HVAC worked on 1200 BTU unit

We had Mike from "Rescue Refrigeration" come by and charge our 12000 btu unit. We want to fix this unit once-and-for-all because it is now the last broken item on the boat. Our 5200 unit in the stateroom works great and the fix for it was replacing the Schrader valves which they did at the factory before we left on the Baja Ha Ha in 2012. We called and talked to Mermaid again and after some more emails we found out that only the Schrader valves needed to be replaced.  We had always thought that the Schrader valve stems had to be replaced also and that was a big job.
Schrader  valve replacement tools below.
June 2016 - Tied up in Marina Mazatlan, Mexico


Schrader valves and holders (stems).
So if we just need to replace the Schrader valves that makes life way easier. Mermaid said that they were 99% sure that is what is leaking. So we decided to purchase the Schrader valve replacement tool and do it ourselves. One reason is that Mike from "Rescue Refrigeration" estimate is way high and we can save a lot of cash by doing this simple job ourselves. Even factoring in the cost of the tool we will save some good cash. 
 We then found out there are two sizes of the C & D tool. We called a refrigeration parts shop but they only sold wholesale. They also wanted us to be Certified to even size up the the tools. Ok back in the US we are, with all the regulations etc :). 
We went to a HVAC forum (HVACTALK) and asked the Schrader tool size question.

And the answer is:
"5/16 is for 410A/R32 rated high pressure equipment, 1/4 for everything else.
 5/16 fittings are manufactured so you can't mistakenly fit lower pressure rated equipment which has 1/4 fittings." 
So because the Mermaid 12000 we have has R417-A the tool size would be 1\4.
We found a C&D Valve CD3930 1/4" Ball Valve Core Removal Tool for $50.00 on Amazon and eBay. We purchased one.with no-questions-asked on eBay.  Let you know when we actually replace the valves and re-charge the unit up.
Two Schrader valve with covers on them - the unit out and 
hot water heater near by when unit back in.
Just the Schrader valve holders. 
This is like replacing an air valve in a valve stem on a bycycle inner tube. You screw the tool onto the valve stem and then you can replace the stem inside the without loosing air (example).
Mermaid said if for some reason the new valves 
do not fix it then we need to replace the holders also.
R417-A 


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