I’m in the middle of upgrading the AC system in my 68 base Cougar. I was bench testing the fan control in the car and noticed with no vacuum source or blower box connected, the compressor clutch would engage any time the fan control switch was on. I haven’t looked at the schematic yet, but I’d expect the compressor clutch would only engage in AC mode. I assume there are downstream components that will open the circuit to the clutch so it doesn’t run in heat mode?
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Defrost mode, too.
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It uses the icing switch to determine if it needs to operate but often it works when the Outside temperatures are cold. When I used my Cougar as daily transportation I would unplug the compressor during the winter.
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In addition to the icing switch, there was the AC mode switch on the center duct air damper that only allowed the AC compressor to run when the damper was set for air distribution through the center AC ducts.
In 69-70, this switch was replaced by a micro switch that was operated by a cam on the controls when the lever was moved to select AC modes.
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Thanks for the replies on this. I’m not actually sure I have a problem yet, just trying to get ahead of it with checks along the way since I have it all pulled apart now and can access easily. My AC switch is intact on the air distribution box. As discussed above it acts as a circuit breaker to stop the compressor from coming on during cold temps? Additional to that there is also a sealed circuit breaker somewhere that I haven’t seen yet but it’s in the schematic. I have them both highlighted.
The icing switch that Royce described is the A/C Thermostat switch near the top. It turns off the compressor as needed to keep the evaporator coils from icing up. The A/C mode switch that I described is the A/C Control Switch you have highlighted in yellow. It keeps the compressor from turning on until the air damper directs air out the middle dash duct for A/C. Both of these switches and the circuit breaker (also highlighted in yellow) all have to be closed in order for the compressor to turn on.
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Yes, but my observation is the clutch comes on all the time. None of those components above are actually in the circuit yet. The plenum is rebuilt and bolted up just not hooked up. The distribution box isn’t installed yet but I could probably hook it up and the plenum and at least get a functional electrical test that way. I don’t want to make a big deal out of this if it’s expected behavior.
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That matches what Royce has observed. Icing switch should be closed unless it is below freezing, so that makes sense for it to be closed. But makes me wonder if the AC Control Switches commonly get stuck closed.
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Would the A/C clutch engage if the freon charge is low?
Yes, there was no freon pressure switch.
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My new receiver-drier has provision for low pressure cutoff switch. I do plan to install, just haven’t got to it yet.
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