Page 17 - Volume 14 Number 8

King Air 90/100 drivers, I’ll catch you on the next one.
Belt and Quill Shaft
Troubleshooting is like peeling an onion layer by layer. The first layer is the belt and quill shaft – an easy check. Open the righthand engine aft inboard cowl. To do this you may need a screwdriver – model 200s have two camlocks on the bottom just forward of the front latch, these camlocks could require a common or Phillips screwdriver; 300s have three screws on the cowl door; 350s have latches only.
The compressor is right there so look for the belt. If the belt is shredded or missing, that’s the first thing to fix. The belt might be the only issue, or it could mean the compressor is frozen. If the belt is intact, try to move it back and forth. It should only move about one-fourth inch and the clanking noise you hear is normal. If the belt moves freely without clanking, the quill shaft has sheared and must be replaced. If the belt and quill shaft are good, then you must cut into the next layer of that onion.
N1 Low Light
In the cockpit, turn the environ- ment switch to “Auto” (you can do this without the engines running) and look for the green “Air Cond N1 Low” light on the annunciator panel. If you don’t see it, turn the envi- ronment switch to “Manual Cool” and look again for the N1 Low light. If you still don’t observe it, toggle the Increase/Decrease switch to the “Decrease” position for at least 90 seconds and look again for that N1 Low light. If you finally get the light at this stage it means you may have a temp sensor problem – the system thinks it is already cold enough, but the sweat dripping from your brow indicates otherwise. If you get the N1 Low light right off the bat in “Auto” or in “Manual Cool,” it means your AC problems are elsewhere and you must delve deeper still.
AUGUST 2020
Reset Switch – Nose Gear Wheel Well
Go to the AC reset switch in the nose wheel well on the left-hand side. A yellow light in the switch indicates the AC has tripped, so if you see the light you should press the switch to reset the AC system; the light should go out. If there is no light, press the reset switch anyway. Many times, the switch has tripped, but the bulb is burned out so you have no yellow light.
After pressing the reset switch, you need to get back in the cockpit, turn everything off and fire up the right-hand engine, bringing it up to approximately 64% N1. Once your load meter indication goes below 40%, turn the AC to “Auto” and keep your eye on that load meter. Within 7-15 seconds you should see a spike in the load meter telling you that the condenser blower just turned on. If you do not see a spike, turn the AC to “Manual Cool” and look again for
The N1 Low Light on the annunciator panel is helpful when troubleshooting air conditioning issues on your King Air.
a load meter spike after 7-15 seconds. If the AC will not turn on in “Auto” or “Manual,” then most likely one of the pressure switches is bad or there is no power going to the system’s printed circuit board (PCB).
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KING AIR MAGAZINE • 15