Can this SEV Marchal alternator (aka Mr. Sparky) be repaired?

[clarkd]

I decided to open up my alternator before ordering a replacement. Heat and time have taken a toll on the wiring/insulation. It threw a few sparks when I took it to the repair shop to be tested. The owner handed it back to me and declined the minimum charge even though I offered to pay. That should have been my first clue!

So far I've replaced the stator/diode wiring, but only soldered the stator connections. Can someone tell me specifically what needs to be insulated/isolated as far as solid wire at the stator? Also, is there a modern material that can be used to "glue" the connections back to the stator? The picture of the bare stator/diode wire connection shows some of the original material on the right side.

The alternator is externally regulated part # 712 237 02 from a 1973 911 E.

[911pcars]

Take it to a real auto electric shop to rebuild.

For DIY, you'll need an electrical schematic of the Marchal alternator.

Best wishes,
Sherwood

[Joe Bob]

I agree....a good shop is worthe money.....plus a warranty.

[HawgRyder]

In the case of some high current alternators...the connections may not be "soldered"...they might be Silver Soldered. This is because of the heat buildup at junctions in the wiring.
I agree with 911pcars...take the unit to a REPUTABLE shop.
they will rebuild it...and TEST it for you...(make sure the test is done in front of you)...note the max voltage and current outputs.
Write down the numbers for later...years down the road...you can check the performance against those numbers and know the condition of the unit exactly.
Bob

[clarkd]

I was fortunate to locate a remanufactured stator for my alternator. My plans are now to use the remanufactured part and rehab and save the original stator. I bought some Spryon insulating varnish, but this remanufactured part appears to have been dipped.

As far as the original stator, I still haven't found any short lengths of coated fiberglass sleeving to use on the stator/diode wiring connections. From what I've learned via Google, the sleeving was secondary insulation and something for resin to soak into and adhere the connections to the top of the windings.



A rectifier plate with original diodes and the cleaned up version with new diodes. Between the two plates, only half the diodes had continuity in one direction or the other.




New Japanese bearings for my French alternator from my German car. Loaner power steering puller from my FLAPS worked great on the bearings. There is a good step by step alternator bearing replacement post on the Rennlist site.




I bought new brushes, but the SEV brush holder has an internal stop so the brushes don't pop out when they are not in contact with the slip rings. I'm reluctant to pry on the old brush holder until I can locate a replacement so I thought I would update the post since I've stopped for now.

One of the slip rings on the rotor has about a 0.010" deep groove. I plan to drop by a machine shop this week to see if the slip rings can be turned down. I'll look for replacement slip rings just in case. I was told the slip rings have to be carefully unsoldered and will be destroyed during removal.



Cleaned up end pieces

[clarkd]

This project finally got knocked out, but not in the most timely fashion.

I removed the old brushes from the brush holder. The scribe mark was made on the old brush at the edge of the holder prior to desolder. By eyeballing how much of the brush is exposed once compressed against the slip ring, I would estimate the old brush wasn't marginal at all. Twice as much wear would have put it in the replacement needed range for this alternator.



Just in case you didn't know (I didn't at first), the brush leads pass through the center of the springs and are looped around tabs on the back of the holder to set the initial depth. The leads are then soldered in place. The picture below is prior to snipping the lead excess.



This was learn as you go for me. I used the post nuts to hold the rectifier plates in place before hand pressing the end piece onto the stator. Next I routed the insulated wires from the stator windings to the diodes and cut/stripped them to length. Obviously it would have been impossible to solder the wires to some of the diodes with the red isolation plate in place.



This rebuilt section was previously the problem area. If you have this style of alternator, next time you pull your fan assembly check for worn/degraded insulation where the wiring touches the outside edge of the rectifier plates.



I had the slips rings skimmed down at a machine shop. It's a father/son shop. I've only been to the shop a few times, but when I walked in this time and said Porsche I learned the son has two complete 914's. He pointed out two other 914 parts cars weathering away outside.



As mentioned previously, I referenced a Rennlist site post on bearing replacement when I reassembled my alternator.

1978 911 Marchall alternator bearing replacement - Rennlist Discussion Forums

I pressed the fan side bearing into the end piece using just wooden blocks and a C clamp. I easily drove both bearings onto the ends of the rotor shaft with appropriately sized sockets and a rubber mallet. I used blue thread locker on the retainer plate screws.

I took my DIY rebuilt alternator to a different "old timey" auto electric shop than I did originally. I'm lucky two of these remaining types of shops are close to where I live. Make sure you take the fan/shaft nut with you if plan to have your alternator tested. Based on my very limited experience, pulleys that will fit are easy to locate, but nuts aren't.

I wasn't quick enough with my phone to snap an actual test in progress picture. Note shop sound system in upper right hand corner of picture.



The majority of my time at the shop was spent talking about old cars and old motorcycles, but I did learn that I have an alternator that "puts out".....ha ha

Here is a picture of the alternator reassembled. Looks clean enough for where it is headed.



I reinstalled the fan/alt housing, made sure the belt had just the right amount of tension and then connected the battery. Why is my alternator warning light on when the key switch is not in the run position and the light off when the key switch is in the run position? It was opposite that way before I originally pulled the alternator. Did I replace the diodes in the red isolation plate?.......No..... Did the alternator output testing turn the old diodes into the equivalent of copper wire?.......Probably. Below is a picture I took while convincing myself that I was choosing the proper bias diodes for the isloation plate.



After getting side tracked for the previous few weekends, I finally got new diodes in the isolation plate and the alternator reinstalled. I made sure the alternator light was on with the key in run before buttoning things up this go round. The picture below is 14.36 volts at the battery and 2500 rpm. Hanging out the door, I took a bunch or fuzzy shots of my multimeter resting on the fender. This was by far the best one! Meter was reading 13.3 volts at idle. Battery measured 12.8 volts prior to starting.



In hindsight this repair doesn't seem that involved. I did have the occasional pause so I could fix a minor screwup or convince myself I was proceeding correctly. I gave up on the original stator and decided to let it R.I.P. in the replacement stator box.

[Hugh R]

Nice, I hope I don't have to go through that any time soon.

[Targalid]

Great job! I assume, since you did not mention it, that the connections were soldered with ordinary solder rather than high temperature silver solder as suggested in the post by Bob Hutson above.

[HawgRyder]

Silver Solder may not be necessary...but with high current units it might be better (longer life).
Having been in the electronics industry for as long as I have (wow...more than 40 years) I don't like doing things twice.
So...for me...silver solder is the way to go.
Bob

[Porboynz]

Very impressive and nice description/photos, well done I salute your diligence.

[ant7]

Great post!
I have done a few Alternator rebuilds over the years, so understood every step you took, and the frustration felt when things dont always go right the first time!
Anthony.

[304065]

How did you press in the diodes? The factory shows a special locally made tool on a lathe. I assume those are the standard 10mm Valeo type.

My Marchals have the stator dipped in Glyptal, same as the diode plate. It's expensive but provides that original touch, will reduce arcing and prevents the stator from rusting

I always thought (and read here) that the Marchal had only a single output diode for D+/61. But your photos clearly show six diodes for the stator and a trio on the output plate, same as the Bosch. Maybe the workshop manual, which shows only a single diode in the schematic, is responsible for that confusion!

Good job! Tagging this one for the future.

[Tippy]

Great informative thread!

[clarkd]

To answer questions and mention one more thing I forgot:

It is probably not a good idea to use standard PVC coated wire to repair your alternator. (Like the yellow insulated wire I initially used in my attempted stator repair above) The black insulation (replacement stator wires above) has the slick silicone feel of high temp resistant insulation.

I did use general purpose lead/tin solder, but it sounds like some silver in the mix would have enhanced the reliability of the connections.

The diodes are 1/2" OD 35a/200v (spec for my particular alt) I started the diodes in straight by tapping with a hammer and deep well socket then finished squeezing them home with a C clamp/socket.

This type of alternator has a single shared 3 diode rectifier plate for both the D+/61 terminal to the voltage regulator and the B+ to the starter/battery. (The other 3 diode plate goes to ground via the alt housing)

Current enters the red plate via the D+/61 post and flows through the red plate into the bodies of the 2 pressed in diodes and then into the B+ post. The B+ post/bolt is insulated from the plate......top, bottom and middle. Pictures below for a visual.

[manbridge 74]

Incredible amount of excellence in your thread.

In other arcane news..... my propane Ford powered farm irrigator uses a SEV Marchal alternator from which I stole the barely worn brushes from to fit my 74 911. We jump irrigator every time anyway.

Functional meeting form back to functional again.

[pavlos]

Am trying to do the same job, but the 2 copper rings on the rotor have been destroyed. Any ideas how this can be solved ? Any idead if I could find replacement rings and from where ?

[turbo951]

A new rotor will come ready to go ..

[pavlos]

Originally Posted by turbo951

A new rotor will come ready to go ..

Thanks Turbo951.

Any idea from where I could get a new rotor ??

[stormcrow]

Where did you get your parts from if I might ask. I just pulled my Alternator out and will be going to check it out.

[pavlos]

Was not able to find rotor replacement yet. I don't know if turbo951 could help with any suggestions...