I'm having a heating issue with my 2003 Odyssey where the heat coming from the vents, even with the temperature gauge on full heat, was luke warm. I did read some other posts that stated you should check the heater control value on the firewall. That value appears to be moving as the temperature gauge is moved. I then changed the thermostat. Now what is happening is the heat at idle or lower speeds is luke warm but gets hotter as the RPMs move higher. So, on the freeway, I feel a good amount of heat coming from the vents. On residential roads, the air is luke warm. Is it possible I got a bad thermostat? It doesn't seem like the heater core is bad. What else could be wrong?

 

Thermostats are relatively cheap parts and can be bad, but that is unlikely. If a thermostat is bad then it will stay completely open or completely closed. If your vehicle is overheating then it is possible the thermostat is stuck closed. However, if your vehicle is not overheating, but your heat is luke-warm even when the vehicle is up to operating temperature, then it is possible you need a coolant and radiator flush. A radiator flush will insure proper flow and maximize the cooling/heat absorption properties of the coolant.

 

Thank you for the reply. The problem ended up being the heater control value. I did flush the heater core thinking the main problem was there. I'm sure it didn't hurt because I did flush some junk out. I thought the heater core was the issue because the hose going in was hot and the hose coming out was cold. Apparently, I should of remove the heater control value and actually looked inside to see if the value was moving. The actuator on the outside was moving but that didn't mean the inside value was opening and closing. A mechanic told me if you bypass the heater control value with some heater hose and the heat works it's obvious what the problem is. Oh well. Live and learn.