Hello.

I have isolated the reason that my AC won't start to one of the hi or low pressure cutoff switches. I did so by bypassing them and connecting the hot thermostat lead directly to the contactor. Started right up.

Next I ohmed out the two switches. The one in the small line from the compressor through the drier to the condenser is showing open (infinite resistance). It has a sensor in the copper line, with a wire (looks like a thermocouple) running to the switch body mounted on the inside wall of the cabinet/shroud.

I had the freon topped off about 3 weeks ago.

Is this the high pressure switch? Is it possible the AC man overfilled the unit? Wouldn't the switch close after the unit was turned off and sat for hours/days - thus allowing it the switch to close again and the unit to run until the next time it exceeded pressure?

Thank you.
Randy White

Quote:

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Originally Posted by rwhitebbq

Hello.

I have isolated the reason that my AC won't start to one of the hi or low pressure cutoff switches. I did so by bypassing them and connecting the hot thermostat lead directly to the contactor. Started right up.

Next i ohmed out the two switches. The one in the small line from the compressor through the drier to the condenser is showing open (infinite resistance). It has a sensor in the copper line, with a wire (looks like a thermocouple) running to the switch body mounted on the inside wall of the cabinet/shroud.

I had the freon topped off about 3 weeks ago.

Is this the high pressure switch? Is it possible the AC man overfilled the unit? Wouldn't the switch close after the unit was turned off and sat for hours/days - thus allowing it the switch to close again and the unit to run until the next time it exceeded pressure?





Thank you.
Randy White

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Is this the high pressure switch?
Smaller line is the high side.

Is it possible the AC man overfilled the unit?
Yes

Wouldn't the switch close after the unit was turned off and sat for hours/days - thus allowing it the switch to close again and the unit to run until the next time it exceeded pressure?
Yes it should unless it is a manual reset style with a reset button.

Post exact model number of the outside unit.

Thank you.

Further research has confirmed that Lennox high pressure switches do require a manual reset. I'll give that a try this afternoon.

I appreciate your quick response.