252 Second Alternator Option

[cwright27]

Hello all, I'm the proud new owner of a 1987 252!  Apparently I have one of the rare birds that only has one alternator.  I was wondering if any of you fellow 252 owners have had a one alternator 252 and installed a second alternator?  Any idea of costs and labor involved?  I have the switch for the second alternator but I'm not sure if it was wired for the second from the factory or if it is just a switch.  It does seem that with all my avionics on (garmin 530) my alternator is struggling to keep up.  Any advice or thoughts?  Thanks!

[Piloto]

Alternators are highly reliable devices. And when they fail it is usually a partial failure (open diode) condition. When there is an open diode condition the alternator is unable to maintain voltage at lower RPM (below 1200 rpm) when there is a load. But at normal RPM (2400) they will hold. A second alternator is only needed if there are electrical flight critical components such as EFIS, electronic ignition or others. Even if there is an alternator total failure the aircraft battery will outlast (after switching off non-essential) the fuel onboard.  Knowing the reliablity and failure mode of these devices I would not spend the money and headaches on a second one.

José

  

[cwright27]

Thanks for the help guys.  I emailed Don and its confirmed, 16k ish just for parts.  That puts it more in the want than need category at this point.....  It would be nice to have that extra juice on the ground when the engine is lower rpm's.  I guess in the meantime I'll be buying a few more batteries!  I'd like to eventually put a traffic avoidance system, a wx receiver for my 530, a ships power bose headset, and a backup electric gyro in.  Not sure if those would increase my electrical load and cause issues down the road.  Once again thanks!

[jackn]

Congrats on your '87 252. I also have an 87 although I have a TSIO-360sb2 engine. You are correct about the second alt & low rpm. At busy airports and IFR you could wait on the ground a while. I would not like the idea of taking off ifr with a low battery.

[Piloto]

Quote: cwright27

Thanks for the help guys.  I emailed Don and its confirmed, 16k ish just for parts.  That puts it more in the want than need category at this point.....  It would be nice to have that extra juice on the ground when the engine is lower rpm's.  I guess in the meantime I'll be buying a few more batteries!  I'd like to eventually put a traffic avoidance system, a wx receiver for my 530, a ships power bose headset, and a backup electric gyro in.  Not sure if those would increase my electrical load and cause issues down the road.  Once again thanks!

[Parker_Woodruff]

Quote: JimR

Call Don Maxwell.  He commented on one of the email lists recently that he just did one of these installations.  I think that he said that it was 16K in parts alone, plus the labor.  Regardless, he'll be able to give you good information.  Congrats on the new Mooney! 

Jim

[Earl]

I have an 86 252 with only one alternator.  My only gripe is at low RPM (below 1.200 or so) it does not charge the battery.  The only time I had a problem was when my battery was in need of replacement and the electrical flickered wile wiating to depart during my IFR training.  Haven't had the problem since.  I agree that there are more important safety features to put in before a second alternator.

[cwright27]

Thanks guys, all good points!  I agree there are more important safety items to put in first.  I guess that when it came time to overhaul I could opt for a factory reman that had the 2 alternators on it?  I wonder if that would add up to the same 18k in just parts.  Anybody ever do this or know if its possible?  From what it sounds like most the parts are engine specific..  Anyone know the price difference between the one vs two alternator factory reman?