Lincoln Forum: Vents blow at cool temp, don't blow at hi temp
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01-09-2018, 12:24 PM #1Junior Member
- Join Date
- Jan 2018
Vents blow at cool temp, don't blow at hi temp
Hello all! I've been creeping around this forum for years and it's been very helpful. I'm currently having a problem I need some help with. My vents only blow air out of them when the temperature is turned down low. If I'm at 60, they blow very hard. Bump it up to 70, still blows pretty good, 75, still blowing but not as strong, turn it to 80 or higher I can hear the blower motor but nothing is coming through the vents. No codes pop up when I run the EATC test. At lower temps, it also works through the defrost or floor if I set it there. At higher temps it just won't blow anywhere. From my research, I think that's if the blend door is bad that it would still blow air out at higher temps, but the air would just be cold instead of hot. Also I think if it was blend door that it would show up in eatc test. Hopefully someone can help, it's too cold in Chicago right now not to have heat! Also, I park in a heated garage and the car has no problem staying at 75 in the Auto mode when I leave home. The problem I do have is that when the car sits outside and cools off, it won't ever get back up to 75 in auto mode bc nothing blows out anywhere bc the car is trying to blow hot air to heat up the car and nothing comes out at all when it's trying to blow hot air. I don't think it's the blend door, but I've read that changing the blend door on a 98 doesn't require pulling the dash like 99-02, is it true?
01-12-2018, 06:53 PM #2
That's odd that your EATC test doesn't come back with any codes. Our member Town has posted a very informative tech thread HERE, that may help you determine what the problem may be.
I assume you have a '98 Town Car, and not a Continental?
01-13-2018, 05:33 PM #3
Beside the HVAC system (and the EATC test shows no problem) the cooling system affects the temperature of the HVAC air temperature. There are three primary conditions that lead to low HVAC temperatures, an air lock in the cylinder head/heater core or a low coolant level or a thermostat that is staying partially open.
Before starting car check the coolant is up to cold level (I think your 1998 model has the integrated coolant storage bottle), top up if low.
Next check for air lock, by starting the car and checking the two heater hoses leading to and from the heater core, they should stay cold (one or both) if there is an air lock and get progressively hotter if coolant is circulating correctly. The hoses should be too hot to hold when coolant circulation is operating properly with a good thermostat.
Now check the large hose from the thermostat housing it should stay cold since thermostat is closed. If it gets progressively warmer then the thermostat has failed and is open to some extent. If the thermostat is working correctly the large hose will stay cold until engine gets hot and the thermostat opens and the hose gets hot very quickly. Normal thermostat opening temp is 195 degrees but will open a little before that temp.
Since your HVAC can achieve 75 degrees but not higher you likely have a thermostat that is not maintaining engine temperature high enough and heater core is not hot. Let us know what these tests show.