When I switched from Heat to Cool last week, the outdoor unit (with the fan) came on for 5 secs, then turned off for 5 secs, then came on for 5... (ad nauseum). What is the likely culprit?

When I switched from Heat to Cool last week, the outdoor unit (with the fan) came on for 5 secs, then turned off for 5 secs, then came on for 5 ... (ad nauseum). What is the likely culprit?

If it has a low pressure switch in the refrigerant circuit this will cause that exact symptom. Time for a professional to put some gauges on it and check it out.

Thanks... that's what I was afraid of.