Hey how is it going do it yourselfers, today
I am going to show you how you can use an A/C manifold gauge set to diagnose problems
with your cars AC system, but not just that I will also go over how you can use it to
add refrigerant to your ac system as well. Alright so on the left side we got this in
blue this is going to be for the low pressure side, and this gauge on the right side is
going to be for our high pressure side. And than we got these two connectors at the
end that will attach to the pressure ports on our high and low pressure lines of our
ac system and thats how we'll get the pressure readings on these gauges. And these guys are just attached to the manifolds
at the ends here, and these don't do anything they are just there so that you can attach
these to them, they have no practical purpose besides that. And the way these guys work is that there
is a quick connect coupler at the end of them which you pull out and than you would put
this over the pressure port so this one is going to be the low side pressure port and
than once you let it go it holds it in place and than you run down this valve, this valve
here would press down on a schrader valve that's on your connector for the low side
and open up the system to your ac manifold gauges.
Alright next let me explain to you what these
two knobs here do or actually in this case this one knob, there is another knob thats
supposed to be here just in red but it's broken on mine and its missing but just imagine there
is another knob like this here that's red. Once you open these, these will open up your
low and high pressure sides to center line, this yellow line. And this center line is used to add either
refrigerant to your system, or completely evacuate the system of refrigerant or pull
a vacuum on a system after a repair to confirm that there are no leaks in the system.
Now as far as where you attach your connectors
it's pretty, if you are lucky enough you'll have a plastic cap like this that says H on
it. And once you unscrew that you'll see the pressure
port where you would connect your high pressure side, but if you are not lucky enough to have
those plastic caps fear non the connector that goes to the high pressure side is going
to be the diameter on the inside of it is going to be larger than the one that goes
on the low pressure side.
In so many words these are basically dummy
proof and you really can't put them on wrong. Alright so I going to go ahead and attach
this to our high pressure side, after I attach it you just want to pull on it slightly make
sure it's secured in place. And also before you put this on you want to
make sure your valve is turned counter clockwise all the way so that the pin is not going to
press on the schrader valve immediately, but than after you attach it than you want to
turn this clockwise so that the pin that's inside here press on the schrader valve and
there I don't know if you guys heard it that just opened the system to our ac manifold
gauge set.
Alright so we come back up to our pressure
gauges and as you can see on the high side now we have about 75 psi of pressure on this
side and this is going to be considered your static pressure which means this is the pressure
you have with the car sitting turned off and the compressor not engaged. Alright next I am going to connect the low
side which is back here. Alright as you can see we've got about 60
psi of pressure on the low side as well which is pretty close to what on the high pressure
side and this is what you want to see. So on this board I've drawn up two types of
common ac systems that are out there, one type is the one that has an expansion valve
and the other type is the one that comes with an orifice tube instead and what we have on
this car is this system here so we got our ac compressor which is this guy here which
compresses the refrigerant and starts the high pressure side of your ac system which
goes from your ac compressor to your condenser and from there to your receiver drier and
than your expansion valve and than after that is the low side of your system which is the
evaporator, which is the one that's inside your dash inside your car with your blower
motor inside there blowing over it and than the return line that goes to your ac compressor
so this is the low pressure side on this system and everything in red is your high pressure
side.
Alright so if you attach your pressure gauges
to a car that's been sitting for a while the pressure on both sides should be fairly close
to equal because once the compressor is turned off the pressure equalizes on both sides,
the pressure leaks from the high pressure sides to the low pressure side and without
the ac compressor running one side is not going to have more pressure than the other
but if you attach your pressure gauges and this side is alot higher than the low side
than that means you have a clog here that's not letting the refrigerant to slowly get
back into the low pressure side equalizing the system and that usually the culprit for
that is a clogged orifice tube if you have this system or an expansion valve that's stuck
closed.
Now unless you have a completely clogged orifice
tube or an expansion valve that's stuck completely closed, it's not very common to have those
numbers with the ac turned off and the car not running. Get in your car and turn on the engine, turn
on your fan all the way to high make sure you're in maximum cool and turn on your AC. Next you want to wait a few minutes and with
your AC compressor clutch engaged you want to take your measurements and as you can see
on the low side we got about 15 17 on the low side and about 120 on the high side.
So next once you get these numbers you want
to look into your repairs manual and compare those numbers to the numbers you are supposed
to have given the temperature and the humidity at the time you took the measurements. But here are some very general numbers that
could guide you to try to diagnose problems with your car. Alright so here today our temperature is about
68 degrees fahrenheit and our relative humidity is above 40% and the pressure we are looking
to get at the low side should about twenty five to thirty seven and the high side should
be about eighty three to one fifty five. Alright so according to the numbers we got
earlier we are definitely on the low side for the low pressure side and also on the
high pressure side we are towards the low side as well which basically means we are
simply low on refrigerant.
And that about sounds right because on this
car when you turn on the ac you don't get cold air you just get slightly cool air coming
out of your air vents. Alright next lets talk about different numbers
that you could get on your gauges, so if your numbers on the low side and on the high side
are higher than what you are supposed to have than that would indicate that you either have
too much refrigerant in the system or you could have air that has gotten in your system
as well. Also if your ac condenser is unable to cool
the refrigerant that's passing through it, either because your ac fans are not coming
on or junk and dirt and debry that could be logged in front of it and not allowing air
to pass over it, than again you could potentially be high on both sides as well.
Alright next lets say if you get about the
same numbers on both sides, and if you are getting the same numbers on both sides with
the air compressor running in other words your ac compressor clutch engaged and you
are still getting the same numbers than that's going to mean basically your compressor is
not doing it's job which basically to compress the refrigerant , to take refrigerant from
one side suck in refrigerant from the low side and compress it into the high pressure
side creating low pressure on the low side and high pressure on the high side and if
it's not doing that than that probably means it's shot and needs to be replaced.
Alright so in the next scenario we are going
to say that the numbers for your low side are lower than what they are supposed to be
and the high side are higher than what they are supposed to be. Alright so if that's the case you more than
likely have a clog in your high pressure side which is basically blocking the refrigerant
from passing to the low pressure side raising the pressure on the high side and lowering
the pressure on the low side, the main culprit is going to be if you have a system with an
expansion valve the valve that's stuck near the closed position or a clogged receiver
drier, now if you have a system that has an orifice tube instead of an expansion valve
than the main culprit is going to be the orifice tube, see on this system you don't have a
receiver drier on the high pressure side but instead you have an ac accumulator on the
low pressure side.
Alright so next lets talk about the trickiest
set of numbers you can get while diagnosing an ac system which is too high of a psi on
the low side and too low on the high side, if this is the case if you have an expansion
valve set up than that could potentially be your expansion valve thats stuck open or near
the open position allowing too much refrigerant to pass through, or a problem with the check
valves inside your ac compressor, see these check valves like on the low side they only
allow refrigerant to get in and not get back out and on the compressor side or the high
pressure side they only refrigerant to get out and not get back in. But if like this check valve is not opening
enough or it's kind of closed than you are going to build up too much psi on this side
but more likely culprit is going to be your expansion valve stuck near the open position.
Now if you get these numbers on a set with
an orifice tube than, see it wont be your orifice tube because an orifice tube just
has a set opening or a set orifice you could say which only which is not adjustable so
it can't be stuck open like an expansion valve so the culprit is going to be either your
ac compressor or your ac accumulator if its clogged would raise the pressure on the low
side and therefore lower the pressure on the high side.
Alright enough of that so now let me show
you how you can use this to add refrigerant to your car's ac system. So obviously you'll need a can of refrigerant
you'll also need a can tap like this and the way this works is that you'll screw this on
the can and than once you screw in this valve there's a needle at the end of it that'll
come out and puncture the can opening up the refrigerant to the valve and this is going
to be connected to this yellow line here and than from here we are going to open up the
valve to the low side and than that's going to suck in the refrigerant through this line
and the can to the low pressure side.
And once again when you are screwing this
on the can make sure this valve is turned counter clockwise and it's in the open position
and next we will screw on our yellow line and than we start turning this in. Alright so once again we are going to get
in the car turn on the engine and turn on the ac and come back here and open up that
valve that will open up the system and suck in the refrigerant from the can through this
yellow line and the blue line into the engine. Alright so turn this counter clockwise and
you can turn this upside down to help with the flow, and here is a closer shot and you
can actually see the refrigerant and all the oil that's in that can pass through here to
your low pressure side. Alright with our can pretty much empty we
are at just about 25 on the low side and just above 150 on the high pressure side which
is about right, and now we got really nice cold air coming out of these air vents, awesome.
And that should about cover it guys hope you
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next time..
