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Vacuum Pumps
The basic unwritten rule for deep vacuum on an automotive A/C system is about 500 microns. If your vacuum pump can't pull 500 microns connected directly to a micron vacuum gauge, then there is no way it's going to perform any proper service on the A/C system before recharging with refrigerants. Here's a look at a vacuum pump that we checked and serviced. This particular pump was provided to us in what was considered 'working' condition.
The Initial Vacuum Pump test:
As we have already established, our standard test starts with a direct connection of the vacuum pump to our micron vacuum gauge. The pump is operated for 10 minutes in the exact condition that it was received, before recording the actual micron reading.

Although this pump looks a little 'worn', the technician reports that it's actually been a good pump. We just found that it was lacking some service!

Traditionally, the micron vacuum gauge would be 'spliced' into
the gauge set to confirm the vacuum reading. For the purposes
of our test, we're connecting the pump direct to the micron gauge.

After 10 minutes of vacuum pump operation:
In all of our vacuum pump tests, we operated the vacuum pump for 10 minutes in the exact condition that it was received. Then, we recorded the level of vacuum attained.

Why a micron vacuum gauge? It's the only true measure of vacuum. Have a closer look here.

As a starting point before any service, this particular vacuum
pump produced rather good results. According to the chart,
this pump is pulling in the range of 99.9% vacuum.

The vacuum pump service starts:
The vacuum pump oil drained from the pump was dark to say the least. Using a clean white container it was easy to see the residue and debris (far right) that was in this 'working' vacuum pump.
After running the Poly-Clean™ Vacuum Pump Cleaner and Conditioner through this pump, it was drained 'dirty'. It looks like the product is doing what it's supposed to do... help to remove varnish, dirt and debris from the pump.

Once the Cleaner drained from the pump, we added the 4 oz. of Poly-Protect™ Anti-Friction Additive and then refilled the pump with Poly-Vac™ Premium Vacuum Pump Oil. The complete service took about 20 minutes.

Keep in mind that this is a close up look at the Cleaner
and Conditioner that was drained after 10 minutes of operation (following manufacturer's recommendations)

The results of our service :
After refilling the vacuum pump, we connected it back to the micron vacuum gauge and operated it for 10 minutes. Following the clean up and oil change service, we were able to improve the micron vacuum reading to under 200 microns! Now we're ready to put this vacuum pump back into service!

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