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- Sep 20, 2021
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On an Autocontoller III B head unit the two A/P switches (on/off and heading) are momentary switches. The top part of the rocker switch has a metal plate that is pulled towards the switch plunger by a small 3/4” diameter electromagnet thereby closing the circuit. On the INOP unit I am working to modify for my home cockpit, I found that two 9v batteries in series (18 volts) works to energize the magnets but 12 volts is not enough to do it. The aircraft battery system is 12 volts. So I assume the autopilot circuitry somehow steps up the voltage to activate those magnets. Does anyone know what voltage is supplied to those electromagnets in say a Piper PA28R Arrow II?
