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Some A/F switch answers... Posted by walt [Email]  (#2707) [Profile/Gallery]
(more from walt) on Mon, 7 May 2012 06:25:56
In Reply to: a/c anti-frost switch questions, johnd, Sun, 6 May 2012 20:18:41 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Switch is removed by 13mm nut on backside of switch pictured below. Recommend taking out center console, knee interior trim piece, and plastic heater distribution piece in order to get to it. Adjustment screw is either a small phillips screw on outside, or small Torx 0.7x4 screw hidden underneath white cover. Torx screw location is shown by green arrow. After carefully (don't sharply bend wire) removing the sensor wire tip from evaporator fins, switch operation can be tested with a voltmeter using 0 to 200 ohm resistance function. Voltmeter leads are connected to male spade lugs coming from plastic part of switch. Should have continuity (approx. 1 ohm) at room temp. down to approx. 36 degF. If the sensing wire tip is placed in ice slush in a baggie, resistance will rapidly climb until it exceeds 200 ohms, and switch is open (this turns off compressor). After removing sensor wire tip from slush, wire will slowly warm and resistance will go back to 1 ohm turning compressor on again. If high resistance at room temp, then may be able to fix by turning adjustment screw while observing resistance. If never goes to zero ohms, then sensor wire may be kinked or fluid leaked out. If that's the case, it's time for new A/F assembly. From what I've read, bypassing the A/F switch is not recommended, because air doesn't flow well through a block of ice on evaporator fins. Also refrigerant is supposed to completely change back to gas on exiting evaporator, because liquids are not compressible by compressor and could damage it. The NG900 still has this analog A/F switch. However, the OG9-3 A/F switch uses a negative temperature coefficient (NTC) thermistor.
posted by 72.49.19...
, Mon, 7 May 2012 06:25:56 <-- Viewing This Message
, Mon, 7 May 2012 10:01:10, Tue, 8 May 2012 10:33:33
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