Engine Size: 350/5.7
Refrigerant Type: 134a
Ambient Temp: 100
Pressure Low: 05
Pressure High: 200
Country of Origin: United States
Hi all, I have a 98 GMC 1500, The A/C blows cool but not cold it doesn't seem to have any leaks.
When I connect the gauges it shows 200 on the high side and 5-8 on the low side.
The compressor never cycles it just stays on, if I unplug the low pressure switch it will turn off
but if I unplug the high pressure switch there is no change.
Any ideas welcome.
Phoenix AZ about 90 to 100 outside
The low side pressure is TOO low . The high side sounds too high to go with the low side pressure . But I may be wrong ?
Did you say if the radiator cooling fan is working ( mechanical or electrical ? ) ?
Is the condensor stopped up with leabes , bugs , trash ?
Is the engine over heating ?
Do not know if you have an expansion valve or orifice tube system ? Guessing , orifice tube . And wondering if it is stopped up ?
Were it me , I would try to trace the high pressure line / liquid line to the point where it is goung into the evaporator / cab of the truck . Is it cool or cold at all ? If it is , try working your way back the other way , towards the condensor coil . Does it transition from cool / cold to warm / hot ?
If so , at that spot , are there a couple of fittings there ? If so , thet is most likely where the orifice tube is located .
If it transitions where there is no fitting , you may / probably have a restriction there ?
Not being there , I would have to take baby steps . And proceed , acording to the information that was discovered .
better get a new cycling switch-- yours is stuck shut- should go off at 21-22 psi and on at 42 psi.....continued running at low suction decreases oil flow and burns up compressors...
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
In a car , the engine RPM is constantly changing , while you are driving . This constantly changes the compressor RPM .
The air flow over the condenser changes from what the fans can provide , to much more than that when you are driving at highway cruising speeds .
With all the glass surrounding a car interior , the heat load varies a lot . And there is not a tremendous amount of thermal insulation separating the driver and passengers from the outside environment .
None of these situations apply to stationary HVAC . Or , at least not as much . Not at all , when considering the variable RPM and condenser air flow .
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