DIY installation of small air conditioning units

Last summer I bought and installed a small Mistral split system, after reading on this forum how easy it was. Unfortunately, it seems that I have a small leak somewhere - the unti got less efficient and finally stopped producing indoor cooling at all.
I have tried, and failed, to get a "proper" installer to vacuum (and leak test) and add refrigerant if needed. No - they insist on selling a new $1000 system and charge $770 for a complete new install.
However, vacuum pumps (advertised to suit air conditioning units) are $200 to $300 on eBay. So I am considering DIY for the maintenance. I can even buy a second unit and still come out ahead.
I would also need refrigerant, some way of measuring how much is needed - and how much I put in. And, of course, some 'how-to' do it.
Has anyone done this type of DIY job, and can give some hints on how I should proceed? What have I forgotten?

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Originally Posted by occam

Has anyone done this type of DIY job, and can give some hints on how I should proceed? What have I forgotten?

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Yes... but instead of doing a step-by-step walk-thru, how 'bout I give my bro a call first? Mt Evelyn ain't far from here. :) You'll find you need a ticket to be able to buy the refrigerant anyway. :rolleyes:

He's an ex-fridgy, now a Semi owner-driver. :eek: However, he still has all the gear and that should be a quick job. Can't say what he'd charge, but I can at least find out if he's interested and possibly arrange for you to get your heads together...

(If you're interested, 'tis probably best to PM me. Otherwise it's pot-luck as to when I check this thread again.)

You will need a set of refrigerent charging gauges documents that came with the unit will tell you what amount you need the killer part is as far as Iknoww no one will sell you refrigerent without a licence before you can get a licence you have to do training course which is only avalable post trade. if you manage to do all this the refrigerant is very expensive in the quanties that can be purchased 20lt minimum. basicly it is cheaper to get some one to do it for you, but it my experence no one is interested. dosen't help much I know. If there is another way one of the members may be able to put me straight

Mmmmm, this really seems to be a problem. I've been thinking a lot about similar issues recently. I installed a cheap "nexus" A/C in Cobar, everything went OK at the time but what if something goes wrong. The mistral packaging now is very explicit about professional fridgie and sparky hooking it up and obtaining certificates from them. I'm looking at buying 2 for a friend now. I think mistral have attracted the DIY market and paid the price for this. In the future I will engage a fridgie to vac and test for leaks.

I think these cheap A/Cs can be false economy, they are not the sort of thing you want to replace after 5 years.

Cheers
Pulse