John Sommerfeld

One more thing to look for: On my 1977 Model J, I continuously received a low voltage light at low engine rpm. When the rpm was increased above 1000 rpm the warning light went out. This was consistent from the time I purchased the airplane and I thought it was normal. Shortly thereafter I experienced an in-flight voltage failure and had to abort the flight. The problem was in the main alternator cable. On the 1977 J Model the cable is routed in a manner that causes it to make a very tight 90 degree bend at the point where it attaches to the alternator. This resulted in a continuous strain being applied to the copper lug on the end of the cable, causing the lug to crack and eventually fail. Inspection of the lug's fracture surface showed only a small area of fresh copper. The remaining area was blackened from continuous arcing along the crack which limited current flow from the alternator. The crack was not detected during routine inspection as the lug is covered with a rubber boot. The fix was to replace the broken lug. To prevent reocurrance, I fabricated a strain relief from a piece of aluminum fuel line tubing. After forming a ninety degree bend in the tubing, I sawed the formed section in half along its lineal axis. Using the inner half of the formed section, I deburred all sharp edges, laid the cable along the I.D. surface, and secured it with tie wraps. The strain relief is positioned near the rubber boot allowing sufficient space to slide the boot back to fully clear the lug. This effectively transferred the cable strain from the lug to the aluminum tube section, and there has been no further problem. John

I have a 1977 J Model that is equipped with Grimes recognition lights and wingtip strobes. I cannot find repacement flash tubes so I am considering converting to one of the the Whelen lighting systems. Whelen has very extensive conversion information to assist in the selection and installation. The information includes both flash tube and led systems, specifications, dimensions, installation instructions, and appropriate 337 and logbook entry information. It appears you may have options for partial replacement if your power supplies are still functional. I suggest you start at the following link. John http://www.whelen.com/pb/Aviation/Catalog%20Price%20Lists%20and%20Manuals/Anti-Collision_Light_Systems_Installation_and_Service_Manual.pdf