Tommy Posted January 14, 2015 Report Share Posted January 14, 2015 Ok! My charging system trouble shooting continues. My A&P is still on holiday %@#$%. My bus voltage is at battery 11.8V. There is no field current to the alternator. So I swapped out the old VR (Electrodelta VR-415D) with Zeftronics R15300 (my unit is pretty old anyway), hoping it was the problem. But it wasn't. The TSL LED light didn't even flash at all when Master is on nor when both Master and Engine is running. So the problem is presumably upstream. So I need to measure 1) Point 1 - this is where the power is furnished to VR, how do you do this on a Cannon plug? 2) Alt field CB - easily accessible when glare shield is off, how do you measure if there is current flowing thru the CB? 3) Master/Alt switch - how to do measure if there is currently flowing thru the alternator switch? 4) all the wiring in the between those points... (this would be painful) Also I assume there is no separate OV (both VR-415D and R15300 has built in OV) in a 81 J? Thanks guys! I am so close yet so far... Not the first one and certainly won't be the last one to say " I hate electrical problems!"" Quote Link to comment Share on other sites More sharing options...
Mooneymite Posted January 14, 2015 Report Share Posted January 14, 2015 I presume the alternator itself checks out? If not, I'd suspect one of the diodes is bad. Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 14, 2015 Author Report Share Posted January 14, 2015 I think the alternator is ok - I assume so - since no field current is supplying the alternator... Quote Link to comment Share on other sites More sharing options...
N601RX Posted January 14, 2015 Report Share Posted January 14, 2015 You really don't want to measure current at the points mentioned above, just measure the voltage to ground. Start at the alternator and work backwards until you find the point where the voltage is present. Some regulators also have an enable and remote sense line. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted January 14, 2015 Report Share Posted January 14, 2015 Measuring current is always difficult, but measuring voltage should be sufficient. You can get to the master switch by crawling under the panel. If you remove the screws, I think you can loosen the whole circuit breaker panel and move it out enough to probe the individual breakers, if not, then remove the panel nut from the breaker and try to push the one breaker back so you can access it. You can also loosen the tach and the manifold pressure gauges and push therm back to get at the breakers. The cannon plugs can be probed with your meter probe (ok here we go) if your probe is too big to go into the female then use an unbent paper clip to probe the female. 1 Quote Link to comment Share on other sites More sharing options...
1964-M20E Posted January 14, 2015 Report Share Posted January 14, 2015 Ouch!! A paper clip into the female part. However, a paperclip is a paperclip and if it is unbent then it is still paperclip. You have to bend the wire of the paperclip to straighten it out then you can used it. Just messing with you. That is an excellent way to get a reading from a receptacle. Just don't try this at home. 1 Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 14, 2015 Author Report Share Posted January 14, 2015 Where do I need to put the red and black probes of a multimeter in order to get voltages readings across 1) master/alt switch 2) canon plug 3) alt field CB 4) other points? Ah the paper clip sized probe! Always a favourite with the ladies... Quote Link to comment Share on other sites More sharing options...
N601RX Posted January 14, 2015 Report Share Posted January 14, 2015 The black goes to the airframe. With the red lead prob each side of the switch, breaker ect to make sure you have voltage coming to it and and leaving. 1 Quote Link to comment Share on other sites More sharing options...
Andy95W Posted January 14, 2015 Report Share Posted January 14, 2015 I've replaced or repaired more field wires than voltage regulators or alternators on customers' airplanes. They live a pretty hard life with heat, vibration, flexing, etc. 1 Quote Link to comment Share on other sites More sharing options...
Yetti Posted January 14, 2015 Report Share Posted January 14, 2015 The proper sized nail is also a good probe. Also alligator clip the VOM ground to a good ground. Then you just have to work with the positive lead of the VOM A set of these will keep you from arcing stuff Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 15, 2015 Author Report Share Posted January 15, 2015 Ok more test done. 1) no power is furnished thru Wire A (wire 1) to the VR. 2) alt field CB is furnishing power power in and out when master is 3) Is it possible that the master/ alt switch is the problem - only if it's downstream of alt field CB (ie. between VR and Alt field CB) ? How do you test the master /alt switch? Thanks guys Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 15, 2015 Author Report Share Posted January 15, 2015 Which terminal should I put my volt meters on to see if there is power furnishing to the VR? See attached The top right hand corner connector's wire loops back to the switch itself (?ground) Thanks guys Quote Link to comment Share on other sites More sharing options...
Guest Posted January 15, 2015 Report Share Posted January 15, 2015 If the top right wire as viewed in the picture goes to ground the bottom left should be coming from the master relay coil, closing the master switch closes the master relay. The other two wires are alternator field, one coming from the alternator field circuit breaker, the other powers the voltage regulator. You can bypass the switch by making a small jumper with two 1/4" male spade ends, push them into the two female spades and then check for proper voltage at the alternator field terminal. Many times the contacts in the master/ alternator switch become arced causing a high resistance in the circuit, bypassing the switch proves or disproves the theory. Clarence Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 15, 2015 Report Share Posted January 15, 2015 Tommy, (Clarence not only types faster than me, but he is qualified for this type of info...!) Since I typed it, I'm giving it out anyway..... If you have a multi-meter. It can measure volts, resistance, and amps. It looks like you want to know if your switch is working. You are trying to measure resistance across the switch to see if it is working... You have all the wires off... Measure the resistance from one post to the next... (I expect top post to bottom post) The switch is probably really two switches in one (double pole double throw). On/off X 2 Then flip the switch... Measure the resistance again. If the switch is working, the resistance is very low (near zero) when the switch is on or 'closed'. If the switch is off 'open', the resistance is very high (infinity) Your main switch (usually red) works in a similar way. If you leave the wires on you test it by measuring volts... If you take the wires off, use resistance... One probe on the switch post, one to the steel cage for ground. Using your eyes... You can see that the other switches are all attached to a brass bar. This is called a bus. The bus gets it's power from the battery. Some additional complexity in this system is caused by what these main switches may be connected to. The switch activates a solenoid which is the actual switch for the circuit. Your wiring diagram has all the details of how many solenoids you have and what wire goes where. Solenoids are known to oxidize and wear out. Fortunately they are easy to swap out. Your POH has your electrical diagram. If this description has been helpful for you... Consider leaving this type of work for your professional mechanic. Removing wires from your main switch when you don't need to can lead to trouble later on while flying. Consider the following... (1) If your main power switch is working... Turn it on. If you hear a click coming from near the battery, that is the solenoid coming on. (2) Check the voltage either at the instrument panel or by using your multimeter, set to volts. Use the cigarette socket with the two probes. One at the bottom and the other at the inside side of the socket... (13+V is good) There are a few methods of measuring volts. - Your JPI has a volt meter in it. - Your instrument panel has a volt meter in it. - your portable Garmin has a voltmeter in it. (3) start your engine... You should get an instrument panel light indicating voltage warning. The alternator isn't on yet. (4) Measure your volts again. (Any number above 12 is normal). You know without turning the alternator on, the voltage will only go down from here... (5) turn on the alternator switch. (Did the warning light go out?) (6) it may take a certain engine rpm to get the generator to produce enough energy to make the light go out. Typical for my bird, this is a fast taxi.... (7) when I had a similar challenge, I suspected the wire that went from the voltage controller to the generator (65C). I ran an extra wire from the post on the generator's field to the cockpit. I was able to measure exactly what the controller was not doing using my volt meter, and bought myself a Zeftronics device. (8) the faulty worn generator ruined my voltage controller... Look around the battery area there are probably three or so solenoids. Each one will click loudly when they are activated. When they are on, measure the voltage across them like you would do a switch. When they are off the voltage will be high. When they are on the voltage drop should be near zero. If there is a few volts drop across a solenoid when it is on, this is an indication of a worn or dirty part. Remember you are working with some high voltage. It can hurt or destroy your parts. Be careful. Hope that helps... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 15, 2015 Author Report Share Posted January 15, 2015 Hi Clarence, just to confirm that I can actually connect spades of alt field CB wire to VR wire and see if there is any power goes to the alternator and if it has then the switch is defective? Thanks Quote Link to comment Share on other sites More sharing options...
Guest Posted January 15, 2015 Report Share Posted January 15, 2015 Hi Clarence, just to confirm that I can actually connect spades of alt field CB wire to VR wire and see if there is any power goes to the alternator and if it has then the switch is defective? Thanks Yes, connecting the wires together will bypass the switch. If you then get power to the alternator field terminal you will have proven the switch is the trouble. If the alternator field becomes energized, the core and pulley will be magnetized, proving the circuit is good. To test the alternator you can "Full field" the alternator. Pull the alternator field circuit breaker. Install a jumper wire from the alternator output terminal( larger stud) to the alternator field input terminal( smaller stud) you will now be feeding battery voltage directly the the field windings. Connect your multi meter to the aircraft buss, unless your plane has a volt meter and an ammeter. Start the plane at very low idle RPM, note the two meters. Increasing RPM slowly should increase output voltage and output current, proving the alternator works. USE CAUTION THERE IS NOW NO REGULATOR IN THE CIRCUIT, OTHER THAN YOUR GOOD COMMON SENSE. DO NOT TURN ON ANYTHING, NO AVIONICS NO LIGHTS ETC. Clarence Quote Link to comment Share on other sites More sharing options...
Tommy Posted January 16, 2015 Author Report Share Posted January 16, 2015 I GOT IT FIXED!! My A&P returned from his holiday today and we went straight to work. Like all other mechanics, he was pretty convinced that it is the alternator that's playing up! I showed him otherwise in less than 30 seconds. I then explained in details all the tests that I have done so far. He was duly impressed by it! Thanks guys! Using Clarence's method, we quickly identified that the connector at the alt CB field is bad (thank goodness that the wire is good!) and after replacing it: Voila! Power to my new Zeftronics VR! And the whole charging system is working again! 14.2V on my EDM JPI! All under an hour! For those who helped me, thank you!! For those who doubted me and questioned me, thank you as well but honestly, I can tell you that for one I didn't do anything illegal and I didn't break anything (thank goodness). Not only I saved at least 6 hours of extra diagnosing and fixing work (which I used to buy a brand new VR and 4 fine wire Tempest plugs), most importantly, I GAINED some valuable knowledge on my aircraft system! I could've given the key and a blank cheque to my A&P but, to me, that's not what aircraft ownership is about... 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 16, 2015 Report Share Posted January 16, 2015 You have also gotten to know your good mechanic a little better. He knows your skill of diagnosing a problem a bit better. Sounds like a MooneySpace success story to me! Send some pictures... If they end up upside down, it's not your fault. It's something in our software.... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted January 16, 2015 Report Share Posted January 16, 2015 Tommy, Glad to hear you've cured the troubles! Clarence Quote Link to comment Share on other sites More sharing options...
1964-M20E Posted January 16, 2015 Report Share Posted January 16, 2015 Tommy Excellent job. It appears that you are breaking in your mechanic quite well. This will go a long way to a good relationship with your mechanic and your plane and saving you money. Unfortunately It appears I may be losing my mechanic sometime this year and I will have to find a new one and break him in. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted September 18, 2020 Report Share Posted September 18, 2020 On 1/15/2015 at 10:08 PM, Tommy said: I GOT IT FIXED!! My A&P returned from his holiday today and we went straight to work. Like all other mechanics, he was pretty convinced that it is the alternator that's playing up! I showed him otherwise in less than 30 seconds. I then explained in details all the tests that I have done so far. He was duly impressed by it! Thanks guys! Using Clarence's method, we quickly identified that the connector at the alt CB field is bad (thank goodness that the wire is good!) and after replacing it: Voila! Power to my new Zeftronics VR! And the whole charging system is working again! 14.2V on my EDM JPI! All under an hour! For those who helped me, thank you!! For those who doubted me and questioned me, thank you as well but honestly, I can tell you that for one I didn't do anything illegal and I didn't break anything (thank goodness). Not only I saved at least 6 hours of extra diagnosing and fixing work (which I used to buy a brand new VR and 4 fine wire Tempest plugs), most importantly, I GAINED some valuable knowledge on my aircraft system! I could've given the key and a blank cheque to my A&P but, to me, that's not what aircraft ownership is about... When you found the issue, was it a connection inside the cannon plug? Quote Link to comment Share on other sites More sharing options...
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