Ok, ran into an odd one. Typical call for a large WIF down. On roof, sight glass barely showing any refrigerant. Electronic leak check, found two leaks: One at low pressure control, other in suction line vibration absorber. Since it was in a major downpour, I gassed up for now to a full sight glass. The unit is listed at 33lbs of 404. I only had to add 5 lbs and told them I'd return.
Now, I had soaped up the vib absorber and it bubbled pretty good, but I figured it'll hold for a while until I return. But they called back the next day saying the unit was down already. Ok, I figure the vib absorber was probably leaking worse when the unit was running (checked while it was idle due to the condenser fan blowing all over). Another tech returns to complete the job, and I wind up meeting him on site after he's 90% done. He pumped down unit, changed drier, changed vib absorber and pressure control. He was in the process of adding gas. Sight glass clear after 6 lbs. Unit coming down in temp. Time to wrap up.
Then the sight glass started bubbling again. I figure the evap fans just came on, so lets add a bit more. Another 2 lbs. Ran clear - then about 10 minutes later, just as we were wrapping up AGAIN, started bubbling again. Ok, add another 2 lbs. Ran clear again, and slowly started bubbling AGAIN. So we started doing a more thorough leak check, using two electronic leak detectors and ran across every inch of tubing. I figure a leak that big should be blowing our hair back. But found nothing. It seemed we had to keep adding gas to clear the sight glass. After about an hour, and another 6 lbs, it finally started to stay clear.
Is this unusual, or common for a system with such a large receiver? Unit does have headmaster, so its possible that wasn't opening as well.