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My 2005 pacifica 3.5 AC will only come on If I turn the defrost on the compressor runs then it only blows amb. temp air.
With the compressor running the press are low 25-30 high climbs to 250. When the cooling fans come press drops to low 8 high 105.No compressor run unless the defrost is on. Reg cooling no compressor run. What could the prob be??
With low side dropping to 8 you have a low charge and the low pressure switch disabled the a/c. Put some uv dye in system and a partial charge till pressures stay above 30 on low side when running. then run system for a day and then take a uv light with yellow uv leak glasses and look for the leak. Checking at fittings, stv valve, condensor, compressor (front, sides, line connections,and rear) a/c lines, service ports, reciever drier to find leak. Or you can use real soapy water and spray it at the same points and watch for a while looking for bubbles to show. The only component not viewable is the evaporator under dash in the hvac unit
Once you find the leak or leaks mark them with grease pen and have system evacuated then replace seals or orings or component and reassemble to torque specs, vac the system to 30 inches hg for 30 min then let system set for 15 min to see if you loose vacuum (neg pressure test) of no loss of vacuum then partial charge system and check for leaks if none then fill system to spec and check output of center duct with thermometer making sure a/c blows cold ~39 degrees full cold on recirculation. If does then your done
Oh you will need to change out the receiver drier/ accumulator (aka big aluminum tank thingy since low side is dropping that low may have moisture inside it )
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