Jeev Posted June 23, 2010 Report Posted June 23, 2010 Hello all I am wondering if anyone has some fresh ideas so here it goes: Aircraft - 1978 M20J Problem: After about one hour of flight I loose charge and get a solid low/high volt on the annc panel. No breakers or switches pop, voltage drops of from 14.1v to 12.5 and drains the batt. If I pull the alt breaker and reset it or toggle the master switch i will instantly get charge back (14.1v) then anywhere from 5 to 60min later it will happen again. What we have tried: Repaced the alternator (was found to have worn brushes), replaced the Voltage regulator, replaced the Alt breaker fuse, repaced the master switch, tested the battery and connections. At this point it is getting really frustrating and expensive and I am hoping you guys have some fresh ideas.... Thanks, Jeev
carusoam Posted June 23, 2010 Report Posted June 23, 2010 Sounds like the alternator is going off line, as if... When starting an engine with a dead battery, the alternator won't come on line... No voltage to the field, no magnetic field generation, no voltage generation... Consider taking a look at or replacing the wires between the regulator and alternator. The M20R has a switch for "alternator field". When this circuit is not connected there will be no generation. I would be focusing on that wire/switch/breaker combination that interupts voltage to the alternator field. You seem to have replaced everything but the wire in between.... (Are you able to check voltage on this wire DURING your next flight?) Best regards, -a-
lenblock Posted June 23, 2010 Report Posted June 23, 2010 I have had the same problem. Check the alternator field ground wire. Runs from the alternator to ground. good luck, Len
Piloto Posted June 23, 2010 Report Posted June 23, 2010 I agree also that it could be related to the alt. field CB. Also check the battery master red switch. This is a dual switch that switches the battery relay and the alt. field. Mine had a similar problem and got it fix by cleaning the switch wire contacts and spraying contact cleaner inside the switch. José
Jeev Posted June 23, 2010 Author Report Posted June 23, 2010 Thank you all I will have those checked out... wish me luck
jmills Posted June 23, 2010 Report Posted June 23, 2010 Quote: Jeev Thank you all I will have those checked out... wish me luck
jackn Posted June 23, 2010 Report Posted June 23, 2010 I had a similar problem. Turned out to be a bad connector from the voltage regulator. Good luck
Kwixdraw Posted June 23, 2010 Report Posted June 23, 2010 Also check any ground straps or whatever is the return path for your setup. Sometimes you may have a ground strap from an engine or engine mount that will be loose or damaged. Check the service manual for these situations since it might be some other place.
Jeev Posted August 31, 2010 Author Report Posted August 31, 2010 Yeah sorry I forgot to update. It turned out to be some sort of combo between the master switch and thte ALT C/B. The master was replaced and thr issue was a lot less frequent but still there then the C/B was replaced and problem solved. Even pulled the new Voltage regulator out and replaced it with my old one.... Saved a little money
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