Where did you get them tested and do you know what equipment they used ?

Hints:

1) A handheld tester cannot load test a battery...

2) Testing alternator output requires speed testing with a load...

Checker/Pep Boys etc are not usually the best places to go fot this

What pulleys are on there - and what were the answers to the previous questions

Alan

 

Should he be looking to pull his pod and replace the light bulb and field resistor?

 

the alt is a Autozone Duralast rebuild.
here is the write up i did for it last year ish https://rennlist.com/forums/928-foru...r-upgrade.html

took it to AZ to see how things checked out. battery tested fine, i really did not think anything was wrong with it any, but checking does not hurt.
i had the guy test it 4 times on there load machine. 14.0 volts and tested a new one and they were the same.
im on my way out to reinstall and triple check everything that i can think of. and see what i get.

 

re installed. readings take at battery

Cold no ACC idle - 14.12
COld no ACC 1500 14.18

Cold W/ACC idle 13.76
COld w/ACC 1500 13.99

Hot idle no ACC 13.46
Hot no ACC 1500 13.60

Hot w/acc idle 13.10
Hot w/acc 1500 13.40

not sure what changed but seems ok to me now. gauge still seems lower to me then "normal aka 1 volt off" but as long as i know the batt is getting charged, im good i think.

 

The act of removing and reinstalling may have scraped off some corrosion on your terminals. ??

 

that sounds like a properly operating charging system ,
a good chance you may need the replace the ground strap at the battery ,
and clean the connections .

Note if the hatch floor gets wet after you wash the car then the battery ground will also get wet this will cause corrosion internal to the strap

 

i hit everything with a wire brush wether it looked like it needed it or not. so is a mystery... thanks again guys.

 

I wonder if the battery ground strap should be replaced?

 

do you think its a good idea if i replace the battery strap?

 

I would try to clean it as best as possible before replacing since they are not cheap....

 

You can buy a regular ground cable at Autozone for $7. No real need to buy a genuine Porsche ground strap.

 

If you buy a "regular" ground cable, you'll want to put some plastic sleeve on it to insulate it from the body where it passes out of the battery well and up to the rear apron. Purpose is to alllow disconnecting the strap at the bolt actually isolate the battery negaitive from the chassis.

 

Reviving this post as now I am trying to get system working better. Here are symptoms of my '81-- car had original Marshal unit that was terrible. Upgraded(?) to the paris rohn which I admit was marginally better but main problem still remained. Since I have owned this car the output for lights has been weak with lights on. This is to the point that when at a stoplight after a minute when taking off the seat belt warning light comes on and lights brighten quite a bit. If using a/c at night and stopped the guage (I know notoriously inacurate) will drop to '10' (where it is sitting before car is started) and lights are very much dimmer. Again when leaving seatbelt light comes on and lights brighten up.

When driving (day or night) the guage is always jumping and I have no idea what this means but guage rarely reads over 12. From jump post volts are 13 (cannot remember exact and will have to check tomorrow) Also did not know to test when hot, so for me this has been a very informative post.

A few other questions-- those that have gone the chevy route, what did you do with the outside a/c temp sensor? cut hose and leave? turn hose to front of car for air movement? stick a small fan in it to move air?

As of now I believe I have made a mistake and bought a supposedly direct fit bosch unit off ebay from eagleelectric. The unit sent fit well (no rear cover on) and the posts for exciter wire and power were 30 degree off needing to almost stretch harness past comfort level. When car started guage was zero and alt light on, increase rpm did nothing so removed and took in to have tested -- dead alt.

Paid to ship bad unit back and called being very clear I needed an alternator that had a rear cover (for a/c) and was told unit they were sending would have cover also. Took pictures of both the old marshal unit and the one they sent side by side and described where connections needed to be and orientation of rear cover to use cooling duct. New one arrived (no rear cover) so I said screw it I will make my own. About half way through project it came to mind I was heading to sharktoberfest in the morning and I decided to just take the alt to 928intl and see what was available in the way of rear cover.

Friday I get to 928int and was able to get a rear cover that was close to fiting perfect but would need a bit of 'adjustment' (thank you Tom) When back home began to try fitting the cover to alt. First problem was sourcing correct bolts (5mm reg pitch by 4 3/4") to bolt cover on. Ended up in next town at a rebuilder shop. Replaced bolts and oblonged the mounting holes with dremel a bit and cover fit very close. Using a heat gun I reformed the rear of cover to approximate the one on the Paris rohn cover to clear oil sender.

Now I am ready to try the new alt (I need to mention this is a 120 amp unit) Dry fit with no wiring and find 'damn' not enough clearance for oil sender. Off again and a bit more heat. Cover is now a bit less in height than the Paris rohn, still has internal clearance so nothing touching cover neoprene gasket on and ready for mounting. Try mounting and......WFT still won't clear sending unit. Off it comes again and try fit with no cover. Crap, rear just barelty clears sending unit and binds against a stud from block on motor.

Pull it off and measure against marshal and find the marshal alt body is 3 1/16" and this unit is 4". Absolutly no way this is going to work. Get on phone and call eagleelectric. I tell him what the praoblems are nad says he has sold many and no one has ever had the same problem. When asked about the rear cover he says it is not needed. It took quite a bit of explanation WHY I needed the cover for the a/c. but eventually he understood (I think) His soulution --- send the unit back again (my cost) and he will make it right, or send back his and ship him mine (again my cost) and he will upgrade it.

I really wish I had taken mine to a local rebuilder. This endeavor is passing the fiacoe stage and nearing cluster f%@# zone I think. Going to call again tomorrow and send pictures of oil sender and associated areas and see what can be done.

Wow I really turned this into a rant, sorry about that, but am very interested in input for questions above.

 

The red wire that goes from the alternator to the jump post is very prone to corrosion (on mine anyway) at the jump post end. I've cut it back about 2 inches so far, and still have about one fourth of the strands with heavy corrosion. The next step is to replace that wire.