Is a refrigerant leak around the Schrader valve "normal"?

Inside heat pump evaporator coils freezing up. Tech came out said unit low on refrigerant and added 1 1/2 pounds. Worked a day and a half started freezing up again. Called same company, same tech came out did somewhat of a leak test. Checked the inside evaporator coils, no indication of leak with the electronic tester or soap bubbles. Checked outside condensing unit same methods, assumed it was somewhere inside the sealed coil unit, recommended replacing outdoor unit. His electronic sniffer never went off, I was there. No visible oil residues. Talked to office trying to give me a quote on unit, told him not satisfied leak was pinpointed. Said he would send out another tech. This guy came, said outside not leaking, but when he had the electronic sniffer around the Schrader valves it went off. He said some leakage there was normal. Then checked my inside evaporator coils and said it is a coil behind the tin. Recommends a new evaporator coil unit inside.
Unit is 11 years old. Only problem before now was capacitor when under warranty when a couple years old.
Questions are? Is leakage around Schrader valve "normal"? after reading some online, I've learned now after the fact, they should have done a leak test and never added the freon until leak was repaired. Any advice would be appreciated.
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Jon wrote:

I can tell you this, I had a leak and I spent a lot of money and time only to discover the leak was at the Schrader valve. I felt the tech should have checked it from the start, but that would have reduced his income. When it was discovered where it was leaking, I got an "O" ring and placed it under the cap over the valve. I never had a problem after that.
There probably are some HVAC techs out there that are competent and honest, but you really need to hunt for them. One more story:
When I first moved into my home which was just built, I had one of my AC condenser units fail to start one day. Since it had been installed less than one year at that point, I called the company that had installed it. The tech came out and approached the condenser unit without taking out a voltmeter, and said I needed a new condenser unit. To which I said, "Go ahead replace it, it should be under warranty." He said the unit was, but the labor was not, and I must pay that. Since my field is electronics and I could not believe he made a diagnosis without even establishing that power existed, I told him I would think about it and call him back.
Five minutes after he left I had the unit running. The leads from the thermostat were twisted to those for the contactor and wrapped with tape. I soldered the leads and the unit ran for another 30 years!!!
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On Tuesday, July 28, 2015 at 7:34:03 AM UTC-4, Ken wrote:

Had similar issue with A/C not starting, service guru wanted to replace the control board. I just tightened the thermostat connections to the control panel and have never had another problem.
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"Ken" wrote in message
Jon wrote:

It depend were the Access Schrader is located but you should always check when you are done servicing system, it is also available Bonny caps that are made all out of brass and if install properly no not likely it will leak.
I can tell you this, I had a leak and I spent a lot of money and time only to discover the leak was at the Schrader valve. I felt the tech should have checked it from the start, but that would have reduced his income. When it was discovered where it was leaking, I got an "O" ring and placed it under the cap over the valve. I never had a problem after that.
There probably are some HVAC techs out there that are competent and honest, but you really need to hunt for them. One more story:
When I first moved into my home which was just built, I had one of my AC condenser units fail to start one day. Since it had been installed less than one year at that point, I called the company that had installed it. The tech came out and approached the condenser unit without taking out a voltmeter, and said I needed a new condenser unit. To which I said, "Go ahead replace it, it should be under warranty." He said the unit was, but the labor was not, and I must pay that. Since my field is electronics and I could not believe he made a diagnosis without even establishing that power existed, I told him I would think about it and call him back.
Five minutes after he left I had the unit running. The leads from the thermostat were twisted to those for the contactor and wrapped with tape. I soldered the leads and the unit ran for another 30 years!!!
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On Monday, July 27, 2015 at 9:44:02 PM UTC-4, Jon wrote:

Get some brass caps for them is the easiest fix. Leaks can be hard to find if they are small. I had a unit that leaked about 1/2 lb a year, finally found the inside coil was the culprit but only after the leak got worse.
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wrote in message
On Monday, July 27, 2015 at 9:44:02 PM UTC-4, Jon wrote:

Get some brass caps for them is the easiest fix. Leaks can be hard to find if they are small. I had a unit that leaked about 1/2 lb a year, finally found the inside coil was the culprit but only after the leak got worse.
**The gentlemen above is absolutely right use of brass cap can solve problem if that is where leak is. Lot of electronic detectors or good and no good Mechanic must know to use it right way, and some time must increase pressure to do reliable right check.**

liquid soap not one that is use in dishwasher but hand type diluted one part liquid soap three parts water, you may need full bucket pending size of your condenser and purred all over and I mean allover. make sure your power is off, if is leaking some place it should show bubbles some place. When you done take hose and rinsed off with clean water.<<<<<
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On 10/26/2015 2:10 PM, tony944 wrote:

Did you look at the date on this original post..July!!

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Has anyone looked at the airflow across the evaporator coil. Low air flow across the evaporator coil can cause a coil to frosted up and look like the refrigerant charge is low too
Jobarco.
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