When to replace blend door

[Heuster]

I have a heater core that is leaking - bypassed that several months ago. I also have a blend door that needs replacing. Since I have to tear everything apart to get to the heater core, should I go through the trouble of doing the blend door replacement through the bottom of the plenum or just wait until I have the dash and HVAC out to do it?

Does the HVAC come out on the heater core replacement? If not, doing the blend door now is a no brainer...

 

[OneLever]

I would wait since you're going to have that area open. What do you mean by "HVAC come out"? Changing the blend door now wouldn't help much because even with it working perfectly you won't get heat if the heater core is bypassed. And somehow I doubt you need AC in the winter.