HVAC blows heat only
 

Hi guys, I'm new to the forum. I'm stationed in Japan and have a 95 Hilux Surf, the same as the 96 US 3rd gen 4runner for those who didn't know.

This HVAC system has manual controls with auto-temp selector

Here's what's going on

No matter where I slide the temp selector switch to I get heat only. The A/C compressor comes on when selected and I get cold air up until the engine heats up and hot water starts flowing through the heater core. Which is leading me to believe the valve is stuck open. Is the valve vaccum or electronically controlled? I'm hoping it's just dirty contacts in the temperature selector switch. I'm going to pull the unit tomorrow to clean it out. If anybody has any advice or an opinion, let me hear it. Your help is much appreciated.