2005 Vibe Defrosting Issues - Questions

[2005VIBELO]

We have a 2005 Vibe, and until this morning it hasnt been an issue, but with the temps dropping in the area (Michigan) my wife complained to me that her defrost is not working correctly. I scrapped the windows this morning and started it up for her to let it warm up. She noted that the defrost will warm up for about 5 minutes and then get cold again for 15 minutes and then warm back up. Could this be a thermostat problem, where it is opening too soon? Any thoughts would be greatly appreciated

[Sublimewind]

Howdy,I would check the coolant level first off..

[2005VIBELO]

Okay, the fluid level in the bottle and in the radiator are fine. Any other suggestions?

[Sublimewind]

Next easiest would be to check the diverter flap issue.. Easily found here, the diverter in the heat/AC unit comes lose, so it can keep the heat blocked out.. Then after if not that, I would consider a thermostat, you prolly need a flush/fill too anyway.. I know I do..

[2005VIBELO]

Sub, thanks for the help, but one question... where is it found? Im thinking that might be the issue. A flush fill should be done as well as the car has over 100,000 miles but not sure when it was done last.

[2005VIBELO]

Okay, i admit it, i did a sloppy job checking the coolant and only checked the over flow bottle. The radiator was low so i filled it up and the heat works now. Thanks for the help. Another question... the check engine light was on, took it to Autozone and the counter guy said it was running lean and it was more than likely the O2 sensor was faulty.. well after i filled the coolant up the light has since gone out. Is it typical to run the car lean if it is running hot with no coolant? just curious.