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I had the same experience with my alternator coupling. It does appear that there were a number of coplings that got out of the factory that did not have the proper torque required before slipping in the housing. Slip torque should be up around 300 in lbs. When I removed mine, the elastomer could be turned with my finger. At least, then, I could see why it was taking about 5 minutes after start-up before the friction got the coupling hot enough to finally grab and start turning the alternator. I could just about set my watch on it. I'm not sure exactly when this started. It seems that I had at least 80 hrs on the engine before I noticed the sluggish alternator. So, was it a matter of elastomer quality with a shrinkage problem, or what? I ended up putting a new coupling and a new alternator since it had apparently gotten extremely hot at the coupling end due to the friction caused by the defective elastomer slipping in the housing for 5minutes or more, plus the field resistance was 30 ohms, a lot more than the 5 or so as it should be. Got mine through API in Memphis, and these are approved parts, direct replacements and not new but rebuilt.(Electrosystems). The coupling core value is $500, the alternator is $300. I think It cost me, after all said and done, about $1200 net (60 amp alternator), after core credits. I couldn't believe the coupling costs more than the alternator.
The most difficult part of this is removing the engine baffling and getting the alternator out. The 4 nuts holding the alternator to the engine are very difficult to get to, and should be replaced when reinstalled. A 1/2 in. crows foot socket is required to remove and reinstall the nuts.
If anyone is noticing a delay before the alternator starts charging, it is very likely caused by a defective coupling.
This may call for some further investigation into the elastomer quality issue. Incidentally, there are a couple SBs out on couplings that Continental can provide. I have the at the hangar and can advise numbers if anyone is interested. Bob Young LNC IV IO 550 G engine.
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