Question about 1999 Mercury Grand Marquis

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How do i confirm a blend door problem?

The car will not blow hot air. The thermostat is good, the heater core does not leak and the hoses going into the core are both hot. The upper radiator hose is hot. The car gets to normal operating temp in a reasonable amount of time. The car does not run hot. How can I confirm that it is the blend door / actuator without spending all day taking apart the dash?

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  • 10 Answers

Blend door concerns heat and cold air ducting flapper. whether electronic or manual turning of a knob there is a movement noise. a motor/s make/s a sound on electronic controlled ones or a turn knob harder at times to turn does this. then feel the changes hot/cold breeze and no breeze etc..on the vent according to what you turn the system on to do. it is best to confirm movement /motion of the internal motor or flapper during night time or early morning in the garage inside the car devoid of noise to hear the motor or flapping movement, must hear some motor effort or feel hand effort if cable to the heater valve is intact/ not snapped to open heater valves on the engine side. then inspect heater cable if heater is not working etc..hope this helps. In the absence of diagnostic codes, try the step above. There are 2 basic steps in blending hot and cold air. 1) open/closing of heater core valve so that when air passes the heater core air gets hot before it gets out of the vents. if you can, locate this valve and actuator cable or motor if it moves according to your knob or button push (try an IR temp sensor to confirm hotness of engine vs heater core inlet and outlet if needed to diagnose a blocked heater core).. 2) the blend door properly moving, in early morning, try above " it is best to confirm movement /motion of the internal motor or flapper during night time or early morning in the garage inside the car devoid of noise to hear the motor or flapping movement, must hear some motor effort". personally I would try step 2 first in your case. hope this helps..

Posted on Nov 28, 2014

Look at the motorcraft site & get to the parts area

Use your VIN # then your got exactly your vehicle

Enlarge the view of all the under dash HVAC Motors
or servos & write down the OE numbers for later

If you can have the module scanned professionally
& if that data is there, it may tell you the failed ones

Either way you try all the manual settings for air flow

The ones that fail to switch, along with your motorcraft
view of them ,will guide you to the one you have to replace

If that is the problem,only then do you go under the dash,
remove the glove box, etc

Also look at & feel all the coolant tubes that may be on the
passenger side sub frame rail or going from the radiator,
coolant fill,all heater related tubes & hoses,they may not all be hot

They all have to be hot or you have a failed heater control
valve somewhere

I have one here for my Lincoln LS to install if it stops raining
& snowing

First establish if you have hot coolant going into & out of the heater core,then work on the control valve if that applies then
the under dash blend doors

If you had the factory manuals I purchase you would be all set

Try the internet & you tube video also & ask for your vehicles
heater issues

Posted on Nov 25, 2014

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Posted on Jan 02, 2017

deathraider
  • 64 Answers

SOURCE: 1985 cadillac fleetwood V8 4.1 blows cold air out but no heat

if you had heat before the problem than there is probably air still in the system . dont know your motor set-up , but it might have a bleed valve on the thermostat housing or a bypass line . if not , start the car and let it warm up ......in the mean time take the upper radiator hose off @ the radiator . When it heats up to normal temp , the coolant should flow out of the hose . that will tell you that the thermostat is opening , and it will also get the air out of the system @ the same time . As soon as it starts to flow , hook the hose back up and tighten . refill the cooling system back to the full line , than check for heat
GM is bad about getting air trapped in the system .

Posted on Dec 03, 2008

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

alicantecoli
  • 22095 Answers

SOURCE: No warm air in car. both heater hoses are hot when

wedge it closed for now

Posted on Nov 18, 2009

bill_rees35
  • 5 Answers

SOURCE: Air blows hot air all the time

If the actuator is moving when you move the control it may be a broken or warped plastic door. If the actuator does not move look for a bad control unit or a vacuum leak.

Posted on Mar 05, 2012

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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