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Vacuum Pumps
Vacuum pumps are part of every A/C recharge or repair. The vacuum portion of the service is important because it removes air from the system and also removes any moisture too! (Water boils in a vacuum). But the important question is, "How much or how low does the vacuum have to be?" This information should help you better understand the importance of pump maintenance and regular vacuum pump oil changes.
An important part of your A/C Service
auto air conditioning orifice tubes and expansion valves utilize very small openings to meter the flow of freon in your system. Be sure you know how to keep these valves clean and flowing! Find out more now! Probably one of the most neglected pieces of equipment on the A/C service shop floor is the vacuum pump. Why? Because when you flip the switch, the pump turns on... and that's good enough! Not really. How well is your vacuum pump performing? Is it pulling the proper vacuum? Is it pulling 'deep vacuum'? That's what we've decided to take a closer look at.
What's deep vacuum?
You've heard the expression before... almost every A/C service manual talks about pulling 'deep vacuum'. But what's the difference? Isn't vacuum vacuum? Just the absence of air? Not according to proper A/C service procedures for recharging your A/C system.

The conventional method for measuring vacuum when servicing your A/C system is it to read the vacuum scale on the low pressure gauge (also known as a compound gauge because it provides both pressure and vacuum readings). It's a quick and usually reliable method to determine when the system is under vacuum, but what it will not tell you is a true measure of just how much vacuum you're actually pulling.

In order to get a better understanding of just how much vacuum you're actually creating, it's important to use a 'micron' vacuum gauge. A micron gauge is simply a far more accurate method of measuring vacuum.

'Microns' are a unit of measure. A micron is 1 millionth of a meter (a meter is a metric measurement equal to about 3.28 feet). In short, the micron vacuum gauge is putting the readings on a much more detailed scale that provides a more accurate reading. Using a micron vacuum gauge you can quickly see the true measure of vacuum. To better understand the differences, we've compiled a chart that compared micron vacuum readings to inches of vacuum as read on a conventional vacuum gauge. You can see those details here.

Initial Vacuum Pump test:
Before any vacuum pump service, we connect the pump directly to our micron vacuum gauge to get an accurate reading of how 'deep' a vacuum the pump is pulling.

The micron vacuum gauge is calibrated under vacuum. It's a very delicate instrument that utilizes a special coupler to convert the vacuum into an electrical current that can be read on the scale.

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:
For the purposes of our tests, we operated the vacuum pump for 10 minutes and then recorded the level of vacuum attained. This was prior to any service or vacuum pump oil change.

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.
We've completed several vacuum pump tests. You can review the details of another vacuum pump that wasn't in as good a condition.

The vacuum pump service starts:
Starting with a clean container to catch old vacuum pump oil, we drain the oil that the pump came into us with.
Although the old oil removed from the pump didn't appear all too dirty (based on color) we did find that it had debris and particles of dirt and grit. Keep in mind that this pump was pulling great vacuum when it started, and the service tech advised that 'it really didn't need a service'. Looking at the debris, we're glad we got to it!
Besides the particles of debris and grit, we did another test
on the vacuum pump oil. Have a closer look at what we found.

The rest of the service:
For this vacuum pump service, we used a new Service Kit developed to clean and improve the performance of vacuum pumps. Following the manufacturer's instructions, after draining the vacuum pump oil, we added the 'Cleaner and Conditioner'. This is a specially formulated oil that is designed to help remove varnish and lacquers from the pump as well as 'suspend' debris and contaminants. The vacuum pump is operated for a maximum of 10 minutes with the cleaning oil and then it's drained.
The rest of the service is simple. We added the 4oz. bottle of an Anti-Friction additive (included in the service kit). It's designed specially for vacuum pumps in order to provide the maximum performance and 'deep micron' readings. Following that, we just filled the pump with the new Premium Vacuum Pump Oil from the kit.

The final test for vacuum pump performance:
After refilling the vacuum pump as outlined above, we performed the same test that we did before starting any service. The pump was connected direct to our micron vacuum gauge and operated for 10 minutes. Here's a look at the results (micron gauge reading) after 10 minutes.

Vacuum pump service summary:
Overall, keep in mind that the service tech already advised that the pump was performing properly and he didn't think it required service. After draining the debris, it's a good thing we got to this pump. Although it performed well (under 200 microns) when we first started, the debris and grit can cause real problems with the 'vanes' and internal surfaces.

Overall, there was still an improvement in the vacuum pump performance. Although our 10 minute before and after test only showed an improvement of about 40 microns, it was still an improvement. Also keep in mind that this pump was pulling great vacuum to start.

Since these tests were conducted, we've done others that will be posted soon, so please check back for further tests and test results. In the meantime, take care of your vacuum pump. It's quick... easy to do... and regular service will keep your pump operating at peak performance when the heat is on!

Here's a look at another vacuum pump test and service we completed. The results after pump service were a little more dramatic!
See how the simple Polymax™ Vacuum Pump Service kit restored deep vacuum performance to this vacuum pump. At the start of our test, we were not able to pull 500 microns! See the up close results of what happend right here.

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