Alternator problem fixed

[RV6_flyer]

Not sure if would be better to post this under electrical or under maintenance. I guess I will post it under electrical.

Several weeks ago, I found out that my alternator was not working. I had just taken off and was about 1 mile north of the airport with an indicated discharge.

Back on the ground, I started an oil change. During my oil change, I found that I had a blown 7.5 Amp voltage regulator fuse and it was replaced. Investigation found no other electrical problems. After the oil change, I did a run up. The alternator was working correctly. I tried different power settings and turned all electrical items in the aircraft on. I even hit the smoke system to see if it would cause a trip. No fault found. I ran the engine with the cowl off till I got up to 300 degrees CHT.

Back in the hangar, I installed the cowl and readied the aircraft for a test flight. Starting, taxi, and run up all went well. I pulled onto the runway and did a best rate of climb takeoff at 80 KIAS. When I rotated, I hit the smoke system switch. At about 50 feet AGL, the alternator went off line. Flew the circuit and taxied back to the hanger.

Back in the hangar with the cowl off, I installed another new fuse, this time a 10 Amp, I was able to get the alternator to fail on the ground during a run up.

I started trouble shooting using the B&C voltage regulator trouble shooting checklist that I downloaded from the web. I got through the first few steps that indicated everything was ok.

RV-8A builder / pilot Mike ?Hooker? Duggan showed up. He is two hangars east from me. He recently had an alternator problem in his airplane that did the same thing as mine is now doing. We are both using B&C L60 and LR3. I have been using mine for 10-years. (Actually the problem occurred one day short of 10-years.) He had the voltage regulator and alternator bench tested. He reported that after much trouble shooting his problem was the connector at the alternator. He helped me fab a test wire and contact to by-pass the aircraft wiring. Running up the aircraft, the alternator now worked fine. Examination of the contact in the connector on the alternator revealed that there was a very loose connection. The new temporary wire required pliers to pull the contact off the alternator. A new wire was routed in the wire harness from the voltage regulator to the alternator. A new contact was inserted into the connector and plugged into the alternator.

My alternator was wired with ONE wire between the voltage regulator and one contact on the alternator using a 1994 drawing. Keep in mind that my aircraft is now 10-years old and has over 2,050 flying hours. Mike has a new 2007 drawing showing two connections at the alternator.

A phone call to B&C indicates that I should use the newer drawing with a wire going to two parallel contacts. They also said that the connector should be fully populated with all contacts even if there is no wire connected to it as the contacts help stabilize the connector.

After two weeks and 3.5 hours of flying, the problem appears to be fixed.

I would like to thank Mike for sharing the source of his alternator problem. Without Mike showing up when he did, I would have had several days of checks getting to the bad contact in the alternator connector. I am not sure that I would have believed that the alternator contact was the problem had I not seen it.

I am pointing out this problem as I am sure most of us would not think of looking at the contact in the connector at the alternator. The contact was in contact with the alternator but it was not a TIGHT fit. The Fast-On like contact in the connector was touching but it was NOT tight.

Moral of this post: Populate all contacts in your alternator connector even if they are not used. Engine vibration will create lose contacts in your alternator connector over time. Just because something worked for 10-years does not mean that it is the BEST way to do it.

[Rupester]

Good info for us all, Gary. Thanx.

Terry Ruprecht
RV9A, QB fuse

[dan]

Originally Posted by RV6_flyer

They also said that the connector should be fully populated with all contacts even if there is no wire connected to it as the contacts help stabilize the connector.

Great point, and thanks for bringing it to our attn. Glad the fix was cheap! Here's to another 10 trouble-free years with your bird.