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Battery Leak Dynon AP 74 Autopilot Servo CB

T

Tcheairs

Well Known Member
Been having trouble keeping my battery charged (master battery switch off and avionics switch off) and in fact ruined an Odyssey PC 680, Finally got around to hooking up the multimeter and confirmed the leak today in mm amps. Found a 07.91 leak in the mili amp mode. Pulled all cbs and determined the leak is on the Dynon AP 74 autopilot servo cb. All the other cbs checked... no leaks.

Haven't figured out how to add photos to this forum,but here's a link to my Google Drive photo which is the best that i can do. Guess I'm reading 07.91ml leak.

https://drive.google.com/file/d/1eHu4QcrPY9mj-OMu2u-ImAkZChdnR33v/view?usp=sharing

Any ideas as to how to best troubleshoot will be appreciated.
 
Looking at your photo I’m not sure what you measured - but it was not a parasitic load on the PC-680.

I suggest:
- Disconnect the battery positive lead.
- Connect the battery ground to the firewall.
- Put your mAmp meeting between the battery positive terminal and the battery positive lead and see what you have.

Carl
 
Autopilot connection point

I'm not sure if I understand what the meter is reading, but the autopilot sub-system should not be drawing any current if the master solenoid is off. If it is drawing current then it has possibly been wired up incorrectly and is bypassing the solenoid. I would start by tracing how the autopilot CB and power circuit is connected to the battery. Do you have a wiring diagram for the plane?
 
Carl Froehlich said:
Looking at your photo I’m not sure what you measured - but it was not a parasitic load on the PC-680.

I suggest:
- Disconnect the battery positive lead.
- Connect the battery ground to the firewall.
- Put your mAmp meeting between the battery positive terminal and the battery positive lead and see what you have.

Carl
Click to expand...

If you do this then use the A setting first before selecting the mA range.

Another way to trouble shoot is to disconnect the leads from the battery (assuming there is only one battery in the plane and no back up battery). Then measure resistance between the leads (not the battery terminals!) with the master turned off. The resistance should be infinite. If it is not then turn off circuits and pull CBs and remove fuses until you find where there is a connected circuit.
 
Tcheairs said:
Been having trouble keeping my battery charged (master battery switch off and avionics switch off) and in fact ruined an Odyssey PC 680, Finally got around to hooking up the multimeter and confirmed the leak today in mm amps. Found a 07.91 leak in the mili amp mode. Pulled all cbs and determined the leak is on the Dynon AP 74 autopilot servo cb. All the other cbs checked... no leaks.

Haven't figured out how to add photos to this forum,but here's a link to my Google Drive photo which is the best that i can do. Guess I'm reading 07.91ml leak.

https://drive.google.com/file/d/1eHu4QcrPY9mj-OMu2u-ImAkZChdnR33v/view?usp=sharing

Any ideas as to how to best troubleshoot will be appreciated.
Click to expand...

How is power getting to the AP CB if the master contactor is open?? If that CB input goes straight to the battery, might be wise to wire it like the others, through the master contactor.

Larry
 
I'm thinking it's more likely that the master has the "leak" here, and not one of the downstream circuits. The master should be a hard cutoff - with NOTHING getting past it - but sometimes they do develop small "leaks" as you call it due to metallic powder coating the inside and allowing some stray current to get past.

The master switch should be the ultimate "Thou Shall Not Pass!" of the battery. Nothing gets wired between it and the battery.

If any power is present at all downstream of the master, it will find a through the myriad of circuits that most of us have somewhere, even in some small quantity, as you've seen with the one circuit you found. The master is there is shut ALL of that off - completely. If your master is not doing that, then you need to replace the master switch, not go chase gremlins elsewhere.
 
I don't mean to be argumentative here...just a question..If the master battery shutoff is leaking, shouldn't I be able to see current leak on multiple or at least several of my 20 something DC circuits, rather than just the one autopilot circuit?
 
Tcheairs said:
I don't mean to be argumentative here...just a question..If the master battery shutoff is leaking, shouldn't I be able to see current leak on multiple or at least several of my 20 something DC circuits, rather than just the one autopilot circuit?
Click to expand...

In theory, yes, which is why I suggested that the AP CB might have bypassed the master contactor. You should see current on many of your CB's if the master was leaking current.

Larry
 
Larry, I was referring to the post just above yours..By Airguy..I agree with you that the autopilot must be "hard wired" somewhere bypassing the master battery switch

I'm thinking it's more likely that the master has the "leak" here, and not one of the downstream circuits. The master should be a hard cutoff - with NOTHING getting past it - but sometimes they do develop small "leaks" as you call it due to metallic powder coating the inside and allowing some stray current to get past.

The master switch should be the ultimate "Thou Shall Not Pass!" of the battery. Nothing gets wired between it and the battery.

If any power is present at all downstream of the master, it will find a through the myriad of circuits that most of us have somewhere, even in some small quantity, as you've seen with the one circuit you found. The master is there is shut ALL of that off - completely. If your master is not doing that, then you need to replace the master switch, not go chase gremlins elsewhere.
 
If you've got something wired for power between the master switch and the battery, that would explain what you are seeing. It should not be wired that way, but it wouldn't be the first time I saw it...
 
Carl Froehlich said:
Looking at your photo I’m not sure what you measured - but it was not a parasitic load on the PC-680.

I suggest:
Disconnec the battery NEGATIVE lead first.
- Disconnect the battery positive lead.
- Connect the battery ground to the firewall.
- Put your mAmp meeting between the battery positive terminal and the battery positive lead and see what you have.

Carl
Click to expand...

Just in case that wasn't clear. You should never be messing around with the hot side connections without first disconnecting the negative. Bad things can happen.
 
Raise my hand

airguy said:
If you've got something wired for power between the master switch and the battery, that would explain what you are seeing. It should not be wired that way, but it wouldn't be the first time I saw it...
Click to expand...

Well I do. I have a cabin light on a switch wired direct to battery. That way I can turn the light on at night without flicking on the master. But is on fusible links and is very low draw so if left on doesnt drain battery.
 
airguy said:
Well, that's one way to accomplish that - not necessarily the best way.

Yeah I get it, but...
Click to expand...

Would you please show me the correct way to connect my LSI ignition and EBuss
so I have the needed power with the master off during an emergency.

Thanks.
 
gasman said:
Would you please show me the correct way to connect my LSI ignition and EBuss
so I have the needed power with the master off during an emergency.

Thanks.
Click to expand...

Don't be pedantic. You know quite well what was meant.
 
airguy said:
I'm thinking it's more likely that the master has the "leak" here, and not one of the downstream circuits. The master should be a hard cutoff - with NOTHING getting past it - but sometimes they do develop small "leaks" as you call it due to metallic powder coating the inside and allowing some stray current to get past.

The master switch should be the ultimate "Thou Shall Not Pass!" of the battery. Nothing gets wired between it and the battery.

If any power is present at all downstream of the master, it will find a through the myriad of circuits that most of us have somewhere, even in some small quantity, as you've seen with the one circuit you found. The master is there is shut ALL of that off - completely. If your master is not doing that, then you need to replace the master switch, not go chase gremlins elsewhere.
Click to expand...

I apologize Greg, I guess I misunderstood your statement.
 
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