A/C Climate Control Not Working Properly


fairly significant
Typical Repair Cost:
Average Mileage:
90,700 miles
Total Complaints:
6 complaints

Most Common Solutions:

  1. not sure (4 reports)
  2. replace o-rings in climate control module (2 reports)
2004 Mercury Grand Marquis AC / heater problems

AC / heater problem

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2004 Mercury Grand Marquis Owner Comments

problem #6

Sep 082019

Grand Marquis LX 4.6L V8

  • Automatic transmission
  • 80,460 miles


Heater fan started going on and off with road vibrations and now only works on manual maximum setting. Have replaced control unit in the dash and the resistor to the fan and door controller with no change.

- Larry L., Pleasant Grove, AL, US

problem #5

Jul 082014

Grand Marquis LS V8

  • Automatic transmission
  • 75,000 miles

My A/C went to heat in July. I took it to a A/C repair shop. They said the cylinders had o rings and they were bad. They said they could fix it for $400.00 I didn't have $400.00. They told me for $2900 they could fix the A/C. But the defrost would not work and no feet heat. This year it stopped working again. I checked and found the unit for $350.00 new from local Ford dealer. I installed it but it seems like there were some vacuum lines missing. The A/C works great except it seems to only work on max air nothing seems to change when I put it on AC. The defrost is not working. This makes me think they changed some vacuum hoses around. I can't find a diagram for the vacuum hoses. Can you help me with the diagram.

Thanks for your help.

- jeh311, Woodstock, GA, US

problem #4

Sep 012015

Grand Marquis LS 4.6L

  • Automatic transmission
  • 66,000 miles

Auto mechanic said he had to put 3 cans of refrigerant in. Still does not blow cold. Air comes from defrosters and not dash. Seems to blow from dash when running idle than as soon as you give it gas it blows from defroster. Looked this up on You-tube and it looks like I will be doing some EATC work with o-rings on solenoids. This should be a re-call after I already fixed the light module myself. You know the last recall that they decided to do after they let all that time pass first. Also the light for the shock absorbers goes off all the time. I am afraid to see how much that cost. Why can't FORD just fix their cars right? Cost $55 just to make appointment with the dealer. Good car, just fed up!!!!!

- thomas tobin, Wenonah, NJ, US

problem #3

Jun 012011

Grand Marquis LS 4.6L V8

  • Automatic transmission
  • 130,000 miles


I had to guess at the mileage and date I started having issues with the climate control because it happened some time ago. Anyway, I had issues with the air conditioning beginning to blow through the defroster vents. Initially, it would occur while accelerating, then resume blowing out of the dash vents. Eventually, the A/C blew through the defroster vents all the time. My car has the electronic automatic climate control system and this is apparently a common issue.

Some would have you believe the entire control module needs to be replaced. But there's an easy repair that can be done on the existing module, if you're fairly handy. It involves removing the control unit from the dash, disassembling it and replacing the rubber O-rings in the vacuum solenoids with silicone O-rings lubricated with electrical contact grease. The problem is that the O-rings in the solenoids develop vacuum leaks so the unit can't properly control the flapper doors in the ducts, resulting in air blowing out of the wrong vents. Replacing the O-rings solves the problem and there are instructions online on how to do it. I haven't had any more issues with it since making the repair, which only cost me about $20.00, as opposed to hundreds of dollars to replace the entire module.

One thing to note though, is that the solenoids aren't designed to be serviced, so 1) there may be just one chance to do the repair correctly, and 2) if the issue resurfaces, module replacement might be necessary. Trying to service the solenoids a second time may break them.

- b_to_the_squared, Appleton, WI, US

problem #2

May 152014

Grand Marquis LX 5.0V8

  • Automatic transmission
  • 80,000 miles

My A/C -Heater unit in the dash constantly goes on and off all the time when either the A/C is turned on and does the same with the heater turned on, but not as much as the A/C. I have checked around and I've been told by several mechanics, Dealerships and repair shops this is an expensive repair and the entire A/C climate control unit in the dash has to be replaced. I think this should be covered under a recall if there was ever one sent out.

So at this point I still do not have an A/C or heater that actually works. So I just keep all of it turned off so I won't have to deal with the unit always coming on / off all the time. :(

- jeffsanders, Gilbert, AZ, US

problem #1

Jan 012013

Grand Marquis LS 4.6L V8

  • Automatic transmission
  • 112,700 miles

When the air conditioning is set on the automatic climate control, the unit malfunctions and constantly switches from vents to defrost every 30 seconds or so, or on occasion the system would refuse to blow out of the vents all together and only blow through the defrost. Possibly need to replace the whole electronic auto climate control.

- Andrew S., Moberly, MO, US

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