I have a 2007 Honda Accord that started having temperature control issues some time back, and I finally decided to look into it with summer approaching. It started blowing hot air some time ago unless I set it on the lowest setting at which point it would blow cold. Then it seemed to start blowing cold only randomly (say after leaving the setting on Low and driving around for a while it might eventually kick in). I also noticed (and this has been going on a while - not always, but here and there) an odd rattling sound in the dash. After doing some digging, I learned that the blend door actuator might be the culprit. So I unmounted that and left it plugged in to see what it would do when I changed the temp control knob. I noticed that it (the arm) wouldn't move on every incremental change, but after moving the knob several notches it would move a lot as if to catch up to where it should be. I decided to just buy a new one. But before I attached it, I just plugged it in and played with the temp control knob to see what the new one would do. Same behavior as the old one. It's like it's not registering every little adjustment and then plays catch up. So now I'm not sure what the issue is. It's like the signal isn't being properly relayed or something. As a side note, because this is a dual AC system (can control each side individually or together), I also tested the passenger side. It also doesn't seem to be adjusting properly. I guess it also has an actuator on that side, but I haven't looked for that yet. I'm wondering if the same issue is affecting both sides however. If I play with the blend doors manually, I'm able to change the temperature (obviously not a solution, but just wanted to make sure I could get cold air out of the thing). Any ideas on what the issue might be? Something in the controls on the dash?
After some more troubleshooting, I determined that it was AC clutch relay causing my issue. Replacing it resolved the problem. I went ahead and installed the new actuator (it may have been problematic as well because I've heard it click/rattle before), but the relay was really the source of my issue I believe.