Question about 1999 Mercury Grand Marquis

1 Answer

Heater does not blow Hot Air.

The car gets up to normal operating temperature in about 5 mins or so. It does not run hotter or colder than it always has. I had to charge the A/C this summer. I felt the hoses and the top radiator hose is warm. the two hoses that flow through the firewall on the passenger side ( heater core ) are both warm. A/C works fine this summer after i charged it. the A/C blower does seem to run on high regardless of setting, ie.. even on low it will run low for a bit then blow full blast. Checked coolant level, all good 50/50 mix. Checked 30 amp fuse for heater appears in tact. What's up??

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  • Mercury Master
  • 14,585 Answers

If you can put your hand on the heater hoses and keep it there, then the T-stat is bad. Heater hoses and radiator hoses should get hot enough that you can't hold them. 212 degrees+

Posted on Nov 18, 2014

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Posted on Jan 02, 2017

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gordanddar
  • 477 Answers

SOURCE: temp guage showing hot, not getting any heat for 1992 Mercury Cap

If the hoses to and from the heater core are hot , and you say the heater core is hot , then the only answer is that the air duct that flows into or out of the heater core plenum ( housing ) is not opening.
Heater control on dash borad inoperative.
Not sure about 92 capri , some cars have a cable linkage , some work on vacume motors.
Try to find a haynes manual for your car , they will walk you through almost every step of anything you may ever want to do to your car.

You seem to know what you are doing , but I gotta ask ........the heater core you felt was up behind the dash inside the passenger compartment of the car right ?

Posted on May 10, 2009

  • 13 Answers

SOURCE: My heater is blowing cold air in my 2002 mercury

Remove the center console and on the drivers side toward the bottom of the heater box will be a small electric blend motor. Replace this motor. New part should be about 90 usd. After the center console is out should be three small bolts holding it in.

Posted on Oct 06, 2010

skychief2001
  • 21873 Answers

SOURCE: My 1984 grand marquis does not have interior heat.

Sounds like a faulty blend door under the dash. The blend doors direct air thru the heater core and the vents. Your model should have vac controls so you could have a vac leak or a stuck door.

Posted on Oct 10, 2012

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My 2010 dodge journey is running hot and the heater is blowing cold air. Temp goes back down to normal while driving. No indicator lights r on. Is it the thermostat or heater core?


Most likely neither is the problem, to verify the heater core is ok go under the hood and touch the heater core coolant supply hoses (hot engine) one will be really hot and one a little cooler, if this is the case the heater core is ok and you have another problem, that other problem is most likely a failed part or parts called the air temperature control blend door motor or door is defective. Also I doubt the engine is overheating, it gets hotter while sitting in traffic because the electric fan that cools the engine only comes on at about 225 degrees Fahrenheit. If you had an overheat condition the check engine light would also come on to alert you of the overheating condition.

Dec 05, 2016 | Dodge Cars & Trucks

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It just blows cold air. no hot air


With the vehicle cold, check your coolant level and fill it up it it is low. Start with your heater hoses. Check to see if one hose is hotter than the other. If so, then you have a bad or malfunctioning heater control valve (if equipped) or a bad heater core. If the vehicle never gets up to operating temperature, your should change your thermostat.

Dec 26, 2014 | 2001 Ford Windstar

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Rattling sound when I slow down. Sounds like a bad water pump but the sound stops when I disengage the clutch and stop even though the engine is still running.


The car is over heating. Check the coolant level. Have a pressure test done to check for ;leaks. Have a compression test done to check for head gasket and cracked head/s. Normal operating temperature is between 85 and 95 degrees c and if as you say is 20% hotter then it is boiling

Feb 17, 2014 | 1989 Acura Integra

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Heater will not blow hot air


Assuming the radiator is full of coolant, and the engine is reaching normal temp of 190 degrees, you could have a blocked heater core or the temp control valve may not be working on the heater hose.
I would check to see if both heater hoses are getting hot.

Jan 09, 2013 | 1990 Dodge Caravan

1 Answer

2000 malibu runs hot if not warmed up


How do you know it gets hot? Are you going by the temperature gauge on the dash? Or have you checked under the hood and found out the engine really is running hot? ...Reason I ask is, something just doesn't sound right in your description. After just 5 minutes from starting and driving away, the engine would not yet be at normal operating temperature. That would explain the heater not yet warm. But the temp. gauge says hot?
If so, I would replace the temperature sending unit on the engine. the one for the dash gauge, and see if that was the problem-not reading the temp. accurately.
Couple of other things: Are you sure you got all the air out of the coolant system? Start the car with the radiator cap off and let it run until the engine is warmed up fully, then shut it off and install the cap. Does your reservoir tank stay about half full where it should be, between the full-hot and full-cold marks?
If your problem persists. I would have the coolant system pressure tested, and see if you could get a true temperature reading of the coolant when it seems to be running hot.
Good luck.

Mar 05, 2012 | Cars & Trucks

1 Answer

Heater will not blow hot


Top up Fluid level in over flow tank and radiator ( when cold ). Run engine to normall operating temperature and check for heater blowing hot air.Good starting point.

Dec 05, 2010 | 1999 Chevrolet Silverado 1500

1 Answer

2006 grand prix heater only blows cold air. both heater hoses are hot blower motor works fine.


Sounds like the temperature blend door actuator may be bad or the vacuum hose to it is disconnected.

Poor Heater System Performance CAUTION
Check all fluid levels and adjust as needed, before operating vehicle for extended periods at idle.
  1. Start the engine.
  2. Idle the engine until the thermostat opens (upper radiator hose will be hot) Is the engine at normal operating temperature (approx. 200° F)? If yes, go to the next step. If no, go to step 16.
  3. Set the mode selector to FLOOR mode.
  4. Set the heater control selector to the warmest temperature setting.
  5. Set the blower speed the lowest setting.
  6. Carefully feel the inlet and outlet heater hoses at the heater core. Is the inlet heater hose significantly hotter than the outlet heater hose? If yes, go to step 14. If no, go to the next step.
  7. Set the mode selector to PANEL mode.
  8. Select the maximum blower speed.
  9. Select the warmest temperature setting.
  10. Place a thermometer into the center I/P PANEL air outlet and affix a second thermometer to the heater core outlet heater hose.
  11. Record the temperature at the center I/P PANEL air outlet and at the heater core outlet heater hose. Are the two temperature readings about equal? If yes, go to the next step. If no, go to step 13.
  12. Inspect and repair the cowl, cowl area, recirculation door, and the HVAC evaporator/heater core case for cold air leaks. Repair any problems found, go to step 17.
  13. Inspect the temperature door operation. Repair any problems found, go to step 17.
  14. Turn OFF the engine. Back-flush the heater core. Start the engine. Select the FLOOR mode and the lowest blower speed. Select the warmest temperature setting. Feel the temperature of the inlet and outlet heater hoses at the heater core. Is the inlet heater hose feel significantly hotter than the outlet heater hose? If yes, go to the next step. If no, go to step 17.
  15. Replace the heater core. When the repair is completed, go to step 17.
  16. Check for low engine temperature problems, Repair or replace as needed, go to step 17.
  17. Operate the system in order to verify the repair. If the system operates properly, the repair is complete. If the heater still does not work properly, repeat the entire procedure.

Nov 19, 2010 | 2006 Pontiac Grand Prix

1 Answer

My heat blows hot for about 5secs then grt cold again whats that


If there is no sign of coolant loss (air pocket in heater core),then check for plugged heater core. Both hoses should be very close to same temp with engine at operating temperature with heater fan on high setting.If the return hose is alot colder, then coolant flow is restricted.

Jan 31, 2009 | 1999 Ford Expedition

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