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    crazy a/c problems. Need help

    Hello everybody,
    I have an 03 Grand Marquis ultimate edition that was my grand fathers car before he passed away. I've owned the car for a little over two years now and it has approximately 75k on it. The problem I am experiencing started last year about this time and went away and has reared its ugly head again. so with that I will let you know what has happened. It started out when I was driving down the interstate on a cool morning last fall. I thought I would turn the vent on and enjoy the cool wheather unfortunately the windshield started fogging up so I cut the a/c back on and then noticed it was getting hot inside, really hot, then I noticed the heat was blowing out of the vents. I thought I must have hit the heat button instead but reallized that wasnt the case. no matter what I did it wouldnt quit blowing heat unless I turned the system off all together. I later spoke with the dealership and they werent much help so I pulled the controll panel and checked it out visually, no apperent problems, reinstalled it and everything works fine. Jump forward to present day and now I am having a different problem. When I start driving the car after it has sit for any amount of time off the a/c will blow out of the vent but when i accelerate it switches from the vents to defrost and then to floor and back to vent and then back to defrost or floor. It stays in the defrost/floor pattern untill I let off the gas and have very little engine vacuum then it goes back to the dash vents.
    I have ran the self check but nothing is coming up. So with that very loooong discription can some one please help me figure out what is going on?
    I also have a question about not wanting to start but thats a different post.
    Last edited by troy's03marquis; 09-25-2011, 11:46 AM.

    #2
    sounds like a vacuum leak. Low/no vacuum should still default to defrost. Check the black box on the driver's side fender where the relays are. That needs to not be cracked. Theres also a vacuum hose connected to it, which needs to be in good condition. Back at the vacuum tree on the firewall is a one-way check valve. If that is bad, it will cause this problem too.
    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC grandpa spec white and cranberry

    1984 Lincoln Continental TurboDiesel - rolls coal

    Originally posted by phayzer5
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

    Comment


      #3
      Thanks Gadget73. I will be checking that first thing in the morning.

      Comment


        #4
        well, After several days of trying to find the problem, Its still doing the same thing, I have checked the vac tree and it looks good, The check valve appears to be workiong properly also. I dont know where else to look but it does seem to be a vac leak by the way it keeps defaulting to defrost. Give it the gas while driving and it goes to defrost, let off the gas back to vent or floor then vent. no codes from the a/c control panel either. So, Whats the best way to find this leak?

        Comment


          #5
          did you actually check the check valve at the vacuum tree? You'll need a vacuum gauge to do this and to plug one of the two ports on the vacuum side and use the gauge/pump on the other port. Leave the one that goes to the tree alone. Pump down a vacuum on the valve and see if it holds the vacuum for more than 10-15 seconds. It shouldn't budge in that amount of time. If that's good, then you'll have to start checking other things for a leak. a decent hand pump vacuum pump will work wonders in helping to diagnose this problem. like one of these:

          I have one of these: http://www.sears.com/shc/s/p_10153_1...1&blockType=G1


          that looks like one of these: http://www.autozone.com/autozone/acc...ier=70116_0_0_

          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
          Originally posted by gadget73
          ... and it should all work like magic and unicorns and stuff.
          Originally posted by dmccaig
          Overhead, some poor bastards are flying in airplanes.

          Comment


            #6
            I can tell you what's probably causing this. There are 4 vacuum solenoids inside the HVAC head that control where the air flows. The o-rings on these go bad and leak vacuum, hence why when you accelerate and the vacuum drops in the car, they loose it as well. The default setting for the ATC in these cars is defrost that way if the entire system fails you can still clear your windshield.

            If you call Ford and ask for a replacement ATC head be prepared to drop your phone as last I checked they wanted over $500 for it, and there is no improvement on the design so the issue will happen again at some point. This is very common for the 03+ cars and trucks.

            What I did to fix mine was grab an ATC head from an Explorer and swap the entire assembly keeping the stock Vic exterior. I had to move 3 wires to make the switch from the way the Explorer unit is wired vs. the Vic and off I went. No issues to this day.

            You can try and change out just the o-rings like I did, but it was only temporary.

            If you want details on what year Explorer I grabbed this from and some tech insight let me know and I'll dig through my achives and pass along any info I gathered on this as I had fought it for almost 4 months before fixing it.
            These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

            Comment


              #7
              Based on Fordman's response, maybe check this out http://cgi.ebay.com/ebaymotors/2003-...item4aac1f40e3
              2020 Volvo XC90 T6 Momentum (Ice White / Blonde)
              2022 Ram 1500 4x4 5.7 Etorque, Built to Serve Edition, (Granite Crystal / Black)
              Past Panthers
              1989 Grand Marquis LS (Cabernet/Grey), 1989 Lincoln Town Car SS (White/Blue), 2004 Mercury Grand Marquis Ultimate (White/Black)

              Originally posted by Lincolnmania
              if its got tits or tires it's bound to give you trouble

              Comment


                #8
                Good call tjc.

                Holy cow, $100 for some o-rings? That's probably what that "service" replaces. I guess if you can't do what I did then that would be the next best thing. Def. better than going to the stealership. Although I think I paid about $35 for the Exploder unit from the JY. The only issue I had was finding one that had the correct version of the ATC.
                These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

                Comment


                  #9
                  thanks tjc78 and fordman77. I finally got around to checking the vac. from the engine compartment and all the hoses and all checks out. vac pump holds good across all lines so it sounds like i am going to need some archive help and model and years of explorers. This would be a whole lot of help so thanks in advance for the help.

                  Comment


                    #10
                    Let me dig into my info and find it. Might take me a day or so as I'm working late most of this week. I have the Explorer head at home in the garage so I can get the Ford part # off of it.
                    These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

                    Comment


                      #11
                      Fordman77, I was able to rebuild the solenoids like you suggest and it worked great. It was easy to do also. Thanks for the help. I should have replied sooner but I've been real busy and dont drive the car as much anymore.

                      Comment


                        #12
                        No problem. I know how much of a PITA HVAC and electrical gremlins can be. Before the ATC issue in my car, I had the LCM shutting the headlights OFF at random times. Not good on a dark country road. Only way my wife had headlights when it did this was to hold the flash-to-pass down, but then of course you're blinding oncoming traffic, lol... Ordered me a new upgraded resistor and desoldered/resoldered it onto the LCM and it's been fine ever since. I actually bought 2 of them so I would have a spare.
                        These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

                        Comment


                          #13
                          Yep, My lcm is now causing my lights to come on and off. Also my windshield wipers are acting stupid also.

                          Comment


                            #14
                            I like you guys with newer cars that have stupid problems. Makes me realize that if I bought a newer car, I'd still have the same crap to fix. Nice to know they kept the same sort of "features" across the platform for a lot of years, HVAC whackiness, lighting nonsense, electrical gremlins. That must really take some design talent. Completely re-work the system so its nothing like what it replaces, but still have it screw up in a similar retarded manner.
                            86 Lincoln Town Car (Galactica).
                            5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                            91 Lincoln Mark VII LSC grandpa spec white and cranberry

                            1984 Lincoln Continental TurboDiesel - rolls coal

                            Originally posted by phayzer5
                            I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                            Comment


                              #15
                              dont know if you fixed the ac issue but does the check engine ligh come on? it might not but if you experience a surge when you are driving the car it is the blend door actuator. i have the issue right now. there are posts on you tube on how to change it but it looks like a real pain in the ass. i got a quote to get it done for 475.00. the actual part is cheap if you do it yourself

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