I have a 2005 Caravan. For the last three years, the AC has worked intermittently. When the compressor clutch actually engages, it will freeze you out.

What we have eliminated:

There are no leaks in the system, and the system is fully charged.
I've replaced the relays and fuses with known good ones with no change.
I replaced the control panel. This seemed to make the outages less frequent for a while.

Patterns we've noticed:

The AC works normally if the car has been parked in the shade or in our garage.
If parked outside in full sun on a hot day, it is least likely to engage.
If parked outside in the heat, it will typically kick in on long highway trips, but is less likely to do so in stop and go traffic.

Clearly the issue is related to the build-up of heat in the engine compartment. Are there relays or other components that could be affected by the heat in this manner?

 

How do you know if you have appropriate charge in the system? you had a Shop recharge it?
you might have overcharged the system, when it is too hot, the pressure builds too high and knock out the Hi pressure switch.
or you can have a bad Compressor clutch coil that goes out when it is too hot.

 

Yeah, a shop did the charge on it. Might be worth looking into, though. Thanks!

 

probably an open in the clutch harness, usually on the compressor side of the connector. The heat causes the insulation to expand pulling the break in the wire apart.