Oscar Avalle Posted August 29, 2017 Report Share Posted August 29, 2017 Just wanted to share with you something that happened to me last Saturday. It was a great day for flying, so we went to the airport with my sons and got into the plane. I switch on the master waiting for the JPI to come alive... Instead nothing happened. I heard the typical click of the solenoid, but beyond that nothing. I checked the battery, 12.9 volts, checked the solenoid, looked ok. So I closed up the hangar and went home. I received a call yesterday that mu "contactor" was bad. My concern is what happens if the contactor goes belly up in flight? Do I lose all power? Quote Link to comment Share on other sites More sharing options...
bob865 Posted August 29, 2017 Report Share Posted August 29, 2017 Well, solenoid and contactor are the same basic thing. You use a little power to turn on a lot of power remotely. What did you do to check the solenoid? Did you put a meter on the output side with the switch on to check for power or was it just a visual inspection. To answer your question about if it fails inflight. The real answer is, it depends on how it fails. There are a multitude of failures that relays (which is basically what a solenoid and a contactor are) can fail. The quick answer is as long as it powers on, it is not likely to fail inflight. Very low likelihood. I've replaced contactors and relays on equipment(industrial equipment) before, but it's usually because they either, 1)don't turn on when you try to turn them on(coil failed or contacts damaged), or 2)don't turn off when you try to turn them off(contacts welded closed). If you hit the switch and get power you are not likely to lose power unless you lose another part of the electrical system. Hope this helps. Quote Link to comment Share on other sites More sharing options...
Jerry 5TJ Posted August 29, 2017 Report Share Posted August 29, 2017 (edited) Analysis: The 1965 C model schematic shows the power relay isolates the battery from the buss but the generator continues to power the buss. So if the power relay fails in flight but Master Switch remains on the generator powers the equipment but the battery is no longer charging. In planes with the original Delco voltage "regulator" the battery plays an important role in stabilizing the buss so expect even more variation in buss voltage. But you'll still have electrical power. Anecdote: That happened to me on a trip decades ago. I stopped for lunch in Winnemucca with my then 12 year old son coming home from Oshkosh. After lunch -- no starter action. I pulled the top cowl, gave the power relay a smart whack with the handle end of a screwdriver & all was fine. Most things don't get better with abuse but sometimes old school power relay contacts will stick. Edited August 29, 2017 by Jerry 5TJ 1 Quote Link to comment Share on other sites More sharing options...
Oscar Avalle Posted August 29, 2017 Author Report Share Posted August 29, 2017 34 minutes ago, bob865 said: Well, solenoid and contactor are the same basic thing. You use a little power to turn on a lot of power remotely. What did you do to check the solenoid? Did you put a meter on the output side with the switch on to check for power or was it just a visual inspection. To answer your question about if it fails inflight. The real answer is, it depends on how it fails. There are a multitude of failures that relays (which is basically what a solenoid and a contactor are) can fail. The quick answer is as long as it powers on, it is not likely to fail inflight. Very low likelihood. I've replaced contactors and relays on equipment(industrial equipment) before, but it's usually because they either, 1)don't turn on when you try to turn them on(coil failed or contacts damaged), or 2)don't turn off when you try to turn them off(contacts welded closed). If you hit the switch and get power you are not likely to lose power unless you lose another part of the electrical system. Hope this helps. Thank you! I checked it visually... So that was the part that failed. Thank you for the clarification. I was beginning to freak out thinking what would I do if I lose all power... Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 30, 2017 Report Share Posted August 30, 2017 Oscar, You are the third person today discussing a failed relay/solenoid/contactor.... three different threads... Check your wiring diagram for details. The Mooney Master relay and the instrument panel relay work together. One is normally open and the other is normally closed. By doing this, if the master fails, the instrument panel fails closed... leaving all the radios operating. Simple bit of complexity that should keep things working with a single failure... don't let a second failure occur. PP thoughts only. Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
MB65E Posted August 30, 2017 Report Share Posted August 30, 2017 Just make sure it's not the battery. It will do the exact same thing you described. Leave the battery on for 10-15 min. The voltage should still stay up. 12.9 still sounds like good voltage, so it's probably the relay. I chased mine for a week. Ended up replacing the master relay and then the battery. However, My voltage was only 12.5-7 or so. It would fall pretty quick to 9v after about 5min. Dead short in the battery. -Matt 1 Quote Link to comment Share on other sites More sharing options...
bob865 Posted August 30, 2017 Report Share Posted August 30, 2017 22 hours ago, Jerry 5TJ said: gave the power relay a smart whack with the handle end of a screwdriver & all was fine. I worked on F-18s in the marines and you could always spot a sticky contactor. It would be covered with dents where the line guys would smack it to get it to run during startup. 4 Quote Link to comment Share on other sites More sharing options...
Oscar Avalle Posted August 30, 2017 Author Report Share Posted August 30, 2017 Thanks guys, yes I saw that we got three different threads on the same subject with different titles. I would suggest we close this one. Quote Link to comment Share on other sites More sharing options...
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