73 911 new home, alternator question

[chauser]

Hi All

I'm the lucky new owner of a 73 911!
The car is in good shape overall (I think), some rust in battery compartments and down the fender under the gas tank fill, but not much else.
The car sat for 3 years so I'm working my way thru the fuel and electrical systems now.

I've got a couple of questions re: fuel, alternator and brake MC.

I've got the tank out and largely cleaned out after soaking in marine clean. The weld joining the 2 halves has some rust at the front end, but inside it looks pretty good as far as I can see. My understanding reading the archives is that the swirl pot will not withstand a dip at the radiator shop, so I'm planning to get a second round of marine clean in it and deal with rust on edges. I see POR 15 recommended for rust, would powder coating after sandblasting work?

I changed oil & filter, cleaned plugs, changed fuel filter, poured marvel mystery oil in the cylinders, and turned it by hand a few times. I recirculated cleaner thru the fuel lines by running the fuel pump from a fuel can and then connected line to fuel filter and got the car started! After blowing smoke for 20 min it cleaned up.
No knocks or funny noises.

The PO said he let it sit because the batteries would not hold charge. I am running a single battery (disconnected the passenger side cable. During the initial startup, the alternator light went out (I don't recall it on), but has since come on and stayed on. With lights on etc I measure ~ 11.5 V at battery at 3000 rpm, so I suspect the alternator is gone. I believe this has the external regulator.

Other tests? I checked the grounds (battery, tranny to chasis) and they seem fine.
I'm wondering about shorts. The fuel temp gauge bounced around somewhat in sync w/ rpm, the clock is not working, and the ignition switch does not always engage starter. I always get fuel pump running, but often when the key is turned to fire the ignition it feels like it hits a hard stop and starter does not engage.

One last question (for now) has to do w/ brake MC. There MC has 1 electrical connector, but there are 2 brown wires, both disconnected, hanging there (photo).
Did the original MC have 2 connections and PO replaced and disconnected wires?

Great resource and I'm looking forward to getting the car street worthy before it gets tooo hot here.

Charles

[DRACO A5OG]

Regulator in screwed in by two nuts at the back of the alternator if same as my 3.2.

Welcome aboard!

[timmy2]

3 prong external regulator beside CDI box, possibly a radio supression unit as well.
Haynes manual will tell you for that age of vehicle.

[Porboynz]

On my 1972 the brake light switch is attached to the pedal cluster, looks like the wires to this switch have been rerouted to that later model master cylinder that has a switch incorporated. Without referencing a wiring diagram I would say that you should connect the Brown/White wire to the switch on your MC. Otherwise check to see if you have a switch in the pedal assembly and reconnect as per factory. The starter sounds like it needs a rebuild, at least the solenoid part does if there is no noise at all when you turn the key. If it clicks but does not spin then suspect the contactors/brushes in the starter. The alternator is easy to remove and check the brushes, but maybe the regulator is even easier to check first. The clock? Well lets worry about that later but there are posts on how to clean the contact inside it and clean the mechanism, its probably the electro mechanical Kenzle version like mine.

[Porboynz]

Just a thought, the alternator will not charge if the regulator is not earthed correctly, the relay panel it attaches to in the engine compartment is rubber mounted but should have an earth strap to the earth stud nearby.

[s_morrison57]

Hey Charles, hope the guys can help you out, welcome to the board, thats a nice car, I like that color, can you send more pic's? Where are you located, there could be someone near you.
Finn

[Sunroof]

Congratulations Charles and by all means keep coming to this board for assistance and great support. I will assume by the bumperettes and "swirlpot" in the gas tank that your car is a 1973.5T with CIS, yes?

My fuel tank on m y 1973.5T was cleaned out by a radiator shop and the swirlpot held up well. It was internally coated with "redkote". The outer coating was removed and painted with POR 15 and finished with Wurth rubberized coating for a factory appearance. If you look at the bottom of the tank you have a large internal fuel filter that you should replace or certainly remove during restoration. This extends up into the swirlpot and is critical as a particulate filter.

Go to the "Technical Articles" here on Pelican for good guidance on how to clean your fuel level unit.

Your alternator is nested behind the cooling fan and accessible by removing the fan shroud. Best to remove (be careful), bench test and get working again.

Good luck

Bob
73.5T

[Targalid]

Re the charging system, I had a similar low voltage which turned out to be loose connections at the 14 pin connector. Check the entire fuse box area for dirty or loose connections. You can monitor the output voltage with a meter run through the cigarette lighter if you are in the cabin. Also, it is likely that the voltage regulator is defective after 40 years of use. Mine was black with a 3 blade connector just rear of the CDI box, made by Marchal in France. Replacing it and cleaning dirty connectors in the fuse area appears to have corrected my charging problems.

[chauser]

Thanks for all the input.

The car is a 73.5T, but the PO installed an S engine with MFI - nice!
The fuel tank does have the swirl pot, but it looks like the marine clean has done a good job removing the fuel tar. The upper half of the tank has a brown speckles still, so I'm going to do a 2nd round of cleaning w/ tank inverted to see if this is rust or organics. If it comes clean I may just recoat the exterior after rust removal around the tank lip. I can get the tank sandblasted and powdercoated - would that be an effective anti-rust treatment?


I'm making my way thru all the electrical connections as suggested.

I found the ground connecting relay panel to frame - it appears tight. Should I check for continuity for the grounds? Is it advisable to take some emory cloth to the contact points to remove oxidation?


One of the issues the car has is rust in the battery compartment (I'll post pictures and ask for suggested repairs after work today). I pulled off the fuse covers that are adjacent to the driver side battery, and the lower 4-5 fuses show corrosion due to acid I suspect. Fuses are intact. Suggestions on how to clean the corrosion - baking soda treatment?

I'll have to check the solenoid to see if that is why I don't always get the starter engaged. I don't hear a click - nothing when the ignition does not engage. Memories of crawling under my VW bus with a block of wood - beating on the solenoid - always worked

Thanks for the help

charles

[Porboynz]

Sounds like you are onto it. Might be a bit tricky getting under a Porsche to give the solenoid a thump, less room than a VW. Same solution works though, but it might be the ignition key going hi resistance in the crank position. Rig up a meter across the wire to the solenoid and check for 12V. If you have 12V but no click then its a sticking solenoid. No 12V means check back towards the ignition switch.

Next step for the alternator is easier when you have a known good regulator to swap in. Maybe you can get inside the regulator and check the contacts for corrosion.

[chauser]

Slow progress..

I'm pulling the alternator and it has a fan shroud attached to the rear of it that I did not see in the other writeups on the site or in my Haynes manual.
To disconnect the alternator wires I have to unbolt the fan shroud correct?

[timmy2]

You are correct, it has to come off to access the wiring. Scribe a mark on it and the housing so that you line it up correctly for correct airflow when you re-assemble it.
Did you check your external regulator? It should be on the left engine compartment wall with a 3 pin connector unless someone has upgraded the alternator to an internal regulator style.

[chauser]

Thanks Dennis

The VR tested OK at a shop so I decided to pull the alternator.
The VR has 2 noise suppression capacitors attached - anything I should check regarding those?

I've got the alt out, and I'm a bit surprised it worked given how brittle the wires are.
There was no ground to case. I've got 2 reds at B+, blk at DF, brn and a green. The blk wire at DF was very corroded and frayed where it connected to the spade terminal, and the male spade terminal in the alternator wiggled freely.

Also several of the fan blades have chips and 1 crack. Hard to imagine a bird-strike in an enclosed engine? Should I look for a replacement?

I also noticed the grey+red strip wire from the MFI thermostat (I think, see photo) is bare where it enters the wiring harness.

I'll take the alternator for testing tomorrow.

Questions:
If alternator tests bad is it better to replace, or rebuild?
Do I need to replace fan with chips in blades?
I think I need to splice in a new blk wire. Recommendations for how to best do this? It would make reinstall easier, if one could use some sort of connector for all of the alternator wires where they exit the fan shrouding. Too much current?

[timmy2]

If it was me:
Have a good shop Rebuild the alternator, replace the fan, replace all of the brittle and questionable wires by splicing into the harness at a location where they are not brittle using crimped and soldered connections (bare crimps) Wrap with insulation and re-attach to alternator. Unwrap harness where bare wires exist and repair in the same manner.
Easy for me to say though. I'm an electrician...
Check the radio supression for continuity or just bypass when you are done to see if they are a problem.
Make sure you get a good ground to the engine case when you put it all back together. Remember, Brown is ground in these cars.

[Porboynz]

Plus one on timmy2 recommendations, but my understanding is that the radio/noise suppression capacitors go open circuit or short circuit when they fail, either is bad. Disconnecting them will prove they are not causing trouble. The only wire carrying significant current is the fat red wire so no issues making a good splice in the other wires, plus make sure you fit a decent earth strap from one mounting bolt to the engine case. Looking at the fan, an outboard motor propellor specialist may be able to make it like new, but I would only consider that if replacement is out of your budget. Here in NZ they go for about US$800 ouch.

[chauser]

Good idea re: propeller repair shop - I'll look into that. New here they are $900+ . Fo that I'd fab one out of carbon fiber!

c

[chauser]

The local shop says the alternator has gone south:
-bad rectifiers
-brushes gone
-armature deeply grooved

I've sent it to a shop in PA in hopes they can revive it.

I hear rumors that the replacement alternators w/ internal regulators are not an exact fit in the sheet metal and one gets vibrations, noise because of poor fit.
Any truth tho this?

[pete3799]

Originally Posted by chauser

The local shop says the alternator has gone south:
-bad rectifiers
-brushes gone
-armature deeply grooved

I've sent it to a shop in PA in hopes they can revive it.

I hear rumors that the replacement alternators w/ internal regulators are not an exact fit in the sheet metal and one gets vibrations, noise because of poor fit.
Any truth tho this?

I just changed out a Marcal (external reg.) for a Valeo (internal reg.) purchased from our host. Fit perfect. No vibrations or noise.

[chauser]

Slooow progress

Alternator rebuilt (Stellar, Pitt) - very nice job
New VR (solid state)

Before I reinstall the alternator I'm looking for replacement insulator covers as mine are brittle.
Suggestions for a source for insulator covers and color coded wire/terminals to splice in new leads for the where mine are brittle?

Gas tank is rust free inside. I found a pH neutral Fe oxide chelator that appears to have worked w/o damage to swirl pot. I've got outside of tank nearly ready for bead-blasting and repaint.
It appears Wurth no longer makes the grey stoneguard - anyone know of a source?

Charles

[lynnmacer]

Haynes manual will tell you for that age of vehicle