For
auto A/C service, a recommended oil change interval would be between 15 and
20 hours of operation at the most. More frequent oil changes will certainly
not harm the pump, but they may not be necessary.
The
proper interval will really depend on how you use your vacuum pump. As an
example, you can complete a very quick test right now by checking the oil
level on your vacuum pump with a UV light. If the UV light actually fluoresces
the oil in the vacuum pump, then you have UV dye in the vacuum pump oil,
and that is a serious contaminant that should be removed.
After
extensive work with vacuum pumps, we have found countless pumps that suffer
from sever sludge build up and even have particles of o-rings, gaskets and
other debris mixed with the oil. It’s clear that in a lot of cases,
the vacuum pump is being used more as a vacuum cleaner.
The
sole purpose of the vacuum pump is to remove air and moisture from the A/C
system. That is typically achieved when the low pressure compound gauge shows
a level of vacuum of about 29.9” has been attained. However, understand
that the compound gauge is not a very clear indication of how well your vacuum
pump is working.
The
most accurate check for vacuum pumps is to use a micron vacuum gauge. That
will measure the level of vacuum in microns. One micron is equal to one millionth
of a millimeter. The lower the number of microns the deeper the vacuum.
Now
when looking at your compound gauge, can you tell the difference between
28.9 inHg and 29.9 inHg of vacuum? Probably not. The scale is far too small
to see the real difference. But understand that at 28.9 inHg, you are only
pulling about 50,000 microns. At 29.9 inHg you are pulling about 100 micron.
What’s
the difference? Well, water only starts to boil when the vacuum reaches a
level under 1,500 microns. Deep vacuum is considered to be a level of vacuum
under 500 microns. If you can not be sure how good a vacuum your pump is
pulling, you should take the time to invest in a micron vacuum gauge and
find out exactly what level of vacuum it is pulling. Additionally, there
is other information available that provides even more details about vacuum
pumps and What Vacuum
Pump Manufacturer’s Don’t Want You To Know.
In
the meantime, your best defence is to maintain a clean vacuum pump and complete
proper oil changes at least every 15 - 20 hours of operation, and more frequently
when working on severely contaminated A/C systems. |
This
was probably one of the best books on recharging air conditioning that I
have seen...
