I have a 2004 GMC Canyon SLE 5cyl with about 118k miles on it. This week the air conditioner stopped working out of the blue. Then the next small trip I made, it started working fine again. Then I got the “ac off/eng hot” message. It is running hot, too. I could only drive maybe 2 miles with the air maxed out before the gauge hits max and I get the message. I noticed my coolant reservoir was empty so I thought that may be the issue. Filled it up and still had issues. Noticed there was some coolant resting on top of the radiator, so I replaced the radiator. That didn’t change anything so I then moved on to the thermostat, then the water pump. The problem is still exactly the same. I’ve never noticed any leaks. What’s the next step? Could it be simple as a radiator cap? Appreciate the help. This forum helped me through the repairs up to this point.