View Full Version : Iffy electrics??
Ringway Flyer
7th Jun 2003, 19:36
Following my last posting when the alternator died, both alternator and the battery have been replaced. So far so good. Last w/e we flew for two sessions, each lasting about an hour. On arrival back at EGCC, I switched everything off, just leaving the alternator to charge the battery. I expected a charge rate of maybe 5 amps, but it was still pushing out 18 to 20 at about 1,800 rpm. Have we still got a problem? Wouldn't the battery be pretty well charged after a couple of hours running? Only things in use were strobes, transponder and the radios. Any ideas, please? (Next bit to be replaced will be the regulator....
Is your ammeter in the battery circuit, or in the alternator output? Could be either.
Strobes are probably an amp or so; transponder is a big user; radios use a few amps.
If the ammeter is in the alternator output, 20 amps isn't beyond credibility.
bluskis
8th Jun 2003, 06:04
If you replaced the battery it should have been charged to start with.
Is it possible that you have a fault in the regulator which is screwing both your alternator and battery?
If alternators don't have regulators, they certainly have current limiters which could be at fault.
Alternators have regulators, but they can be internal.
You need to know where the ammeter is fitted in the circuit. The POH will normally include a wiring diagram that makes it clear. If the ammeter is in the alternator output (usual for Pipers) then you'd need to switch off everything to see what current is being pumped into the battery.
If the battery is in reach from inside the cockpit, feel it after a longish flight to see if it is hot. It shouldn't be. Hot = being overcharged.
The ammeter in our Arrow is so inaccurate it tells you little more than "not a lot", "normal-ish" and "lots". We know the normal in-flgiht position of the needle (once the alternator has replaced the power used to start the engine).
mad_jock
8th Jun 2003, 09:29
The strobe systems uses hellish amounts of juice.
I was taking a look at one and couldn't find a DC power supply beafy enough to power it. (over 15 amps).
Turn everything off and see what happens.
From the readings you mention 18amps dosn't seem to bad .
Check the voltage on the DC bus should be +14. if it is +14 the reg is fine.
Bat shouldn't be an issue during flight or with the engine running because all it does is except charge so if the DC bus is +14 everything is OK. It only comes into play when the alt voltage drops below 12V.
These electrical probs are a complete pain and most airframe and engine boys are in as much in the dark as the customer
MJ
Ringway Flyer
8th Jun 2003, 22:48
Thanks for the comments so far. It's an Archer III, with a digital readout type ammeter, which measures alternator output - so in flight it's usually around 15 amps. It's a 24volt system and there is no obvious way to monitor the battery voltage from the cockpit. I intend to check the battery voltage before we fly next time, and also when we return. I suspect the regulator (in this case a separate unit on the engine side of the firewall), but I guess it could be bad connection somewhere, a badly done crimp, for eg. The check last time was done with everything off, and the engine speed set to give the highest reading on the ammeter....