Patient is '91 300TE wagon. Climate control can operate perfectly with heat, cold, recirculate and all settings/speeds. Then, other times nothing happens at all, no fan, no compressor, only heated air leaking into the cabin from the AC vents while underway.

The red number 7 fuse has been changed out to a new fuse. The 30 amp fusible link has been checked. ignition switch has been wiggled in an effort to find a bad place n the switch.

When the AC works, it usually comes on as soon as the car is started and runs flawlessly. This lasts for days, even months. Suddenly without warning I start the car and nothing works at all. No settings on the pushbuttons or temperature wheel have any effect. The thing just stays off until it is ready to come on again sometime, when the car is started a day or a week later. This can happen on a cold start or a hot start. It can be a dry day or humid day and it just works again. In my mind I think there may be a greater likelyhood of failure during high humidity but it is not absolute.

I have never been able to do anything to deliberately cause this to change from working to nonworking or back again. I suspect a voltage issue involving the ignition switch, but do not know which wires would be involved or where they terminate. No schematic. I have studied many climate control posts and see similar themes, but not quite the same as this. Please offer your insight if you have encountered this problem. There is no hairline crack in the 30 amp fuse, so we need another possible culprit.

Love to hear some ideas..BTW this is hot south Texas.