Alternator Failure?

[Lorenfb]

"Loren...do you know anyone in South Bay that does alt. rebuilds? I live in Redondo...."

Two Options:

1. Call Pelican. They can probably provide you with one at a good price & warranty.
They should have an exchange program. Call Tom Gould.
2. Call some of the many Porsche shops in the South Bay and ask them.

Make sure that you get the lastest OEM regulator from Valeo/Paris Rhone
(no more aluminum fins). Pelican should stock this one.

[tt_targa]

I am sure the alt light comes on with under charge. Does it come on with over charge?
Anyone?

[LakeCleElum]

Nope....

[Groovy911SC]

My car was at a shop being corner balanced aligned etc when the guy called me and said my alternator is bad. The battery died while refilling the oil after the change. They wanted $600.00 to replace the alternator so I decided to do it myself. I can handle this right? I recently rebuilt the engine and did all the work myself. The car has only been run to break in the engine and driven on the street enough to correct oil leak etc. Since I just rebuilt engine, it is entirely possible that I re-connected it incorrectly. The shop stated that the battery was not re-charging (new Interstate Battery) that much is true but didn't investigate if the connects were properly done.

I removed the alternator and took it too a shop who rebuilds these units. Today they called and said nothing was wrong with the alternator. I know something is wrong with the car as the battery can be re-charged (manually) and driven. the battery will go completely dead if I let it.

I will re-install the alternator this evening. Can anyone give me guidence on what to check and what to look for? I do have a mulitmeter. I'm really not skilled with voltage etc, so any basic information will be helpful. I know to check voltage at the battery but that is it.

[Gunter]

Have a automotive electrical shop test the battery,i.e., put a load on it to see if it is kaput. Even a fairly new battery can go bad. Call the shop who told you that the alternator was bad and tell them the news and see what they have to say what the problem could be. Keep in mind that they made the wrong diagnosis.

[Wil Ferch]

If you do decide to tackle the R&R yourself...see here--->
http://www.pelicanparts.com/techarticles/911_volt_reg_replace/911_volt_reg_replace.htm

Wil

[ruf-porsche]

Sonic

Make sure you recharge your battery fully before reinstalling a rebuilt alternator.

An alternator is not designed to recharge a completely flat battery, so don't get someone to jump start your car. Doing this will only ruin your rebuilt alternator.

[Joe Bob]

Fully charge battery....check to see if alt light comes on when ignition is turned on...important as the bulb is part of the charging circuit.

test battery at rest 12.5v
test battery at idle 13.0-13.5
test at 2500 rpms 13.5-14.5 MAX

too low at rest...bad battery
too low at idle...alt
too high at idle or 2500 rpms...most like a regulator

Porsche alts are not magic...local competent shops can rebuild them.

[ASD]

My 78 SC has the jumping tach indicating overcharging, right?

I changed out the reg for a new one, it seemed better but is back to overcharging again. The gen light comes on a little at idle. I checked charge rate..it starts at 12.5 or so, jumps up to 14.5, then spikes at 17. Could be the alt? My grounds are ok, and I checked belt tightness, and shims, although I am short one shim . Any other ideas before I pull the alt?

[scottb]

Classic symptoms of a bad alternator. It may have taken out your new regulator, too.

If it were my car, I'd pull both out and have a local rebuilder bench test them. While it's apart, now would be a good time to polish and powdercoat the fan and fan housing.

Good luck.

[Early_S_Man]

Spikes above 14.5 Volts are ALWAYS a problem with the regulator, or ground/power cables.

[RoninLB]

Originally posted by Groovy911SC


I'm really not skilled with voltage etc, so any basic information will be helpful. I know to check voltage at the battery but that is it.

Hey Groovy. What's happening?

[Groovy911SC]

RoninLB,

Symptoms are battery did not recharge after I put my newly rebuilt engine in the car. Battery is a new Interstate unit. Battery has been taken to Interstate and tested, it tested fine at Interstate. Local Porsche shop told me Alternator is dead. I took the alternator out myself after I picked the car up from the shop. I tool the alternator to an alternator/generator repair shop where they originally said alternator checked out fine. When I picked up the unit the technician told me the alternator had a "bad spot" and that could have caused the battery not to recharge.
Before my engine rebuild the tach did spike up on rev'ing the engine. I thought it odd but did not know the cause. For the rebuild, I used the original alternator. The tach still spiked up on reving the engine after the rebuild.
I will get the rebuilt alternator in the car this evening (weather has been hell here) and what I wanted to find out is what components should I check? Like I said I know to check the voltage to the battery like ASD did in the above post. How should I check the regulator? Can I check the regulator? The transmission ground cable looks like hell. Possibly a ground issue?
Are there any good automotive electrical books out there that focus on Porsche?
I have new SSI's with a Monte dual in dual out! Sounds groovy when it runs : (
Sorry for the rambling post. Thanks for the help!

[Gunter]

Ground straps are often neglegted; get a new one and check the connection coming from the body to the negative battery post.

[rick-l]

Originally posted by Lorenfb
"They've used the old regulator
which is highly prone to overcharge.

What's going to wear out in a regulator? It's just a couple of transistors diodes and resistors. If the alternator is tested after you put new brushes in it what could go wrong? It is definitely past the infant mortality stage.

[RoninLB]

Originally posted by Groovy911SC

what I wanted to find out is what components should I check?

How should I check the regulator? Can I check the regulator?

The transmission ground cable looks like hell. Possibly a ground issue?

Are there any good automotive electrical books out there that focus on Porsche?

I have new SSI's with a Monte dual in dual out! Sounds groovy when it runs : (

Buy asap "101 Projects for Your Porsche by Wayne R Dempsey" from Pelican Parts. They've heard of this guy Dempsey before. On p61 is "Alternator Troubleshooting and Replacement"

12v electrics are basically all the SOS. If you understand an issue you can translate it to any similar system. Different books will explain and address the issue a bit differently once you get beyond the basic. Auto, marine, and aircraft 12v books all have something to offer. The issue eventually becomes what you want from your electrics beyond the basic. What electric install makes you comfortable beyond stock. I'm not a good example to follow because my basic premise is that our 911 electrics suck to start with. If you want some electric readings, per my suggestion, you're gonna start down a slippery slope. Maybe start with Dempsey's 101 Projects and then stop at a local speed shop for the $15-$20 elec books they have. If you get tickled it'll be text time.

For example of my attitude.. you need a good alternator ground. Our stock ground is the engine case. Bingo suck #1. It's good enough for the factory but it's not good enough for me.

Monty singing a cam with overlap is groovy music imo.

[ASD]

Thanks guys for the insfo, I pulled the fan and alt and reg today and I am taking to get bench tested and see where I am at tommorow. The alt came off the fan easily with a light tap on the screws. The hardest part was getting behind to pull the alt wires , kinda snug in there.

I polished out the fan some with good aluminum polish, and it looks pretty clean, but I am checking out the photos of ones on this site for ideas.
Hope the alt fix will solve the problem I have had.

[ASD]

Had my alternator(paris-rhone) bench tested, turns out it is fine. It has the internal vr ( duh...I didn't know) and I had an external vr plugged in too.
I had replaced that one sometime ago thinking it was bad...
since it was always there ( I have had the car 13 yrs) who'd have thought it was the wrong hookup?
Guess the two regs worked ok until the one on the alt heated up too much.
They are replacing that one, I have disconnected the external, and the alt will get new bearings just in case.
meanwhile I have a detailed fan and painted housing.
Hope all will be well when I put it back together.

[ASD]

OK got my alt and new internal voltreg back. Before i put it all together, a question- I seem to have a hard time getting the shims to lay flat and line up when screwing down the big fan nut. What up with that? Is there some trick to putting the shims back in right?

[Sonic dB]

ASD: Use Vasoline or some Grease to stick the Shims together....then push them in place.

BTW... My 2nd rebuilt Alternator has worked like a charm. I kept the first one that they shipped with the bad diode. I am going to have this one rebuilt as a spare.