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Like many others I have a cabin heater problem. It only gets warm and it gets colder as I select higher fan modes. I've read the blogs and will begin troubleshooting tomorrow (hoses, coolant, thermostate, etc). This may seem like a stupid question but where is the blend door, how do you get to it and how does it operate
The Blend door is located inside the Air Plenum. To get to it you have to pull the dashboard. Easy but time consuming and detailed. Search for the link in this forum on how to pull the dash. Follow it closely and you will not have any problems. While you have the dash out might as well replace the heater core as it may be partially plugged.
An easier item to check first is the water pump. It is possible that you are not moving coolant. The fins on the back of the impeller may be gone and you are only moving small amounts of coolant through the system.
Thanks for the info. If it were the water pump would that not cause the engine to run hot as well? Is there a good source that describes how the cabin heating system works?
Not necesarily. The impellers were totally gone off of my 97, and no overheat at all. Even on hot summer days of 100+. Was trying to troubleshoot my low/no heat issue and when I pulled the water pump the impeller was worn away to just a wafer with no fins and was more like a circular razor.
check the hoses that lead to the heater core.
The fact that it only gets warm and gets cooler as you increase fan speed suggests to me that it is a circulation problem. It may indeed be the door thing, but if you check the hoses and one is noticeably cooler than the other, than I suspect it could be a partially blocked heater core.