It may be time to get another electronic leak tester and I'm looking for what others use. The TIF 5500 I've used for years never seemed to really work right and now is worse. It will find a gross leak ( like loosening a charge hose ) but regular leaks are a challenge. Now getting non repeatable results, random beeping. Changed tip no real difference.

I have access to a ultrasonic leak tester that I might give a try, any luck with those or are they more suited to gross compressed air system leaks?.

My 97 C280 will drop pressure from 45 PSI to 40 in 5 minutes so it is a pretty large leak,( I just pump in a bit of gas not a full charge )

The 5500 has not been able to locate the source and semi randomly beeps near the compressor area , TXV and dash vents.

With such a large leak I'm tempted to make block off plugs and isolate areas of the system. I'd rather not use freon in enough quantity to make die work until I get the big leak fixed.

Thanks