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Old 07/05/2017, 01:59 PM   #1
hatchdog's Avatar

Location: Spokane, WA
Joined: May 17
Posts: 117

Air conditioning question

Greetings all,

Yesterday I drove my car to the Post Falls, Idaho area which is about an hour from my home. I left early in the morning when the outside temps were still cool but drove home mid-afternoon in 90* heat. I drove on a highway at 55 mph and lower. As I expected to use the A/C I put a thermometer in the center dash duct to measure the A/C temp.

While driving at 55mph the temp on the thermo read 60* and the air felt cool but not ice cold as in my modern car. At no time did the cabin of the car feel like it was cooling off and remained somewhat uncomfortable the entire time. Part way home I was stopped by a train. I put the car in park and left the engine and A/C running as I was curious what would happen. The temp on the thermo raised to 70* and the cabin was even warmer.

The A/C on my car is all new components and is the new R 134 freon compressor. At no time did my temperature gauge show any sign of overheating.

I have done a bit of internet research and read that the best one can expect is for the air from the ducts to be 25* less than the outside air but I'm not sure if this was with R12 or R134. If this is the case having my duct air 30* less than outside should be good. I also read that while the car is not moving, as in waiting for the train, the lack of air over the condenser will cause the A/C temp to raise.

So, after the above long short story, is it your opinion that my A/C is working as well as can be expected from a 49 year old car or should I have it looked at?

Also, just to make sure I am operating the dash controls correctly, I set the left switch to max, the center to cool of course and the fan to various speeds. Before I left I checked the system with the hood open and it sounded like the compressor kicked in when I turned the on fan switch. Does it sound like I am setting the controls correctly?

Thanks for your input, it's just gonna get hotter here in Eastern Washington State.

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Old 07/05/2017, 04:01 PM   #2
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Location: Franklin, NC
Joined: Mar 07
Posts: 4,123

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Hmm. Everything in the A/C system is new: Compressor, Drier, Condensor (oversize), Expansion Valve, Hoses, R-134 Freon. I flushed & evacuated the evaporator prior to installing all components.
After evacuating the system and verifying no leakage, charged with R-134.
Outside temp was 80/85 degrees, air temp out of the center register was 50 degrees. Not great, but within prescribed range.
There are 4 possibilities, listing the least in order:
1.) Vacuum control rubber tubing (All new. I checked & rechecked operation of the vacuum operation, all checked OK).

2.) 35 degree sensor mounted on the Evaporator: It prevents the Evaporator from icing. If the evaporator gets too cold and forms ice, the sensor opens the power to the Compressor clutch, turning the Compressor off. Since you say the compressor was running, this would eliminate the sensor.

3.) Hot (heated) air mixing with cold air from the evaporator inside the Heat/AC box under the dash. The doors/deflectors appeared to be working properly when I checked. If you block the hot water hoses to the heater, preventing the heater core from getting heat, and cooling improves, then I would suspect the 'mixing' deflectors are not working correctly. If no change or improvement in cooling, then the most probable cause would be:

4.) Expansion Valve. Although new- this is my guess as to being the culprit. When the A/C installation was completed I added 24 ounces of R-134 as per instructions. My gage readings (Lo side, High side) were 20 on the Lo, 175 on the High side. These readings were dead center of desired pressures.
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Old 07/06/2017, 06:51 AM   #3
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Location: Spokane, WA
Joined: May 17
Posts: 117

Morning Neil,

Thanks for your input. Your suggestion #3 reminded me that many years ago I bought a used car from the local Ford dealer and the A/C wasn't getting cold. I took the car back to the dealer and they discovered that the hot/cold switch was binding and allowing heated air to mix with the cold. All it took was a firmer push on the switch and the problem was gone.

It does seem that when I push the control up to cold it wants to drop down towards warm a little bit. I will remove and plug the heater hoses as you suggested and test this theory.

Thanks for your in depth response to my post and always know we are thrilled with the car. Hey, it's 49 years old, things are going to happen. I drove it to a golf course in Post Falls after stopping to pick up my cousin. We then met two guys we worked with and I had the pleasure of showing them my car. However, I did have to remove the spare to fit two sets of golf clubs in the trunk.
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Old 08/09/2017, 01:32 PM   #4
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Location: Spokane, WA
Joined: May 17
Posts: 117

Still working on this issue, Arlie took a look at my car and thinks the heater control valve might be defective. He felt the outlet side of the valve and it was very hot and should be cold. I picked up a infrared thermometer and I got readings nearly the same (140*) on both the inlet and the outlet with the A/C controls set to max. I checked the vacuum and the line is pulling 16 inches which from my reading is fine. I just now ordered a new Scott Drake valve and hopefully this will fix my problem. Neil replaced this valve when he rebuilt the A/C system but I also have read that they can be temperamental (pun intended)
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