Wife's car has been having some heat issues. She said it was having trouble getting heat, and she's had to up the temp to 80+ to get any heat at all. We took it out for dinner a few weeks ago when it was pretty cold and confirm that the heat would not come on for us. On the return trip, it finally kicked in, we had the heat set to 85 before it worked.

Took into the shop, but of course the heat worked for me on the way in, and worked for my mechanic when he tried a few hours later. Heat at 70, no problem. He confirmed the heater coil was getting and pushing heat.

Today, the car is again not giving heat. Cold AC air works fine.

We are frustrated by this climate control issue. I did not see anything like this in the forums, wondering what to check next. Do I replace the DCCV and hope the whole system isn't fried, or does this sound like the flakey thermostat?

 

Here are a few quick thoughts:

Check the coolant level. My '02 V6 is very finicky. If the coolant level is low, the heat tends to go cold at idle, but works better at higher RPM.

Set the climate control to HI. This puts the system in manual mode and bypasses most of the automatic controls. This will help isolate whether the heater core is getting hot.

If still no heat in HI, unplug the electric connector on the DCCV. Both chambers in the valve are spring-loaded open, so hot coolant should flow to the heater core. If not, the valve has likely stuck closed.

What is your temperature gauge showing? Does the upper radiator hose feel hot to the touch? This is to make sure the coolant is actually hot enough. If not, that points to a thermostat problem.

If these steps all check normal, pressurize the cooling system with a pressure tester. Last year I had a slight coolant leak that didn't show up visually with the engine running. It dropped the system pressure just enough, though, and I think this affected coolant flow to the heater core even though the coolant level was fine. I fixed the leak, pressure returned to normal, and the heat was fine again with no other action taken.

 

Could be a DCCV that's sticking. If so it'll fail and take out the module quite likely.