Auto Air Conditioning & Heater Repair: auto A/C pressures, infrared thermometer, precise diagnosis

Question
QUESTION: The pressure on the Low side reads 100 on the test gauge. My service person said that means that the system is leaking from the High side to the Low side causing the high reading.  He will have to put dye into the system to find the leak.  It seems to me that if it is leaking from high to low that it would be internal and not detectable from the outside.  What do you think? And what would you do next?  Thank you.

ANSWER: Hey Warren,

  Your right, a leak detection dye wouldn’t help if it is an internal leak. With that said I don’t think I have ever heard of an internal leak before, what it sounds like is a restriction on the low causing a high reading on the gauge. What I would do next is have the service tech check for a restriction on the low side of the system.



---------- FOLLOW-UP ----------

QUESTION: Thank you.
I assume then, that the system will have to be emptied and tested. So that it is nothing I can do.  Correct?  Thanks again.  It makes sense.  That is what I like.     warren

Answer
The refrigerant will have to be evacuated in the event of a repair made on the system but that is after a complete and precise diagnosis. You could try to find the restriction yourself but you would have to get an infrared thermometer to find the spot where it is the coldest (that’s the sign of a restriction) and that just might be under the dash board. So if you don’t have a lot of experience with a/c system diagnosis its better left to the repair shop.