Fixing the alternator problem

Honey Mooney HB-DVN
Flemming and Angela PEDERSEN
Sat 22 Sep 2007 20:02
It was still raining in the morning when Tina drove us to the airport. We hoped to depart today
at noon for Ouarzazate as I hoped that the alternator problem was a loose wire for the alternator field excitation (the brushes had been replaced 6 weeks ago in Iceland). Cowling came off and I checked the tightness of the two connections for the alternators. Seemed tight enough, but I nevertheless tightened them a bit more and started the engine. Still no alternator charging current. So something more complicated. The brush assembly came off, but the internal wires looked fine, and the brushes were put back in again.
So it was either the alternator or the voltage regulator which would need replacement, and we headed back to the terminal to rent a car for 3 days and tried to locate a multi-meter to further localize the problem. Carlos, the deputy director of Alicante airport was extremely helpful. He was also a pilot. He tried to put us in contact with a German Mooney pilot Martin based here and also contacted Iberia maintenance to see if they had a voltmeter. In the end we had to drive to a do-it-yourself shop in San Juan to buy a digital multi-meter and a long piece of wire to measure the field excitation voltage in the cockpit.
Back to the airport again, through security and by the VIP car back to the airplane in pouring rain. A few resistance checks of ground connection, rotor resistance and supply to the voltage regulator revealed nothing abnormal. We checked the field excitation voltage in the cabin with the long wire and it was OK. We then started the engine and everything was working fine: no low voltage, normal charging current. What went wrong? Probably a little piece of dirt at the end of the springs for the brushes had prevented good contact an therefore no alternator field. So we can leave for Morocco tomorrow.