My front roof air conditioner has started blowing cold air for 5 minutes then blowing hot air (as if it switched to heat pump) then back to cold. It cycles back and forth about every 2-3 minutes. The rear airconditioner works fine so we swapped the circuit boards but that mad no difference. Has anyone else run into this?
2003 U320
Jim churchill
You have a reversing solenoid valve that changes unit from ac to heat pump. Coil often becomes weak and need replacing. Remove cover and you will see it. Only solenoid on unit. Coil is $15 or so.
that can also be caused by the connectors that come from the thermostat and go up to the top board. You might try by unplugging the connector and cleaning with some contact cleaner. That is what I found was wrong with ours.
Is the solenoid on the circuit board or by the compressor?
It is by the compressor.
It is on maybe a 3/8 inch freon line under the cover on your top unit.. Coil has two wires coming from it. The square [or sometimes round thing on top] is the coil. It is held onto the valve by a clip on top.
This is basically what it looks like. Most AC shops, or electrical supply places will have just the coil. Air, Oil and Water Solenoid Valves - Grainger Industrial Supply (https://www.grainger.com/category/air-oil-and-water-solenoid-valves/solenoid-valves-and-coils/plumbing-valves/plumbing/ecatalog/N-ri3)
Take you old one with you to match up.
Better info
AC Repair - Reversing Valve Solenoid Failure - Roadtreker (http://www.roadtreker.com/modifications/Air-Conditioner-Repair)
This not your ac, but solenoid valve is similar.