunting around, i've decided to sell the car, I've tried all the ideas had experts look it over and there really seems to be no cure, plus ecer since my alt total rebuild my car wont idle at first and will hunt violently dropping down to cut out with the volts dropping to 10v and the revs dropping to 0. there has to be something i can do before i let this thing go... i really cant afford to keep throwing 100s/1000s of dollars at this car with no improvment.