AlbertF Posted October 12, 2019 Report Posted October 12, 2019 Hi folks. Just bought a 1974 M20F. Love it after only 10 hours of flight, but I have noticed something unusual with the battery charging system. Every once in a while the battery alert comes on in the jpi 700 and the auto pilot turns off due to insufficient charge. Concord battery is 2 years old. Checks out at 13.07 volts standing charge. Jpi 700 shows between 13.4 - 13.6 charging in flight, now that I’m watching it. I’m assuming my alternator is going out since I think I should see 14+ volts, but I don’t know whats normal. Thoughts? Quote
Janat83 Posted October 12, 2019 Report Posted October 12, 2019 Do you have voltage regulator, looks to me that your alternator is good, check your voltage regulator output, there must be a way to adjust the voltage regulator output, happened to me last year with similar symptoms and it turned out to be voltage regulator. Quote
Ragsf15e Posted October 13, 2019 Report Posted October 13, 2019 Here we go again... I just went through this with my 68F. Well, the low charging part. I never had any avionics drop off. Heres the deal, don’t go replacing stuff until you go through the electrical system with that voltmeter and figure out what is broken. I replaced an alternator, and voltage reg before doing my own troubleshooting and fixing it with a $20 circuit breaker that was building up resistance and lowering the voltage to the VR. Besides the CB feeding bus voltage to the VR, the field wire comes off the VR and goes back to your master switch before going to the alternator. That master switch can be a source of resistance. Never mind 50 year old wiring. Zeftronics has a nice troubleshooting guide on their website. 1 Quote
Ragsf15e Posted October 13, 2019 Report Posted October 13, 2019 Here’s the link to the last low voltage thread. Lots of good advice. Quote
corn_flake Posted October 13, 2019 Report Posted October 13, 2019 Is the engine running when you took that measurement? If yes, something is not right. If no, I 13.07v is the normal resting voltage immediately after shutdown for a gel cell battery. Resting voltage after 6 to 12 hours should be around 12.8v to 12.9v for a new battery. It is likely your problem is else where. Bad ground to lose positive wire to to the auto pilot. Quote
carusoam Posted October 13, 2019 Report Posted October 13, 2019 welcome aboard, Albert. It may help to include what autopilot is installed in the plane... But, better than that... The JPI700 is capable of collecting and storing data... Download the data, post it to savvy.com then share the link here... Your battery is showing that it is charged. you are describing voltage dropping out in flight. Your JPI has the data... It is in your hands to do something with that data... See if we can get to the next level, before money gets spent on the wrong areas...? +1 on Rag’s observation... PP thoughts only, not a mechanic... Best regards, -a- Quote
Yetti Posted October 13, 2019 Report Posted October 13, 2019 (edited) Stat with the wires at the alternator. consider replacing wiring harness or just redoing all the connections. It's a pretty brutal environment up there under the engine. Proper routing and strain relief of the wires. One of your crimp connectors may be just hanging on by a strand. Edited October 13, 2019 by Yetti Quote
Yetti Posted October 13, 2019 Report Posted October 13, 2019 (edited) And clean up the rats nest of wires back there by the battery. The wires that look like they are for a battery charger should not go into the battery box. Terminate them to the frame for the ground. and over on the hot side of the Master Solenoid on the back side of the battery box. The solenoid on top of the battery box is for shore power. The top pin in the three pin connector is what energizes it. Edited October 13, 2019 by Yetti Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.