My electrical issues started last year in July, when my magneto packed up got overhauled and reinstalled.
More than once, when everything was on and the load was high it happened that during the flight my avionics would just switch off. I posted this a while back. The alternator light had a brief flicker and the volt indicator gauge also fell for a millisecond. The G2 screen also showed some flickering before the shut down would happen.
We pulled some CBs, switched off the pitot and the nav lights to shed some load which seemed to keep the electrical system happy.
I asked my shop to check the alternator and based on some ground checks they found it was ok. During my annual I sent the alternator to Röder for an overhaul and they found oil in it. their comment was that this should have been the culprit of my electrical problems. I took my aircraft flew to Colmar to shoot some approaches, refuelled, paid my taxes and at 5 I wanted to leave for Zurich. I pressed the battery switch but the whole system was just dead. Not a low battery, just dead not sign of life at all.
Left the airplan there as there was nobody there anymore and had the local mechanic check the battery. They found the battery relay would not engage, so they took it out and apparently cleaned it and put it in again. when I picked the aircraft up from Colmar the engine started with no problem but I had this rough magneto issue which we discussed in the high EGT thread.
After all that tribulation with the ignition finally sorted my friend to the plane for a first flight and immediately during take off, all radios switched off again. He recycled the main avionics switch, the radios came back momentarily but then switched off again. So he had to recycle again and then they stayed on for a while. He did some tough and goes and when he wanted to leave the airport again after having shut down the engine, all avionics came on eventhough the main avionics switch was off.
He had to jump start the engine again as on his last flight the battery would not come to life at all. I think the battery relay again is not engaging.
So here are a number of questions. if the battery relay is faulty could that mean that avionics are just hanging on the alternator and susceptible to unstable current and switch off because of this? Could the avionics relay be faulty? this should not be the avionics master switch. If you wiggle this switch nothing happens. What could be the cause for these avionics outs during take off and climb. It is usually more stable during cruise.
Any hint would be much appreciated.
Placido
Get all the grounds (earths) checked especially in the battery and relay areas, this looks like a classic grounding problem to me.
Grounded is the cheapest thing to check before you get into more complicated things.
Yes the big clue is the avionics being ON with the avionics master being OFF.
The TB20 wiring is airframe S/N dependent and some don’t even have such a switch, or have a switch but it isn’t the “proper type” which works in reverse i.e. switches a relay so if the switch fails the relay energises and the avionics come ON. The more recent system is shown here.
Assuming you have the “reversed system” then check around the switch and the wiring and grounding.
If the battery becomes disconnected you might get an unstable alternator output but the standard Lamar voltage regulator has an overvoltage trip which shuts down the field current and it doesn’t come back on until, AFAIK, you interrupt the field current with the FIELD CB.
I have additional info, the avionics always shut off when my friend activated the gear or the flaps. This increases the electrical load so I think it has to do with the battery not being online and serving as a buffer or the battery was so low that it couldn’t compensate.
What are your thoughts?
placido wrote:
This increases the electrical load so I think it has to do with the battery not being online and serving as a buffer or the battery was so low that it couldn’t compensate.
Hello neighbour,
different type but we had something very similar a few years ago: We lost all electrics when activating the old landing light. Turned out to be a bad voltage regulator on the alternator. That was the reason we changed to LED.
If I remember right one of the effects was that the battery did not charge as it was required to and therefore eventually the alternator field failed too. At least that is how it was explained to me at the time. So either not online or not delivering enough current to buffer sounds like something worth investigating yes.
Hi Mooney,
I am pretty sure it has something to do with a) the battery relay or b) the battery itself. I have found out over the years that shops have a really bad habit of using your battery when working on the plane and leaving it half empty. It could just be that the battery was nearly flat since they have worked on my plane so many times and when my friend took the plane for a flight it just did not have enough juice to buffer the spikes.
On the other hand, the fact the everything came on with the avionics switch being off is another mystery in itself.
the avionics always shut off when my friend activated the gear or the flaps
This should be reproducible on jacks. Then you can troubleshoot it easily.
A low battery is not uncommon during maintenance but the battery tops off within say 10 minutes of flight. The alternator puts something like 30-40 amps into it initially (depending on the battery and the alternator; a Concrode battery briefly draws 2x more current in this situation than a Gill). So if this is happening during flight after some time, it is either a duff battery or some wiring issue or perhaps a bad relay contact. What battery is it and how old is it? If it is a Gill, toss it out and put in a Concorde before any further work.
The avionics master issue is probably unrelated, but you never know. I wonder if @wigglyamp or @GarryIAE have seen this before?
My friend flew for over an hour and the battery didn’t charge, so I think the battery relay is also faulty. the battery is quite new maybe slightly more than a year or so.
When I got stuck in Colmar in March the shop there checked the battery and it was good. it was holding its load. It looks like they should have exchanged the battery relay and not just cleaned it. Maybe also the avionics relay is faulty?
looks like they should have exchanged the battery relay and not just cleaned it.
You cannot “clean the battery relay”. These are sealed Stancor relays and they have a “swaged” lid like this
which cannot be opened without destroying the whole thing. So I think somebody is pulling your leg when they said they cleaned the battery relay. However these relays are not expensive. From Socata with an EASA-1 (and possibly with the original label removed) they might be a few hundred € but are easily available from the usual US distis like mouser.com.
More details here and I think your plane is similar to mine except possibly it doesn’t have the ground power relay (whose purpose is to disconnect the battery when external power is connected) but I am not sure as the TBs went through variations of this over the decades. It’s a pity that European pilots appear to get little or no detailed support on the Socata owners’ group these days – I hear various complaints along those lines. However one can look up the wiring diagrams with a reasonable degree of reliability on the ATP CD, against the airframe S/N range which is at the bottom of each page.
checked the battery and it was good
I wonder if they did. There seems to be a thread running through this where stuff was done but actually wasn’t. The business is full of clueless people and Switzerland is sadly not better than anywhere else 
The problem is that if the battery relay is not closing, nothing much is going to work. Look in the link above and at the circuit diagram. The starter motor current flows through the ground power relay AND the battery relay AND the starter relay. If the battery relay was duff enough for the battery to not charge, the starter motor would not work. So if the battery is not charging, it is something else. Is the bus voltage right? 14V or 28V? What is the battery current meter showing after the engine starts, and in cruise? It should show an initial heavy draw (tens of amps) and eventually about 0.5-1.0A during cruise.
Firstly as Peter said you can’t clean a battery relay, it is a sealed unit.
The more I read above the more I am convinced that your problem involves a grounding problem, there seems to be little logic in what is happening and this has the look of an intermittent ground some place in the system.
Another thing that is worth looking at is the alternator belt tension.
