A/C Temp varies w/ RPM

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  #1  
Old 09-03-03, 06:41 PM
jpennington43
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Question A/C Temp varies w/ RPM

What causes my A/C temp to be colder at a high rpm than at idle? My 1995 Chev 1500 p/u truck has started doing this to the point that hold higher rpms at traffic lights just to keep comfortable. Freon?, pressure switch?...??????
Thanks!
jp
 
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Old 09-03-03, 06:55 PM
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A/C Vent temps will always be cooler at higher rpms, and highway speeds. If you are getting warm air at stop lights then you may have a low freon condition. Thats not the only possibility but most likely you are aclimating yourself to the cool temps while at higher speeds and when you idle the air gets warmer and you assume there is a problem. Get yourself a thermometer and stick it in the center vent ( should be the coolest) while sitting in your driveway with the A/C running at idle speed. If you have it in there right you should get at least 42-45 degree vent temps with a full charge and everything functioning properly. Some folks may say these temps will be different numbers but that is what I have seen in my experience. Also your climate and humidity will factor in to these readings.
Hope this helps ya,
Billy
 
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Old 09-03-03, 07:13 PM
jpennington43
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Thanks Billy... and from a local guy! I'll do the temp check w/ a thermometer.

-jp
 
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Old 09-03-03, 07:23 PM
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JP...... Thats cool. I didnt even see where you were. LOL
Billy
 
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Old 09-03-03, 09:06 PM
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As he said the temps will vary. I do not remember many that will be much below 50 degrees at idle. Also you will find the temp to be coldest on low fan speed and warmest on high fan speed. The coldest temps will be seen when set to max or recirculate.
 
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Old 09-04-03, 04:33 AM
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Any time I am doing A/C work, checks or repairs, I set the fan to the setting just below high, which is usually 3. This gets the coldest idle vent temps. I have seen 34 degree vent temps at idle. This was in my own truck however . I have seen very low vent temps as idle, but as i said before you have to have a full charge and everything has to be in proper working order.
Billy
 
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Old 09-04-03, 06:44 AM
Joe_F
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Yea, depends on the system. Some cars are meat lockers even at idle (shivers as he thinks about his own cars..lol).

Actually, it's COLDER at the lower fan speeds. That's because there is less of load across the evaporator. .
 
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