Expert: Roland Finston - 11/26/2011

Question
QUESTION: Our 2003 Chrysler Town and Country minivan heater stops working after 25 to 30 minutes of operation.  The blower continues to work, but it blows cold air.  The heater will start working again after some period of time of continued driving.  I'm not sure if turning the ignition off and then back on restores heat or not.  I'm thinking thermostat.  What do you think?

ANSWER: Hi Steve,
If the temp gauge is staying above 1/4 scale then there is sufficient hot fluid to run the heater. So watch the gauge for that possibility. Otherwise, touch the incoming and outgoing heater hoses that go thru firewall when you aren't getting heat and feel if they are about equally hot. If one is cold, then you have an issue with flow throught the heater core not being consistent. The last thing could be the blend air door on the HVAC that may be moving on it own accord. Let me get back to you after dinner with a way to calibrate that door and we'll see if that does the trick.
Roland

---------- FOLLOW-UP ----------

QUESTION: It's outside warming up now. Should have more info in about 20 minutes.
Thanks for the help.

ANSWER: Hi Steve,
I am not sure what you learned from checking, but let me mention how to do the calibration of the control doors: The process is the same whether you have a conventional or automatic temp control unit. Turn the ignition switch "on". Simultaneously press the Power and the Recirc buttons for at least 5 seconds. Some flashing of various lights or graphics will begin and continue for either 20 seconds (automatic temp control type) or for 2 minutes (conventional type). If the flashing stop that means the calibration was successfully done, so you can then see if the heater function is better. If the flashing doesn't stop that that means there is a fault in system and a code readout should be done to find out what is the fault code number. I suspect the issue would be the blend air door modulator is not working well and I can tell you haw to change that out and at the same time check to see if the blend door is able to move easily through its range of motion.
Roland
PS Thanks for the rating of the earlier answer and you may, if you choose rate this answer and consider a nomination for me to be 'volunteer of the month. Thank you.

---------- FOLLOW-UP ----------

QUESTION: It turned out to be something simple - the coolant was way low.  Should have thought of that immediately, but your earlier instructions led me to the problem.  Not sure why we are losing coolant - but that's another problem.  Sorry for the delayed reply, but I was locked out for a while.  Thanks very much for the help.

Answer
Hi Steve,
Thanks for the follow-up. The unexplained coolant loss:
If there is no sign of it under vehicle, the watch for excessive white smoke when you first start it up from cold in the morning which would be a sign of an internal engine leak due to a faulty head gasket. Let some smoke condense on your hand and if it smells of antifreeze (assuming you do have a 50/50 mixture in system) that would corroborate that hypothesis. Also check the oil to see if it might be milky/frothy as the result of the same sort of leak. Lastly check for wet carpeting under the dash which would be a sign of a leaky heater core.
Roland
PS Please 'rate' my answer, and where you see the question about a 'nomination' of me to be volunteer of the month consider giving a 'yes' response. Thank you