AC
07-16-2013, 12:38 AM
#2
Rennlist Member
How soon after turning it on, and how frequently does it cycle? Could be a number of things. Since you know there is ample freon in the system, try bridging the low pressure switch and see if stays on. If it does you may have a faulty low pressure switch. Could be the freeze switch kicks it off based on evaporator temp. Probably numerous other possibilities as well. Others will most likely have additional suggestions.
07-16-2013, 01:17 AM
#3
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Pressure gauge readings might help.
In the meanwhile:
Was the system empty when you put the 30 ounces of R-134a in?
If the system was empty, was it evacuated (vacuum pump) and the receiver/drier replaced)?
Has the system been correctly converted to R-134a? (Correct o-ring seals, correct oil in the system, correct expansion valves, correct drier, at minimum?)
If the system was in fact empty but not evacuated (all the air removed with a vacuum pump) adequately, the air in the system will screw up the expansion valve and reduce performance significantly.
If the system was evacuated and it is not a rear-air car, the charge is about right. If it is a rear-air car, you are about 7 ounces light on the charge.
The clutch cycles on one of three things. The most popular cause is low pressure in the system, causing the pressure safety switch to open the circuit to the compressor clutch. Same as "not enough refrigerant" in most cases. Candidate number two is a failing compressor relay in the control head. Three is a freeze switch that's working correctly, opening when evaporator temp drops below 35ºF so it doesn't ice up.
You didn't mention whether the vents are cold when the compressor runs, or how long it runs initially before the cycling starts.
In the meanwhile:
Was the system empty when you put the 30 ounces of R-134a in?
If the system was empty, was it evacuated (vacuum pump) and the receiver/drier replaced)?
Has the system been correctly converted to R-134a? (Correct o-ring seals, correct oil in the system, correct expansion valves, correct drier, at minimum?)
If the system was in fact empty but not evacuated (all the air removed with a vacuum pump) adequately, the air in the system will screw up the expansion valve and reduce performance significantly.
If the system was evacuated and it is not a rear-air car, the charge is about right. If it is a rear-air car, you are about 7 ounces light on the charge.
The clutch cycles on one of three things. The most popular cause is low pressure in the system, causing the pressure safety switch to open the circuit to the compressor clutch. Same as "not enough refrigerant" in most cases. Candidate number two is a failing compressor relay in the control head. Three is a freeze switch that's working correctly, opening when evaporator temp drops below 35ºF so it doesn't ice up.
You didn't mention whether the vents are cold when the compressor runs, or how long it runs initially before the cycling starts.
