ac runs and so does heat at same time no ac in car

Asked by Jul 24, 2016 at 11:19 AM about the 1998 Mercury Grand Marquis 4 Dr GS Sedan

Question type: Maintenance & Repair

ac runs and heater will not shut off

3 Answers

32,545

The heater core never shuts off. Even on the blazing hottest day it sits there in your dash, a little radiator dispensing heat. All that happens when you switch the temperature knob from heat to cold a little plastic door (called a blend door) swings over to direct air flow from the blower motor to go over the AC evap coil instead of the heater core. If you have good AC and COLD air (check the compressor is running) and HOT at the same time, it's a sign your blend door is stuck open to the heater core. Usually it's the blend door actuator that failed. The part costs about $35. The labor, however, to get to the heater cores plenum box is expensive. You either have to remove or loosen the dash, pull radio, passenger air bag, drop glove box, to gain access to it.

2 of 2 people found this helpful.
10

KenF How much does the labor to repair the blend door?

1 of 1 people found this helpful.
32,545

Blend door repairs are expensive due to the labor to access that area of the dash. About 4 hours shop time or more, the dealership will charge over 1,000 for this. The blend door actuator (typically the part that fails) costs under 40 bucks. If you can find a good guide online, it can be a good DIY job even for a novice. Try Crownvic.net, they have several posts there on doing a blend door or actuator replacement. The trick they use is to loosen the dash, wedging the passenger side up on a small block of wood and reaching in through the air bag opening to get to the actuator. I've done several CVPIs this way, and have it down to about 45 min-1 hour. Be sure to TEST the actuator too, before swapping it out. If you prefer to have a shop do it, just call local mechanics and shops, especially those that specialize in AC repairs, these types of places tend to have much better pricing that dealerships and chain shops.

1 of 1 people found this helpful.

Your Answer

Grand Marquis

Looking for a Used Grand Marquis in your area?

CarGurus has 1,526 nationwide Grand Marquis listings starting at $995.

ZIP:

Mercury Grand Marquis Experts

  • #1
    Tracy Hooks
    Reputation
    5,910
  • #2
    kbro
    Reputation
    2,210
  • #3
    Js08016
    Reputation
    1,980
View All

Related Models For Sale

Used Lincoln Town Car
14 Great Deals out of 1,583 listings starting at $1,200
Used Ford Crown Victoria
3 Great Deals out of 877 listings starting at $2,000
Used Ford F-150
3,016 Great Deals out of 229,514 listings starting at $1,300
Used Chevrolet Tahoe
818 Great Deals out of 39,852 listings starting at $1,900
Used Ford Mustang
337 Great Deals out of 42,077 listings starting at $1,488
Used Ford Taurus
194 Great Deals out of 16,058 listings starting at $1,200
Used Honda Accord
838 Great Deals out of 87,589 listings starting at $1,444
Used Chevrolet Silverado 1500
2,725 Great Deals out of 156,642 listings starting at $1,000
Used Chevrolet Camaro
385 Great Deals out of 31,362 listings starting at $3,495

Used Cars For Sale

2011 Mercury Grand Marquis For Sale
21 listings starting at $4,495
2010 Mercury Grand Marquis For Sale
4 Great Deals out of 75 listings starting at $2,290
2009 Mercury Grand Marquis For Sale
3 Great Deals out of 81 listings starting at $3,200
2008 Mercury Grand Marquis For Sale
3 Great Deals out of 133 listings starting at $2,990
2007 Mercury Grand Marquis For Sale
119 listings starting at $1,600

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.