Low volts light and ammeter discharging, quiet radios

jpower

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James
Well, I went flying this morning, though it wasn't before I had some excitement. Okay, not that much excitement.

I finished the preflight on our lovely (rental) 1980 172P, and we jumped in and started up with no issues, but then, when we were taxiing out, the low voltage light started to flicker a little bit, then went solid. I said "ughhh" and continued to runup, where I was hopeful that we might get more juice. Unfortunately the light didn't go out, and when I checked the ammeter, it was a needle-width or two over into discharge. I taxied back and swapped planes, and the guy behind the counter said they'd look into it.

Is this an alternator failure? I would have expected that there would be more discharge than one or two needle-widths if the ammeter had completely kicked the bucket, but then again, I've never had this happen, so I'm really not sure.

Also, the first time I flew that plane (last Friday), the radios were awfully quiet, and they seemed about the same on the radio check today. The intercom was totally normal and radio checks came back loud and clear on both 1 and 2, but even with the volume on the radio and my headset full up, the transmissions others made were pretty faint. I assume the two issues are unrelated, because I would think that transmitting would be the first thing to go because it's more power hungry, but nobody seemed to have any trouble hearing us then. What could cause that? Radios going bad?

Thoughts?
 
Well, I went flying this morning, though it wasn't before I had some excitement. Okay, not that much excitement.

I finished the preflight on our lovely (rental) 1980 172P, and we jumped in and started up with no issues, but then, when we were taxiing out, the low voltage light started to flicker a little bit, then went solid. I said "ughhh" and continued to runup, where I was hopeful that we might get more juice. Unfortunately the light didn't go out, and when I checked the ammeter, it was a needle-width or two over into discharge. I taxied back and swapped planes, and the guy behind the counter said they'd look into it.

Is this an alternator failure? I would have expected that there would be more discharge than one or two needle-widths if the ammeter had completely kicked the bucket, but then again, I've never had this happen, so I'm really not sure.

Also, the first time I flew that plane (last Friday), the radios were awfully quiet, and they seemed about the same on the radio check today. The intercom was totally normal and radio checks came back loud and clear on both 1 and 2, but even with the volume on the radio and my headset full up, the transmissions others made were pretty faint. I assume the two issues are unrelated, because I would think that transmitting would be the first thing to go because it's more power hungry, but nobody seemed to have any trouble hearing us then. What could cause that? Radios going bad?

Thoughts?

Check the volume knob on the audio panel. If it's turned down then it will effect overall volume level.
 
Could be a number of things. 172s it's usually the two aforementioned items.
 
At least you got to the runup area. A couple weeks ago I didn't even pull the 172 out of the hangar. ARROW, fine. Master switch on, lights on, pitot heat on, flaps down. Gas gauges read full. Quick walk around to check the lights and back to the cockpit. Gas gauges now read 1/2 and the electric gyro in the TC sounded distinctly slower than a moment before. Looks to me like a battery has quit. Shut off the master, called the maintenance officer for the plan, cancelled the reservation and found that the 182 in the next hangar was available. Reserved it and away we went. I'm not sure the engine would even have turned over in the 172 with the way that battery was going down.
 
Alternator brushes? Loose ground wire? Voltage regulator? Fan belt failure?

Any number of possibilities.
 
Alternator brushes? Loose ground wire? Voltage regulator? Fan belt failure?

Any number of possibilities.

Fan belt failure? Pretty certain a fan belt is not listed in the 172 parts list.
 
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Fan belt failure? Pretty certain a fan belt is not listed in the 172 parts list.

Sure, not a "fan belt" but the alternator belt on the club's 172 sure looks like the fan belt on a lot of older cars. Same construction, same idea. Just doesn't drive a water pump or fan.
 
Sure, not a "fan belt" but the alternator belt on the club's 172 sure looks like the fan belt on a lot of older cars. Same construction, same idea. Just doesn't drive a water pump or fan.
A few months back, my 182 had some voltage/charging issues... the problem turned out to be the belt was loose.
 
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