Yeah, well, they gave me a bill for $2300 and I bargained it down to $1500. And they lost a bunch of my cowl washers and panel screws just for kicks. That's now over $3000 on this with no solution. They had my credit card info--wouldn't start the work without it as a guarantee of payment--so there was no way I could not pay them.
Then, I thought of something awful. What if this really IS NOT A NEW PROBLEM AT ALL?
This 2nd alternator/air conditioning system was KNOWN to have a glitch in that it failed, kicked off line, at takeoff power. Carl Gull demonstrated this and told me about it the very first time I flew the plane, with him sitting in the right seat. Said CAC had not figured it out. Tom Coury posted above about this being the voltage regulator "doing what it is supposed to do."
Thing was, after the upgrade, it wasn't just happening at takeoff power, it was happening at cruise settings, right down to around 2000 rpm.
Now, I am a brain surgeon, not a rocket scientist, and maybe my Physics 101 understanding of this is flawed, but Jim put in an engine that produces greater torque, right? So what if I have been entirely off base by thinking about the problem as being rpm-related? What if it is power-related? With greater torque, I am producing the same power at a lower rpm than before. Power = torque x rotational speed. With an increase in power from 260 to 320 horsepower, about 20%, that means that the power output I formerly saw at 2600 rpm will now occur at around 2100 rpm, which is just about exactly where I see the problem start to occur. Easy enough to test--if I leave the prop at max rpm and simply throttle back, it should solve the problem if I am right about this. Will check that tomorrow but I bet I know the answer.
Please tell me I am wrong, because if this thinking is correct I have spent $3000 chasing a "new" problem that was not new at all, just the same old CAC known issue showing up in a different setting!
Anyway, to take it a step further then, there is something about the system that fails at high load (compressor) and high engine power. Could we simply be dealing with a voltage regulator that is not capable of handling that situation? In other words, with the engine delivering higher power to the alternator, the voltage change caused by bringing the compressor on line above a certain alternator output exceeds the limits of the VR, which then fails? Could we solve this with a different voltage regulator?
Moreover, if this is in fact the same problem Commander had all along with this system, it is going to show up in EVERY plane in which Jim does the upgrade in this context. The system as it was designed has an alternator but no battery, which I understand is not a great idea, and in fact temporarily adding a battery in eliminated it (but a permanent one requires STC or field approval, and a way of isolating this battery from the other one). Jim is thinking of an STC to fix the system by putting in a battery, but could changing the specs of the voltage regulator solve it?
Jeff Schweitzer
N115CE