Heater issue, please help

[fuzzy54]

I bought a 2007 Grand Prix back in July
and never tested the heater because it was hot out. Now that it is
getting cold I have noticed some strange behavior. At first I thought
that I was not getting anything but luke warm heat and thought that I
must have a stuck T stat but in looking at the issue closer I found
out that the defrost is luke warm but the heat vents (middle vents)
are rather warm sometimes and other times they seem luke warm.

In
testing this out I put a temp gauge on the heat vents and they were
around 125, switched to defrost and it was only 95. I am kind of
stuck as to what the issue is but I am new to GPs so I do not know
all of the in's and outs and this seems to be a pretty complex
system. The water pump was replaced a few months before I bought the
car so I figured that they did not bleed the system but we tried that
and it did not seem to do anything.

Whats the next step?
1)
Replace T stat
2) flush the system including heater core
3)
replace the blend door actuator

Also I did recently replace
the battery and I do not know if this issue existed before that or
not, could that have caused this issue.

Thanks

 

[Fivefingerdeathpunch]

Personally if it was me, I would flush the heater core and put in a new stock 195 thermostat and bleed the cooling system.

Then if the problem was still there, look into the a possible blend door issue.