So i have been getting lukewarm heat for some time (months). And in the summer, the A/C was becoming increasingly warm. Just seemed lukewarm was the only setting. So I pulled the Servomotor after seeing that it doesn't move when I change the temp control from cold to hot and back. I was able to move the air mix control "arms" and have good hot air blowing. They are stiff, however, which may have led to the servomotor failing.

What should I lube those arms with (thinking white lithium) and how can I test the servomotor before I replace it?

 

I would just replace the motor. Same thing happened to my wife's CRV. No hot air, water temp was normal and upper radiator hose was hot.

 

I wanted to start giving back. I have been having this problem and I read a lot and followed directions - I took the servo apart and spun the arm so that the plastic gear wheel had fresh teeth.

But.. I wondered what made those teeth strip in the first place? So i tried manually moving the control to switch from hot to cool air and it was tight! So I unhooked both ends of the cable and I lubricated it using a lubricant for plastic - and put everything back together. Good so far!

I would lubricate the system to make sure that servo doesn't have to do too much work.

Good luck.