74' 911 Alternator/Generator

[turizmo]

First of all, it's my first visit to this site...and gosh..i wish i had known this site earlier!!!

I am in the process of learning my 911...so please be kind!! hehe...

I have acquired 74' 911 quite recently and the alternator has gone bad... i think. i have checked the battery load and it had more than half the load. the car does not start unless i do jump start and seems to be on week side and gets weeker if i try to turn on the light.

is this surely due to the alternator?
i read that replacing regulator is also recommanded.

is it fairly easy to replace the alternator by myself? i haven't looked at the repair manual yet, which i plan to do later today.

i have spoken with local shop and they said they will replace it with later model alternator that has integrated regulator, but need to modify housing to accomodate the new alternator and it would cost in the neighborhood of $700 (which i think is ridiculous) any thoughts for that?

your help on these topics will be much appreciated. thx.

turizmo.

[Joeaksa]

First of all you need to get a digital VOM and see what your voltages are. With the motor off, check the battery, then start the motor, again check voltages. Rev the puppy up to 2000 and check it again... turn the headlights and electric defroster on and check it a forth time.

Readings should be:

1. 11.5-12.4 or so
2. 12.6-13.5 "
3. 13.5-15.5 "
4. a bit lower than 2 or 3 but still above 12.6 or so. To do it really right it needs to be charged then do a load charge on it. Most parts houses can do this check if you charge it overnight but a low initial voltage after charge is not good.

Anything lower on your first reading means that your battery is either bad or needs charge. Trickle charge it overnight and retry. Remember that the battery runs the car and its systems on any car, the alternator is just there to keep it charged and in good condition. If you are the least bit suspect, put a new battery in the car as its the heart of any electrical system and not that expensive these days.

Your readings on 2-4 need to be above 12.6 or above to replenish the battery (would really like to see 13+) or you have a duff alternator or regulator. If the voltages drop more than .2 or .4 of a volt when you put a load on the system (step 4) then you again have either a bad alternator or regulator that is not pulling the load.

Replacement of the alternator is not that difficult if you are a bit mechanical and have basic tools. See the pelican tech pages for a blow by blow account. Get your unit overhauled, and it will cost under $100. Mine was under $75 at a small shop in Dallas. It could be the regulator, or the diodes, brushes or armature in the alternator.

There are 100's of thousands of the cars out with the separate regulator and they work fine, so why waste money upgrading to something that Porsche did not feel was needed. I would save your money for other projects but thats my feeling. The shop may be wanting to spend $700 by "upgrading" your alternator but they are also trying to make a profit on you as well...

Your starting problems could be the starter as well. They do drag at times and mimic a alternator problem. No way to tell until you confirm that the alternator is working and charging a good battery in your system.

If you are new to the forum, then welcome! This is the place for help... btw, use your real name on emails... it helps to know who you are talking with!

Joe

[saint914]

Hi, why not look at one of these units. Much nicer than the original ones.

www.aasasales.com

They too have the regulator built in.
Saint

[turizmo]

thx for your inputs!!