Quote:
Originally Posted by DrDave
Learjetter:
I've read through your symptom list. It appears that you have a couple of things in play here. I think we need to establish some baseline items here. I would like to make certain that the front alternator drive coupling is happy. Stick your finger in the fan of the front alternator and see if it turns past the point of medium resistance. We are ruling out that the two rubber pieces aren't mangled.
I'm concerned about the low voltage at 1000 rpm, even considering that it is being read by less than reliable means. Along that line I am curious about the front alternator that will "drop offline." By drop offline do you mean blow the field breaker? I would like to rule out a diode failure in the rectifier bridge. This is a simple test. With the front engine running and the front alternator online with a medium load read the millivolt AC output. Put your meter on the AC scale and select the lowest voltage setting. I'd like to see a number <50mv. You can do your measurement with your test-leads on the battery preferably.
If we pass those two tests we can dig in further to the fun stuff. I have the schematic for the G model. There is only one Alternator system drawing. Let me know what you find from the above two tests.
We will fix this.
Dave
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DrDave,
I’ve replaced the old and unhealthy-looking diodes, relays, capacitors and resistors in the front firewall circuit board. Replaced warning annunciator assembly. Replaced some very shady and badly corroded contractors with Sky-tec (battery, starters, ground power). Alternators turned by hand meet resistance in less than 1/8 turn.
When running front engine only, was able to adjust Original Voltage regulator to 27.9v. Rear DGR5-1 VR appears to run at 26.5v. Together: 26.5v. Select either offline after both online, you get 26.5v. New battery voltage is 25.4, and DIS light comes on at 25.9v. All annunciations appear normal. Ammeter still intermittently waves slightly and rythymically Even when beacon off. Have not touched or adjusted overvolt/undervolt circuitry. There is no battery pack in the aircraft so I’ve labeled the ALT RESTART switch as INOP.
I’ll try to remember the AC volt test next session. Thanks for your thoughts.