I have not read any like this problem and am stumped.

When I turn the heat on it is very intermittent. This morning for example 40 degrees outside, heat set to 68 and it works for a few minutes then goes cool, cooler, cold. So I bump it up, not 2(that won’t work) but 3 or more degrees and begins to heat again, for awhile, then the same thing. Now I can put it all the way up to 'HI' and get all the heat I can stand and more.
Controls seem to work well in all modes (floor, vent, defrost, AC...). Blower speed and control good. A/C works great (especially on 40 degree mornings)

Like maybe the Ambient Temperature Sensor or a restriction in the water line?! Both sides seem to change at the same rate is why I said the Ambient and not the left or right sensors. I think it is more restriction than bad valve because when outside temp. is close to ambient temp. it may work well providing heat, yet if it is a restriction why would I get plenty of heat on 'HI'

Thanks,

 

Go back through the posts on "cabin temperature sensors" or such. There is a thread that discusses methods to clean them and or replace.

In your case that is where I would start. That said, I also wouldn't rule out the DCCV... They do goofy things when they fail. Heck, my climate control worked perfectly yet my DCCV was bad and leaking....

Do a search on the sensors or look them up in JTIS. They are supposed to be pretty easy to access and clean.

 

I didn't get a chance to look at it yet and will be out of town this weekend so I am still cranking the heat up to High. Even at 17 degrees outside I have to crack the window, so the heating system works really well!

I think I have narrowed it down to the Ambient sensor though due to the symptoms displayed... just haven't had a chance to check it out yet. I did however do a search for a code testor because I thought this may help and wow did I open a can of worms on that one(there are so many). Finally, after researching settled on a AutoEnginuity Scan Tool (AE). Will be in first of the week and will work with it next weekend(hoprfully)... then I will let ya know more.

 

AE is the one I settled on and works pretty well.

 

yea I think your comments were some of the ones that helped me in my search.

I got to thinking... should I spend money or INVEST! and got serious in my search. I can also get the GM enhancement for my other vehicles.

Thanks!!!

 

My car was doing the same thing a couple weeks ago. I took it to a shop and they replaced the DCCV. When I go the car back it still had the same problem, so I returned it to the shop a week later and they replaced the ambient temp sensor. The sensor was $26.