temporary alternator fix - cheating

[AVIMAX]

My '86 started running poorly and the battery light would come on when the engine speed dropped under 2000rpm. I did some voltage checks at the battery and determined there is a charging problem since I'm only getting around 11V at idle. Took the alternator out and found the brushes in the voltage regulator to be worn and the slip ring in the alternator also worn, in fact worn right down to the base material. I also found while removing the alternator that the fan housing has many cracks and it should be replaced. So a new alternator plus a new fan housing and I'm looking at close to $1,000. I just want to get through the rest of the season and wait until next spring to spend that much. So what could I do temporarily? I decided that if I could get the brushes to make contact with the unworn areas of the slip ring, the alternator should charge and I might get away with it for a little while. So I cleaned up the brushes, then I added some washers under the voltage regulator to shim it up a bit so the brushes would be relocated. I put everything back together, started the car and viola! Charging at 14.28V at idle! Looks like I may have bought myself a little time. Another bonus, the slight hesitation and jerking I used to get on acceleration is now gone. I guess the car had been operating at less than optimal voltage for some time and the DME didn't like that.

[Jdub]

Brilliant! I work with magnetos and can really appreciate both the issues and the fix. Nice job.

[jimthe1st]

New slip ring brushes are really inexpensive given the effort required to remove and reinstall the alternator.

Over the years I have had to replace 2 911 alternators, one come from our host another from Ebay.

BBB Industries 14892 Remanufactured Alternator | eBay

[bkreigsr]

did you re-profile the brush surface at all to allow for the step?
Bill K

[Alan Lindquist]

I've been told that the fan housing cracks are common. They can be there for a very long time without adversely affecting the clearance of the fan. It's something you can monitor with a flex light and dental mirror. Just keep an eye on the development.

Replacement of the fan housing with an aluminum one is around $500.

Anyone experience a fan housing failure? What's that like? Other than hearing a lot of noise when the housing fails and needing to pull over and get towed, what's the failure like?

[porsche930dude]

are you sure the housing is cracked many times people mistake casting marks for cracks. if you can sand them and they go away then they arnt cracks

[Discseven]

AVI... nice fix!

For entertainment purposes, here's a cracked housing. It's out of an '85 with about 330,000 miles on it.








...Once the housing goes out of round enough for the fan to make contact with it, it's the beginning of the end for the fan. In other words, don't allow contact to go on for long in order to save the fan.




Inside and opposite the blister...




Leading edge of all blades look fine. Rear edges... toasted...

[AVIMAX]

No question, my housing has many cracks, but they are not as bad as the photos posted above. The cracks have been there for at least 2 years, probably more. I'm sure the housing will last for quite a while with the cracks, but I figured if I have to have it all apart to replace the alternator, it is a good time to replace the housing with an aluminum replacement and not have to worry about it any more.

bkreigsr - I did not re-profile the brushes. I probably should have, but figured it is a temporary fix, let's just see if this works. It seems to be working fine now and I will leave it until next year unless my battery light comes on again.

[jimthe1st]

Originally Posted by Discseven

AVI... nice fix!

For entertainment purposes, here's a cracked housing. It's out of an '85 with about 330,000 miles on it.


Leading edge of all blades look fine. Rear edges... toasted...

Rear Edges...toasted...

That strangely looks, and fits, like the trailing edge of a boat propeller that has been operated for to long, or to often, in cavitation. On the other hand..was that assembly involved in an engine fire at some time?

[Discseven]

Originally Posted by jimthe1st

Rear Edges...toasted...

That strangely looks, and fits, like the trailing edge of a boat propeller that has been operated for to long, or to often, in cavitation. On the other hand..was that assembly involved in an engine fire at some time?

Jim... my photos have a dark (charred) appearance but that is only due to photo contrast. There was NO fire here.

Avi... even given all the cracks in my housing, there was still significant strength to it. Add the strap around it and I have to suppose that supports it even more.

Below... a considerable lack of respect was applied to free the alternator. There was a little bit of elasticity to the magnesium while tearing into it but not much. Once the housing gave way... it crumbled quickly.






Replacements...

OEM fan (polished and rebalanced) and Vertex housing. I think comments are fairly similar in the Forum about the fit of the Vertex housing to the cooling shroud... the shroud requires minor modification to align the bolt holes that secure the ignition wire retainers and the shroud to the housing. The alternator I had fit extremely well into the Vertex housing.

[rick-l]

Originally Posted by jimthe1st

New slip ring brushes are really inexpensive

Where can you buy slip rings?

[AVIMAX]

Good question, I have not been able to find a source for the slip rings. I'd try to change them out just for the fun of it before buying a new alternator.