jleidel

So, after I *FINALLY* got my 80' back on the road, I started doing electrical debugging. I took it out for a spin tonight and I found [the hard way] that the alternator is no longer sufficiently charging the battery. I'm getting somewhere in the neighborhood of 12.1 to 12.2 Volts under power. Idling in neutral [or the clutch in], I'm getting much less... hence, the motor dies.



I've already had the battery in the local auto store, and it checks out good. My real question is, has anyone use the Bosch OEM equivalent alternators on early models? They have an OEM 85Amp and 90Amp model listed. They indicate that you might need to shim it a bit in order to ensure the belt runs true [no biggie there]. Anyone tried it??

6mil928

I'd just do the GM mod.

smudaaar

I am running a paris rhone..... my car is a 1980 928s euro spec

dr bob

There are only a few "wearing" parts in an alternator. Brushes and bearings top the very short list. There are other components that can be damaged like diodes and the voltage regulator. IIRC, the voltage regulator includes a new brush holder and brushes so you can kill to flies with one swat there. Bearings are common parts store parts too.

Most serious rebuilders (not the retailers...) can rebuild yours for you or supply the pieces you need to do it yourself. Keeping the original means no shimming, plus the cooling shroud is guaranteed to fit when you are done. I take lots of pics to make sure the two case halves are in the correct orientation on reassemblt, usually supplemented by a scratch or two on the cases. It isn't rocket science.

Remember that, if your car still has the original Paris-Rhone alternator, you'll need to do a resistor change in the pod to get the correct starting excitation current to a newer-flavor Bosch replacement alternator. There's a TSB on that, included in the Morehouse CD set.

Another option that early-car owners have is to use a modern Delco replacement, one that's self-exciting. Do a little searching here and find some excellent how-to's from Dave (Sharkskin) and others. Cost is reasonable, higher output is available, easy access to the pieces you need to get it all to work.

jleidel

Dr. Bob, thanks for the advice. This one should probably be replaced. The car previously had a nasty oil leak from the cam towers, which soaked the bottom end in crud. I've been expecting the alternator to fail as it was coated in black gold and road goodies. Its probably in my best interest to just replace it this time and rebuild it next time [knock on wood].

I've seen the various threads on converting to the Delco Camaro OEM model. This is somewhat interesting, but I'm always a bit hesitant to port to a different alternator [this is my paranoia from owning older Jaguar... thank you Prince of Darkness].

Stupid question, how does one tell if you have a Paris Rhone model alternator? Bosch has a Paris Rhone and non-PR version... both OEM.

SeanR

John, I'd just get the Bosch replacement from Roger. I can get the order in on Monday and have it at the shop same day. He's on vacation in Destin so he won't be answering his phone this weekend.

jackson101

Take it to your local rebuilder, it's really inexpensive. 10 dollars in bearings and 5 dollars in brushes. Ya, he's still going to charge you 50 bucks.

jleidel

Thanks Sean. I'll holler at you on Monday morning. Tell Roger to get some sun on those pasty white legs!

toofast928

Convert to Delco and never replace the alternator again.
Tony

dr bob

The oil cleans up from the case and windings with (gaddd...) detergent and water, or a little paint thinner and a soft brush if you want to get aggressive. The rebuilder will use a vapor degreaser followed by a detergent wash similar to a dishwasher. You can duplicate the process easily in your own garage. So long as the insulation on the windings is intact, you are good to go. The rebuilt 'replacement this time' that you buy was in another car similar to but not necessarily identical to yours.

The later replacements REQUIRE that you pull the pod and swap in the correct excitation resistor. Fix the one you have and avoid pulling the pod and soldering in the new part. If you are timid about doing the work yourself, have the one you have rebuilt and returned to you. Go directly to the rebuilder if you can. they can usually do all the work and test it for you while you enjoy a beer and a sandwich.

----

If Roger has the correct one available that doesn't require the dash mod, that's certainly a good option. If you don't want to endure the beer-and-sandwich stuff... Support your dedicated 928 parts vendors. Keeping them alive prolongs the possible lifespan of all of our cars. It's darn convenient, actually. Phone call, and the right part appears.

jleidel

The pod is coming off this weekend anyway... have to rebuild the circuit board.
I owe Sean and Roger beers... I'll wander over there with some cold ones later next week. [its nice living so close to 928sRUS]

SeanR

Dude, my volt gauge has been screwed since the day I bought the car. Some days it shows I have some voltage, most days it sits on the bottom of the gauge like a lazy lawn mower. I've not pulled the pod to figure it out because I know the alternator is working. Then again, I refuse to pull the pod and fix the odo until my new dash is ready to go in and I can do all of it at one time.

Now my biggest deal is actually being able to work on my own cars. Ang is still not happy with me that her 90 is up on block because I don't have the 3rd (yes I said 3rd) gas tank installed yet. Issues with the intank pump and my refusal to just stick a strainer in there. Should be done this weekend.

How'd I make this post about me.....sorry.

jleidel

Sorry to hear the boss is angry at you. If you need a hand shoe horning the new tank in, holler at me.

I'm down to the speedo and tach working on mine. I've had it apart once already just to limp it along this far. Ordered a new circuit board from Roger last week to finally do the job right.

6mil928

Mines exactly the same. What a pile of crap. Is a new one available still?