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C-180 Intermittent weird master switch power problem

When you change out any system like that, ALWAYS remove the old wiring. If it's still hot, it's a safety issue. Even if it's not, it's still 'stuff' that you don't need/want/use that you are carrying in the aircraft.

Just to give you an idea of the weight of wiring; I once rewired an entire Bell 212, from nose to tail rotor. We removed the connectors and clamps from the old wiring and found that we had 158 lbs of wire.

Web
 
Probably time to remove that old battery and cables and install an Odyssey on the firewall. Attach a new solenoid right to the battery box and make new, very short cables. Enjoy much better battery performance and the typical 17# of weight savings.
 
I understand you folks operating in the below zero temperatures wanting batteries close to the engine, but for the life of me I don't understand why you are so insistent on moving your CG forward on an airplane which is normally nose heavy.

I can feel the CG shift in my 185 just by removing the back seat. It flies better with the seat in place.
 
Odyssey batteries perform far better than conventional batteries in the cold regardless of where you put them. The best reason to move it forward is SHORT cables. Smaller loss allows smaller battery. Smaller is lighter. Lighter is better in airplanes. I have battery and hydraulic tank on the firewall with big engine and big prop. No empty CG issues. My CG is 38.77 inches when empty on 29" Bushwheels, 33.20 on Fluidyne 3600s retracted. If I had to design an empty weight CG for a Skywagon it'd be hard to beat what I have. Very versatile, very useful.

Here's a snapshot of a normal flight CG. The battery up front is good.
 

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I'm pleased that it works well for you Stewart. If you were on floats or more so on amphib floats you would have a different point of view. I keep the battery in the back and carry a minimum of a half a case of oil there as well. The performance improvement is obvious at both ends of the operational speed range. Lightly loaded it breaks water indicating 37 knots and cruises indicating 122 knots at gross.
 
Another perk from moving the battery forward is that in cold weather it gets preheated when the engine does.

I like a 40 pound tool bag at the back of the extended baggage compartment. No question the airplane flies better with it than without. I will put money on that.
 
When I had the airplane apart doing the firewall battery install my wife came through the hangar and asked what I was doing. I explained and her immediate response was "cool, now I can bring more stuff." I've never had a problem with fwd cg when loaded.
 
Dave Calkins said:
I like a 40 pound tool bag at the back of the extended baggage compartment. No question the airplane flies better with it than without. I will put money on that.
Click to expand...

Absolutely! It's never occurred to me to fly my airplane without a tool bag, tire pump, tie down ropes, cargo net, spare oil, and his and hers rain gear in the aft baggage, and that stuff stays in the plane independent of my survival gear and day pack. Every Cessna I've flown flies better with the CG a little aft but that's not reason to balance the empty CG aft.

I often think about how guys load and fly, and why. For instance, STOL contests are flown with empty planes low on fuel. That's not how guys I know normally operate, including many of the contest pilots. As I build my current Cub I'm trying to get the empty CG forward to retain the ability to utilize the useful load capacity, which will shift the CG aft. I'm more concerned with balance than weight (within reason).
 
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So back to the electrical issue, it was deemed that master solenoid number 2 had also failed, and a "better quality" one replaced it. I've been under the wx myself so have not had a chance to flight check it. All the other concerns brought up on the thread here were followed up on and thanks again. Hopefully I won't be back here posting again on it in a month!

sj
 
So, the saga continues. Our master solenoid just went out again on the C180. This is the fourth one in two years. The mechanic blames poor solenoid quality but I keep wondering if there is something more? It is the contacts that are burning up, the solenoid keeps working... ideas? insights?

Thanks

sj
 
SJ said:
So, the saga continues. Our master solenoid just went out again on the C180. This is the fourth one in two years. The mechanic blames poor solenoid quality but I keep wondering if there is something more? It is the contacts that are burning up, the solenoid keeps working... ideas? insights?

Thanks

sj
Click to expand...

cut it open(take top off) post picture
 
SJ said:
So, the saga continues. Our master solenoid just went out again on the C180. This is the fourth one in two years. The mechanic blames poor solenoid quality but I keep wondering if there is something more? It is the contacts that are burning up, the solenoid keeps working... ideas? insights?

Thanks

sj
Click to expand...

master SWITCH is probably bad, and not holding solenoid fully on always... or bad ground for master SWITCH.... allowing it to open some and burn
 
SJ said:
So, the saga continues. Our master solenoid just went out again on the C180. This is the fourth one in two years. The mechanic blames poor solenoid quality but I keep wondering if there is something more? It is the contacts that are burning up, the solenoid keeps working... ideas? insights?

Thanks

sj
Click to expand...

could be wire corrosion too...heating up.....

run a new wires for master SWITCH also

also could be loose slide on connector at master switch(solenoid side), you can crimp them some to tighten
 
Points burn up from surface contamination. If they are clean they will chatter all day long and not burn. Either something is entering the solenoid or it is in there when manufactured.
 
An inductive load somewhere, supplied by the master relay, that remains connected when the master is engaged / disengaged? If so, could cause arcing with each on/off cycle.
 
1. If the master was intermittent, I would think all of my instruments and radios would flash on and off a lot - at least it would be noticeable - am I wrong?

2. There is no diode

3. The last two that failed were skytec - one of them in about a month. This one is also mfg. in China, but I can't remember the model.

4. We cut the last one open - it had burned up contacts - I will let you know on this one.

Thanks folks!

sj
 
The points are burning when the solenoid is opening/closing. That is when the arcing occurs. I agree that if it was chattering during operation you would see flickering lights/radios/gauges. The diode protects other connected equipment, not the relay itself. Are you positive that it is a master solenoid and not a start solenoid? Four post or three? What type of master switch are you using? Age of the switch?

Web
 
SJ said:
1. If the master was intermittent, I would think all of my instruments and radios would flash on and off a lot - at least it would be noticeable - am I wrong?

Thanks folks!

sj
Click to expand...

the small coil has to over come, and continue to overcome the spring pressure.... and it isn't

it wouldn't chatter, plunger would just not be a solid connection with the big posts, like when first powered up.... we run into this with bad start SWITCHES not making solenoid pull in solid, that why you alway jump past switch at solenoid when checking a slow cranking engine as a first troubleshooting step... found many...

(I have not reread all the old posts yet....)
 
Just a thought. If you have a bad connection or crimp at the battery, either ground or hot side, you could get a low voltage drop out situation.

Explanation: The master solenoid is hot all the time and switched to ground through the master switch. When the solenoid is closed, only a few amps of current ever flow through it, rarely more than 10 to 15 amps. At that level of current a one volt voltage drop at a bad battery cable crimp wouldn't be noticeable. If resistance = volts / amps, then the resistance is 1 volt divided by, say, 15 amps or .066 ohms. BUT, when you are cranking the starter motor the current flow will go up to 100 amps or more. During start up, that means that the voltage drop at that bad crimp will be, volts = amps x ohms, or 100 x .066 = 6.6 volts. That's the voltage drop JUST at the bad crimp. That means that your 12 volts from the battery, minus 6.6 volts at the bad crimp leaves you with 5.4 volts at the starter. If this happens, the solenoid will lose the voltage/amps at it's coil (remember that its wired hot to battery) and release. The moment the contacts break connection, the voltage is back to 12 volts and the solenoid immediately tries to close. This is what can cause the chatter. And if it only happens when your cranking the starter, you won't hear it or notice it.

If you think this is to extreme to be plausible, do the math with a half volt drop at a bad crimp. This means that you would still have a 3.3 volt drop just at the bad connection, leaving 8.7 volts at the starter. Still well below the 'danger zone' for drop out.

With all the trouble you've had, I'd recommend new ground cable, and new battery positive cables from the battery to the master solenoid terminal (inside and outside of the battery box).

Web
 
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