2002 Dodge Dakota (factory air)
Recently I've noticed a reduction of cooling (max low 56 degrees on a 90+ day So. CA) and a knocking sound coming from up near the evaporator or maybe at the bulkhead(I think that is near where the OT is). This sound happens only when the compressor is engaged. Could this be a sign of a clogged OT? The truck has 200k+ on it and I don't think anything has ever been changed.
I evac'd the system and recharged it with the correct weight of R134 +oil but the noise is still there.
Thanks for any comments
Knocking sound near orifice tube location
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JohnHere
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Re: Knocking sound near orifice tube location
When you recharged it, did you put in the full amount of oil?
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JohnHere
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Re: Knocking sound near orifice tube location
The specs for your vehicle call for 32 ounces net weight of R-134a and 7 fluid ounces of PAG-100.
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Re: Knocking sound near orifice tube location
As compressors age they get louder as parts wear. Luckily as people age our hearing gets worse. 
OT can make hissing or gurgling sounds, knocking is the compressor not the OT
OT can make hissing or gurgling sounds, knocking is the compressor not the OT