IndyMatt

Okay here is the story, I finally got my car back together after doing the TB, WP, Cam Sprockets, Oil Pump Gear And Seals, New Power Steering Pump, Power Steering Reservoir, PS Hoses, Radiator Hoses, Fuel Lines, All New Belts, X Pipe, Porkentensioner, Oil Filler Neck, Water Bridge Gaskets, Brake Rotors, Brake Pads, Brake Hoses, Brake Fluid Flush. I am sure that I missed something in there. Anyway what did you do this winter. By the way the alternator was on the garage floor this whole time and could have gotten water and or degreaser on it. Not soaked mind you but a spray could have hit it.

Back on topic, I got to drive the car last night for the first time in 6 months (whole new car by the way). Anyway, I start with the battery and full charge and volt meter on the dash is at ten. I thought it was odd but figured it was due to the battery or car sitting not thinking anything of it. Drive for about fifteen minutes, no problems. Go home go to take it out and it dies. Put the batter on the charger as it is drained again (I'm thinking bad battery, which I am pretty sure it is toast as it isn't holding a charge). The car is still acting weird, check some things out and the ground was loose tightened it up and it is good to go. Some I am thinking this might have been causing my problems. Fire her up and its good to go for now. Drive again for about 15 minutes and with the wife this time and we are dead as a doornail mid trip. Jump the car and it runs for maybe a minute or so and its a no go. Run home pull the battery out of my DD and get the Porsched home, volt meter still bottomed out with the good battery from my car.

So what is the next step from here? I have a volt meter and can test the regulator or alternator but I have no clue where to start. So what do you guys think?

Mrmerlin

start the car and see if its is charging looking for 13.5 or higher. Test at the battery posts and the HOT post. report your findings.
Check also the belt tension for the alternator

IndyMatt

Will do, I am looking into it more tonight or tomorrow night. First is to confirm that the battery I have now it toast, I charged it yesterday and right after the charge it dropping the charge.

jpuzas

Battery is cheap diagnostic to remove one variable. Got mine at Costco for like $50 bucks. Especially since you suspect you need a new one anyway. Start it up and put a voltmeter on the battery posts. It should be at 13.5V as previous post suggests. If not, since you were working on a lot of things check the wiring at the starter since you were down there. The battery goes to the starter and then a wire goes from there to the alternator. If you left off the wire to the alternator you have your solution. I did this once thinking I was slick because I had one car and a bad starter. So I took out the starter and bump started it to take where I was having it rebuilt. Came out and car/battery was dead. Connected the wire to alternator charged the battery briefly and bump started and was good to go.

IndyMatt

Thanks I will check the wire to alternator. I never disconnected the wiring, as I just left the wiring intact and rested the alternator on the floor. Thanks for all the help guys!

IndyMatt

Whats the symptoms of a bad regulator versus a bad alternator?

Alan

Since on a 928 they are integrated together it makes no difference. On some cars they are separate.

In this case it is for sure the alternator that is at fault from your description - keep the battery charged and do not get a replacement unless you have a very good warranty deal... you don't need it. .

First does your charge light come on in ignition bulb test mode? if no I'd debug that.

Check the small terminal on the alternator - is it connected? if not - connect it (check the wiring from when it was laying on the ground - did something pull loose?

If it is connected disconnect it and see if with the ignition on you get 12v on it? If yes - ground it to the chassis & see if the charge light in the dash comes on? If either of these fails you have an exciter circuit to deal with. If both are OK take the alternator out and take it to a good repair shop for testing, if it is the regulator/brushes they can replace that easily & relatively cheaply.

Alan

IndyMatt

Yeah I am really going to take a close look at the back of the alternator to see if a wire broke or is loose. Does anyone have a decent picture of how the connections are supposed to look?

tailpipe

Check the multy plug by the + batt. terminal front pass side of car make sure all are clean might just be a bad connection might have got bumped with all the work you have done.

IndyMatt

Tailpipe, I have thought about that as well, I put some dielectric grease on it and it made it fit pretty loosely. I am definitely going to go over that connection (wipe excess grease and tighten the connection)and take care of the battery as well. I will be able to do a little bit tonight but not much. I will let you guys know what I find.

IndyMatt

Okay took a good look at it today and removed the alternator and took it to Advanced Auto and it tested as good. Not sure though as the guy didn't look like he knew what he was doing. I cleaned all connections and first checking to make sure they were tight. All connections were intact and everything was where they should be. I reconnected the alternator and the same thing no change, no charging going on. Where should I test for voltage off the alternator? I connected my meter up to the main connection and it read at .24 volts. This was after cleaning the small and large posts on the alternator. I am suspecting that the alternator is dead? By the way the meter does work as it goes up or down depending on the charge of the battery.

ew928

Car running with working alternator - 13.5V plus
Battery by itself - around 12.7V

IndyMatt

Its definitely NOT charging the battery because the reading at the battery is always whatever the battery voltage is, as in it is never above 13V. I just wanted to make sure the alternator was working rather than a wiring issue. I wanted to check at the alternator and when I connected the meter to the large post it was reading .24V.

sidehatch

All that stuff you did to the car,the answer to your problem lies there,theres something you forgot to do after doing all that stuff,try to back track.

Alan

Do the tests I suggested.....

Alan