JetSet1967 Posted December 20, 2012 Report Share Posted December 20, 2012 Im installing a plane power alternator on my M20C. Replacing my generator. My question is on the voltage regulator there is a field wire, gen wire and a bat wire. Behind the voltage regulator in the Avionics bay is a shunt with the with two large wires and two small wires (the small wires have fuse links. On the generator there were two wires one large and the field wire. The large wire went to the voltage regulator and the field wire went from the gen back to the fire wall (not sure where it went from there. I have run all new wires to the alternator and the voltage regulator that was supplied with the plane power kit and installed it per the install instructions. I would like to use my amp meter in the cluster gauge what do i have to do for that to happen. Quote Link to comment Share on other sites More sharing options...
1964-M20E Posted December 20, 2012 Report Share Posted December 20, 2012 well if i recall correctly the two small wires on the shunt are for the ammeter. Most likely you have a 50A generator now alternator breaker. Unless you are adding a large load there is no need to repalce the breaker. This breaker carried all the electrical load on your plane before. The small wire from the generator is the field wire. You should be installing a new 5A circuit breaker (CB) switch for the alternator field along with a 1A CB and indicator light the you follow the wiring diagram you should not have any problems. Quote Link to comment Share on other sites More sharing options...
moodychief Posted December 20, 2012 Report Share Posted December 20, 2012 The two fused wires go to your cluster gauge. Quote Link to comment Share on other sites More sharing options...
jamesm Posted December 20, 2012 Report Share Posted December 20, 2012 What is year is your M20C ? I have a '67 M20C which has a plane power alternator installed. I did this conversion several years ago. This was done a few months before Plane Power had come out with their generator to alternator kit . I used a Zeftronics voltage regulator for my Alternator installation. I didn't have to touch the Ammeter wiring for 6 pack engine instrument cluster gauges, The ammeter it is still in the circuit. However I did wind-up replacing all the wires in the field circuit since they were the original wires and very frail at terminal end(s). The original fat "BAT" and "GEN" wire(s) that went to the generator voltage regulator terminal(s) on the firewall . I mounted a inline RF filter (Mooney P/N 880014-501) used on later model (1968ish ) Mooney's that had the Prestolite Alternator installation. So one end of the RF filter has the "BAT wire and the other end of the filter has the old "GEN" wire. My Alternator voltage regulator is now mounted inside the cabin just off front passenger left knee behind plastic interior cover. Hope this helps, James '67M20C Quote Link to comment Share on other sites More sharing options...
JetSet1967 Posted December 20, 2012 Author Report Share Posted December 20, 2012 so just for clarification....the old field wire can be removed? And if i follow the wiring diagram the amp meter will still work? Quote Link to comment Share on other sites More sharing options...
jamesm Posted December 20, 2012 Report Share Posted December 20, 2012 I don't understand your comment regarding relation between the new/old field wire and the ammeter. The ammeter is essentially a voltmeter but rather than connecting one end meter to ground you are measuring voltage drop over known /calibrated resistance (aka a shunt) which gives you a voltage deference between the battery output and the alternator output in normal conditions would be relative a small voltage. So on ammeter gauge it is labeled amps because of Ohm's law I=V/R (R= known resistance or shunt). According to the schematic that I am looking at, that is what I see. I can't say too much about the "old" field wire in your situation without knowing where the other end of the "old" field wire goes or was/ is connected to. I would make darn sure you know where the other end of the "old" field wire(s) go like ohm it out (continuity check) or remove it all together would be the best. The field circuit of the alternator is important part of the electrical charging system and you want to make sure it is functioning properly. Because you sure is heck don't want to have in-flight electrical fire and have no way shutting off alternator output and / or isolating the electrical system if by chance alternator overvoltages and /or smoke in the cockpit or some other malfunction occurs. But in I my particular case, the field wire comes from the Alternator goes through one set of the contacts of the mater switch (DPST) to the Zeftronics voltage regulator while the other set contacts on the Master switch provides ground for the power relay. So what "type" of voltage regulator you have determines how / where the field wire(s) are connected up. Enough of my ranting about the importance of field circuit on the alternator/generator. James '67M20C Quote Link to comment Share on other sites More sharing options...
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