Automotive AC: Any DIY priced vacuum pumps?

As I continue down the rabbit hole of getting AC on the Molvo, I just secured a crimper so that I can make my own lines and connect the various components.

Next step is going to be to verify that the system is sealed and evacuate any moisture. Traditionally done by pulling a vacuum and seeing if it holds. All I know from Vacuum pumps is from labs and those were mucho $$$$. Is there a home hobby product out there that will do the job? Can I make one from an old fridge or another AC compressor?

The next question will be around converting to 134A. I will have assembles NA Miata AC parts with a 1990 Mustang pump resulting in an R12 system. Assuming that R12 no longer exist, what is the process to convert? Is there any other options I might consider?

You'll want an HVAC vacuum pump, like the ones sold at hvacdirect.com. Mitsubishi Electric says to evacuate air conditioners to 3000, 1000, and then 500 microns of vacuum and make sure it holds at each one.

OReilly auto parts will rent you a pump for free. Gauges too.

In reply to chaparral :

never heard of vacuum units in "microns"? 

Will check out hvac direct to see how much they need for said pump.

Pretty sure this is going to end up costing the same or a bit more than having it done at a hvac shop but if I end up with tools  and enough knowledge to be dangerous, I am ahead.

I have been using a Harbor Freight pump for 10 plus years. They are pretty reasonably priced. 

Amazon had the best price on 134 the last time i bought it.

If you have a decent compressor, I've used this for 5 or 6 vehicles now with this combo, and I use it as the basis of my brake bleeder for less than 20 clams, ya can't beat it:

https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html

And having a set of guages makes all sorts of AC diagnosis way easier.  You'll be all set up for less than $80:

https://www.harborfreight.com/r134a-ac-manifold-gauge-set-58776.html

I bought mine from Amazon, right about $75 shipped.  Pulled the vacuum on my Fit and my Silverado just fine. Definitely not professional grade, but figure I might use it once a year (probably less than that) and it fits the bill. Seems about the same quality you'd rent from the auto parts stores. 

-Rob

As usual, this place delivers! Figure if I was willing to spend the $$$ to get the hose crimper, then might as well roll on the vacuum pump also. The gauges were a given. 

I will let you all know how this thing works when the time comes

Even if it all turns out that I learn not to do this myself, I will have learned something!

Edit:  basically echoing what John said.

I've used them several times. But never bought my own.

Auto Zone, Advanced and O'Reilly's will let you use their's for free through the "loan a tool" program.

Unless you really want to store it for the rest of your life, I would go that route.  I mean, how often do you really need your own vacuum pump?

I've got a Robinair vacuum pump that I picked up from Amazon something like 7 or 8 years ago.  I've used it a handful of times with good results. 

Micron vacuum measurement is standard for fixed climate control systems. Your house system is pumped down to 500 microns or lower when its evacuated.

Mobile systems are typically measured in inches of vacuum. 29 inches is the normal standard for evacuating.

I use a modest Robinair vacuum pump which I bought from Tooltopia. Not too much money at all. It falls somewhere between a Harbor Freight cheapie and a professional shop workhorse.