A/C Issue

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D

DieselDawg

10 Year
Joined
Jun 23, 2013
Threads
1
Messages
4
Location
Atlanta, GA
We took our 03' LC on vacation and we had a small A/C problem. The air conditioner wold work great for the first 30 minutes of driving or as long as the outside temperature was below 84 degrees. We noticed that after 30 minutes or if the OAT was above 84 degrees that the A/C still worked but not as well as it should. The compressor was still running but the air from the vents was not nearly as cold as it should be. I cycled the temperature control and also shut the A/C system off and then back on. Nothing seemed to make the system blow as cold as it should. I disconnected the ambient temperature sensor and the plug under the freon sight glass and cleaned the connections with contact cleaner. I also observed the freon in the sight glass while the A/C system was running. According to the service manual, the sight glass says that the freon level is at or near correct and flowing correctly. I drove the LC around after our vacation on a day that was hotter than 84 degrees and the A/C worked correctly for the entire 45 minute trip. I am confused as to what might be the problem with our A/C. I hope that someone on this board might be able to offer some insight into this issue. I refuse to take the shotgun approach with parts on this vehicle, as this can get expensive and time consuming.

Thanks,
Matt
 
Mixer motor going bad? With the engine off, can you cycle the output from heater to defrost? Does it sound smooth or can you hear it hang?
 
X2 Air mix servo, the servo motor which operates the hot/cold flap, it mixes hot air with cold to keep the correct temp in the car. When you run you a/c on AUTO, it constantly adjusts to make the correct setting, to fix it it requires the entire dash to be removed to get to the back of the air box to replace the actuator. If you sit in a quiet garage, ign on, turn the a/c to MANUAL, and adjust the air temp slowly and see if you can here the motor move and stop each time you move the dial a bit, if it keeps going the gears are probably chewed. Hope this is not it, but likely that it is. I haven't heard a chewed one, just diagnosed from afar, I believe you may be able to use a mirror to watch the flap movement to confirm operation, but have not done this myself.
 
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Thank you for the replies. I will look into the air mix servo this afternoon. As far as the A/C settings go, I never run the system in "auto". I think tonight I will look at the ambient temperature switch again. I seem to remember something in the service manual about using a multimeter to check the switch.

My wife did drive around town again today for a couple of hours. There were multiple stops and starts of the engine and A/C system. She told me that the A/C system worked fine and blew frigid air the entire time she was driving. She also told me that the outside air temperature never got above 82 degrees.

Thanks,
Matt
 
Even in manual, the air mix servo is controlling temp. Auto only adds location and fan speed. In the 100 you don't control the door position directly, only the desired temp and it does the rest. The exception should be at Max Hot (85) or Max Cold (65) where the door should hit the stop regardless of what the temp sensor is doing. At least that's the case with the 2000, YMMV on the 2003.

If it was just the one trip, I suppose it could have been a bit of debris that was blocking temporarily and was released.
 
If the air mix servo controls the temperature, what tells the servo to change the position of the door? This could possibly be my issue? I am thinking that the servo is told to adjust for a very cool temperature by adding some heat. After the temperature raises in the cabin the servo never re-adjusts by reducing the heat being mixed in with the conditioned air. Am I off base with this theory?

Thanks,
Matt
 
DieselDawg said:
If the air mix servo controls the temperature, what tells the servo to change the position of the door? This could possibly be my issue? I am thinking that the servo is told to adjust for a very cool temperature by adding some heat. After the temperature raises in the cabin the servo never re-adjusts by reducing the heat being mixed in with the conditioned air. Am I off base with this theory?

Thanks,
Matt
Click to expand...

Have you checked the cabin air temp sensor is not gunked up with fluff and dust and that its pilot tube is still connected?

Sent from my iPhone using IH8MUD
 
PADDO said:
Have you checked the cabin air temp sensor is not gunked up with fluff and dust and that its pilot tube is still connected?

Sent from my iPhone using IH8MUD
Click to expand...

^ This is another good check. In the OP, he said that he checked the ambient sensor. I'd assumed he meant cabin, not grill.

There are two cabin sensors, one overhead between rows 2 and 3, and one by your right knee. The later controls temp up front. It is not uncommon for lint to block or for the corrugated plastic hose to come off. It does draw a slight suction to pull air across the element, so if the hose is off so will your temp. Although, I can't believe it would think it were cooler than expected so I'm leaning back toward the air mix servo.
 
I cycled the vent settings from floor to defrost and back to the upper body position. The servo worked great. I performed this check with the engine off and in a quiet garage. I also cycled the temperature control from max cold to max hot and back to max cold. I noticed that the flapper inside the drives side vent would close completely at max hot and then open completely at max cold. I also did a little driving today and I noticed that the air in the passenger rows is also not very cold. Once again the system worked great for about 30 minutes and then it begins to blow cool but not cold air.

The ambient temperature sensor that I checked was behind the front bumper. What is the exact location of the forward interior temperature sensor? Can I disconnect a wire harness from the air mix servo to see if the A/C will blow cold after 30 minutes and with outside air temps above 84 degrees?

Thanks,
Matt
 
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