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

Asked by 121norman 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

103,225

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.

3 people found this helpful.
10

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

1 people found this helpful.
103,225

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.

2 people found this helpful.

Your Answer:

Grand Marquis

Looking for a Used Grand Marquis in your area?

CarGurus has 292 nationwide Grand Marquis listings starting at $3,860.

ZIP:

Own this car?

Share your experience with others.

1998 Mercury Grand Marquis

Review another car

CarGurus Experts

  • #1
    Tracy Hooks
    Reputation
    9,860
  • #2
    Trippmeister
    Reputation
    5,150
  • #3
    Bob Beaman
    Reputation
    3,880
View All

Know more, shop wisely

Search

Related Models For Sale

Used Lincoln Town Car
10 Great Deals out of 415 listings starting at $1,050
Used Ford Crown Victoria
6 Great Deals out of 136 listings starting at $3,200
Used Ford F-150
6,341 Great Deals out of 170,896 listings starting at $1,999
Used Chevrolet Corvette
769 Great Deals out of 14,434 listings starting at $4,999
Used Ford Mustang
950 Great Deals out of 19,711 listings starting at $1,950
Used Toyota Camry
2,045 Great Deals out of 44,008 listings starting at $800
Used Buick LeSabre
3 Great Deals out of 186 listings starting at $1,895
Used Chevrolet Silverado 1500
4,162 Great Deals out of 122,662 listings starting at $1,999
Used Honda Accord
1,523 Great Deals out of 30,178 listings starting at $1,200
Used Cadillac DeVille
254 listings starting at $2,995
Used Toyota Avalon
173 Great Deals out of 2,068 listings starting at $1,999

Used Cars for Sale

2011 Mercury Grand Marquis For Sale
13 listings starting at $4,900
2010 Mercury Grand Marquis For Sale
19 listings starting at $4,984
2009 Mercury Grand Marquis For Sale
16 listings starting at $6,495
2007 Mercury Grand Marquis For Sale
24 listings starting at $3,995

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. Content will be removed if CarGurus becomes aware that it violates our policies.