Please help, I have a 2007 ford five hundred with 60,000 miles, out of warranty. I am having a/c problems. As long as the engine is revving at about 2000 rpm or the car is being driven the a/c cools fine. At idle for any length of time the a/c starts to warm up and gets progressively warmer the longer you sit. To the point it seems it doesnt cool anymore. It warms instantly so I dont think something is froze up, and when I drive it instantly cools down. I have recently had the expansion valve replaced and the system charged, this did not help. The shop were I took it to is aware it did not work, I just have to wait a day or two for the weather to warm back up again and have them take another look at it. They seem just as puzzeled as I am. Any ideas?
You can be blunt or you can bring them some basic AC system diagnosis textbooks.
If the compressor is working correctly the problem may be the “blend door” in the HVAC system. The blend door controls interior temperature by sending incoming air through either the heater core or the AC evaporator (or both) depending on the desired temperature.
If the blend door is vacuum controlled it could do exactly what you describe, since vacuum is high at idle and drops off as you open the throttle. At idle the blend door may start moving and direct airflow more and more towards the heater core. When you open the throttle the blend door moves back toward the AC evaporator.
A vacuum leak would explain this, assuming the system is vacuum operated.
Why was the expansion valve replaced?
Blend air door is electric in this car.
Well, there goes that theory.
mcparadise thanks for your response, I failed to mention that it seems the air temp on the right side of the car feels slightly warmer than the left side vents when this happens. The expansion valve was replaced, and I will state what was typed on my invoice, “performed a/c perfomance test, ambiant temp @80 degrees. Duct temp @70degrees. Hooked up gauges and found low side pressure was 60psi and high side pressure at 120psi. Expansion valve stuck open. Need to replace expansion valve, evacuate and recharge system.” This was done, unfortunately we had a cold front come through as this was being performed and the outside ambiant temp dropped into the upper 40’s and the tech was unable to check if this worked. Yesterday it was back into the mid-80’s and could tell that it didnt. I am dropping the car back off tonight to have it looked at tommorow, tommorow in D/FW it is supposed to be 65 degrees so we will see.
I have been researching and I guess Fords are known for blend door failures, even the electronic ones. Two questions, Does anyone know were the blend door is located on my vehicle? It seems that most accessories (blower motor and various swithes) are faily easy to reach behind glove compartment and in passenger compartment? Would the compressor be bad if it works at anything above idle?
Can you always get hot air out when you set the control to hot? Does it then always return to cooler air when you set it to cold? If so, it is probably not the blend air door. If you have auto climate control, then there is a diagnostic test that you can run from the control head to verify the blend air door operation.
My theory is that the compressor is not pumping enough, and that is why the mechanic was fooled into replacing the expansion valve. The faster the engine speed, the more the compressor will pump. Another thing to check is the engine cooling fan. It should be at full speed at idle with the AC on.
How are the pressures looking now?
Yes, I can always get hot air when I set it to hot and it does always get cooler when I go colder. I do have auto climate control, is the diagnostic test something I can do myself or just the dealer? I dont know what my pressures are at this time, (no gauges). I did find a TSB for 2005-2006 five hundreds #19107, mine is an 2007, for noise in the passenger compartment-air inlet door inoperative (recirculation). Could this possibly explain my problem? Are TSB’s handled at Ford’s expense? or are they just guidelines for the tech to work on. If I would still have to pay, I would try to put it on myself. I called the dealership and the door actuator is only $33.00, I would try to put it on myself if I knew were it is, anyone know?
TSB’s are guidance, you need a pressure check. With both high side high and low side high this can indicate a “flooded” evaporator which can indicate a defective expansion valve. I can’t fault them for replacing the expansion valve. We need to see pressures now.
It is back in the shop that replaced the expansion valve. The ambiant temp in D/FW today is only going to be around 70 degrees, so this might hurt them in diagnosing the problem. I will keep you posted.
Before making much of a guess at this I would need to know what the high and low side pressures are; preferably at elevated RPMs. (1500-2000)
I’m a bit surprised that Ford used an expansion valve on this car. Thought that Ford pretty much went the orifice tube route on everything starting over 20 years ago. ???
My Lincoln LS’s use expansion valves. I can find other recent Ford examples too.
Back from the shop, after a day and a half unable to diagnose the problem. Outside ambiant tempatures in the mid 60’s by afternoon is not hot enough to cause a big need for a/c. Will take it back in about a week when temp’s are to be warmer.
I have this same problem on a 2005 Five Hundred, I was assuming it was just low on Freon and was ready to recharge it today but the fill valve is almost impossible to get to…I came online trying to get ideas on how to do this when I stumbled across this post…now I am concerned that it may not be low and I have a bad compressor. I am in Florida and need A/C, it cools fine while driving but at idle it immediately gets warm.
I still have not had mine fixed, I live in the D/FW area and it has not been consistently in the 80’s yet to have them diagnose it. Unfortunately here it will go from mild to 90’s in a couple of days. I originally took mine to a independent a/c repair that has been around since the 1960’s with the same owner. He hooked gauges up and spent about 10 minutes with my car and diagnosed it with a bad compressor, 2 days, $1000.00 dollars and lots of work on his part. He didnt seem too excited to tear into my car and I wasnt too excited to spend $1000.00 without a second opinion. That is when I took it to the place above that diagnosed a bad expansion valve, and $286.00 dollars so I was happy to pay this. This did not fix the problem. I am back at square one, waiting on the temp’s to get warm. In my post above I found TSB #19107, have you had the dealer look at this as a potential cause to your problem? It covers your year model. Have you done lots of idling in your car since you have had it? I have, I am in sales and when I am on the phone and writing I always pull over (lots of times with temps in the upper 90’s to 100). Someone told me that idling for extended periods of time is suicide for an a/c compressor. Have you had yours in the shop at all? What did they say?
Now you have crossed the line, the ambient temp does not have to be in, what are you saying mid-80"s for diag. Never heard the “extended idle” warning. I do know that life is tough for a AC compressor.
oldschool, I get what your saying about the temps. Only thing I can say is that when I have taken it in once for the expansion valve diagnosis it was 80 at diagnosis and in the mid 40’s when I picked it up, unable to tell if that worked until it warmed up. Dropped it back off at the shop for second time and it was 82 at drop off, cold front came through that night and it did not get out of the 50’s as the high and upper 30’s for lows for 3 days. I was told that since the electronic temp control only goes down to 60, that the computer was not calling for a demand for a/c since the temp in the car was already colder than 60, therefor the mechanic or myself could not tell whether the a/c was warming up or not since it was cold outside. Whether this is correct or not, I dont know. I am going on what the tech said, but I dont need my a/c when I have the heat on.