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evap temps

joe_mn on Mon June 24, 2013 8:10 AM User is offline

Year: 1996
Make: cadillac
Model: seville

car in 70f garage. put temp probe on evap outlet line. back out to driveway. 82f ambient. start a/c get 35f evap temp. take another temp measurement from dash vents. get about 55f dash temps. after several minutes i go back to engine area and check evap outlet and now it is about 50f. back to dash and its still 55f. was the low 35f initial evap temp due to the car being in cool garage to start with and now it has warmed up due to hot engine bay? i dont think 55f dash temp is good enough for me.

iceman2555 on Mon June 24, 2013 10:04 AM User is offlineView users profile

First it must be determined if the system is properly recharged. This should be done utilizing the correct equipment...not cans and a manifold/gauge. Have this professionally done.
At this time recheck temps and AC performance. A evap outlet of 50 degrees would suggest a vent temp similar to your post. Could the difference in ambient temps effect the system in this manner....yes, they could.
Get the system serviced and then re evaluate your performance concerns.

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Thomas Jefferson

joe_mn on Tue June 25, 2013 8:11 AM User is offline

did a startup procedure again. than i realized the evap outlet 35f is with interior blower fan at low speed. once i turn on fan to high, the evap outlet rises to 50f which is expected. you are removing heat from cabin and raising freon temp exiting evap. i than set fan speed to low again and the evap temp dropped down to 37f or so.

mk378 on Tue June 25, 2013 10:10 AM User is offline

This appears to be a CCOT system which means that by design, when properly charged, the evaporator "floods" with liquid refrigerant. This causes the evaporator output line to be the same temperature or slightly colder than the input line. So you should accurately measure both line temperatures, and if the output is warming up more than the input does, it is likely undercharged and should be evacuated and recharged by weight.

It could be normal. Even a Cadillac is still subject to the laws of physics, and very few cars are overbuilt enough to hold a 40 degree vent temperature at idle with high fan in hot weather.

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