air conditioning Q - topping off R134a at home?

[Randy G.]

So the air conditioning of my '93 960, R134a system is working but not
all that well. Cool, but not cold air. I thought that one of the home
recharge kits would be OK to top off the system. I have been reading
and found a lot of generic tips, but not specifically for this car,
and do I need to add, "Chilton was of no help"?

I got a home recharging kit with a low-side pressure gauge, but have
read that the total coolant in the system should be evacuated,
weighed, then replaced with the addition of R134a to create the
correct total amount. I was thinking that I would run the air
conditioning at idle, on high, and put a fast-reacting digital
thermometer's sensor in a vent, and while staying in the correct
charge zone on the gauge, SLOWLY add R134a while watching the
temperature of the air coming out of the vent.

First, is the port next to the 'cylinder' (looking like an aluminum
propane bottle- is that the accumulator? a guess as the Chilton didn't
even have a diagram with the parts named) near the dash the correct
low-side port? A cursory inspection revealed this to be the only one I
have found so far, but it was late and dark when I looked.

The black plastic, screw-on cap on that port says something like "Max
6Nm" on it. I thought Newtom meters was a torque setting and so i am
assuming that this is in reference to the torque to be applied to the
charging adaptor affixed to teh prot when charging and nothing to do
with the level of charge itself. Is that right?

Am I heading in the right direction? Is it worth a try? Should I just
return the kit and take the car to a shop for recharging? Should I
just move to a colder climate? Hey, Rob? What does a home go for where
you live? ;-)

from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

 

[Randy G.]

So the air conditioning of my '93 960,...snip

Can anyone read my original post in this thread? Having probs in othe
groups and wondering if anyone say it? THANKS and sorry for replying
to my own post.
from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

 

[Rick Frazier]

Randy:

We can't tell if you should move somewhere else unless we have some idea
of where you live now...

OK, if you're just getting cool air, when you had cold before, what
temperature are you actually getting, and what's the ambient temperature?
Generally, with a normally working system, you should see a good 30 degree
drop from outside air to inside discharge while at high idle, after
running for a few minutes.

Freon tends to be a funny thing, especially 134a. Too much can actually
cause less cooling than not quite enough. Generally, the kits you can get
at the local department or parts store will only let you read the low side
pressure, and that's just not enough to know what is really going on.

Yes, as you've read, the "right" way is to have the system evacuated and
recharged with the correct amount of refrigerant. However, many people
have found that if they have low pressure on the low side, along with
insufficient cooling, if they add a partial can, everything works fine.
Adding a full can, however can really be "too much of a good thing" if it
exceeds the capacity of the system because it puts a very high load on the
compressor and can cause permanent damage (and I can tell you, compressors
are not inexpensive!).

The low pressure port is a different size from the high pressure port on
R134a systems, so you shouldn't be able to connect to the wrong one, but
if you can't identify it from the information you have, perhaps you should
get someone to give you a hand.

Thanks
--Rick

 

[Randy G.]

Randy:

We can't tell if you should move somewhere else unless we have some idea
of where you live now...

It's freakin' hot here! Nor Calif. been around 90-95f for the last
week or so. Down in the valley it's even hotter!

OK, if you're just getting cool air, when you had cold before, what
temperature are you actually getting, and what's the ambient temperature?
Generally, with a normally working system, you should see a good 30 degree
drop from outside air to inside discharge while at high idle, after
running for a few minutes.

I had thought about all that, but had not quantified it at all. I
would say that it is not 30 cooler, but I will check that out before I
consider adding any 134a. I did get the gauge that measures the low
side, and I have identified it correctly as the high side port SEEMS
to be on the back of the compressor, by feel, but my head is to big to
get down in there to see ;-)

Freon tends to be a funny thing, especially 134a. Too much can actually
cause less cooling than not quite enough. Generally, the kits you can get
at the local department or parts store will only let you read the low side
pressure, and that's just not enough to know what is really going on.

Yes, I have been reading about that all over the net. This is what
made me think that the combination of the gauge and a digital
thermometer with a long probe wire will let me check the gauge as well
as the temperature of the air coming out through the vent at the same
time. I can add little bits of 134a and see the effect on the
temperature of the air coming out.

Yes, as you've read, the "right" way is to have the system evacuated and
recharged with the correct amount of refrigerant. However, many people
have found that if they have low pressure on the low side, along with
insufficient cooling, if they add a partial can, everything works fine.

That's what I thought. I wouldn't even think of adding 134 if i didn't
have the gauge, but thought that I would ask here first anyway. What
with spending over $200 on a rack and pinion last week I thought I
would try to save a few dollars right now on this job... I figured
that if the gauge and fill kit with a large can of 134a cost $25, it
would still be less then going to an AC shop to find out that the
level was low or not...

Adding a full can, however can really be "too much of a good thing" if it
exceeds the capacity of the system because it puts a very high load on the
compressor and can cause permanent damage (and I can tell you, compressors
are not inexpensive!).

There are Inexpensive parts on a VOLVO!? You got a list? ;-)

The low pressure port is a different size from the high pressure port on
R134a systems, so you shouldn't be able to connect to the wrong one, but
if you can't identify it from the information you have, perhaps you should
get someone to give you a hand.

Then I did find the correct port. makes sense that it is up where it
is easy to get to like most other service items on this car.. The
tranny dipstick is another matter all together!

And thanks for the reply. Much appreciated!

from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

 

[David Taylor]

There are Inexpensive parts on a VOLVO!? You got a list? ;-)

I can start that off:-

The little U shaped plastic screw covers on the roof rails.

 

[Jeff Lesperance]

The kit should have instructions on it. I would follow the gauge that
should be included, but be careful not to overcharge. The 6 newton-meter is
the torque, not a lot really - basically hand tight. The temp may not
provide info for over charging. Does the ac cycle on off? If so, add a bit
and see if it stops. I use the intermatic kit and have good results on my
850.

Jeff

 

[Randy G.]

The kit should have instructions on it. I would follow the gauge that
should be included, but be careful not to overcharge. The 6 newton-meter is
the torque, not a lot really - basically hand tight. The temp may not
provide info for over charging. Does the ac cycle on off? If so, add a bit
and see if it stops. I use the intermatic kit and have good results on my
850.

I played with it last night. I added some and then stopped as I have
decided there are other issues.. maybe.

the high pressure pipe got quite cold under the hood where it enters
the cars and was dripping from condensation. The air in the car was
cold at first then seemed to get warmer. Icing? I am not sure. I also
believe that I have a bad vac actuator motor in there as well becasue
the cold air only comes out of the two dash vents nearest the doors,
and the two center vents in the dash blow warm air. Maybe the heater
control valve is also bad? I know the dual acting vac motor at the
driver's foot area is bad and needs to be replaced. I was considering
doing the cut and hack job to replace it (opening a hole in the air
box behind the console to access the flapper), but it seems I also
have other issues to deal with. I think I might get the Volvo shop
book on the heating air conditioning system and see what that says. I
don't mind taking the time to remove the dash and do the job
correctly, but would like to know ahead of time what it entails, what
is wrong, and to have the repair parts on hand to minimize down time.

The compressor cycles a lot (at least that's the way it seems to me)-
like ABOUT every five or seven seconds on then abot the same amount of
time off. The gauge hooked up to the low pressure side of the system
indicates that the compressor engages when the pressure hits the low
end of the "good" zone, then the compressor runs, and then the clutch
disengages when the pressure hits the high end of the "good" zone. The
gauge is calibrated to show that this range is 25psi to 45psi. I can
assume a lot of things from that, but what does it really mean?
Anyone?

I am addind this info to assist others as well as to learn what it
happening... from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

 

[Rod Gray]

If you have a low side guage the pressure when the charge is correct should
be 30-32 lbs. If it isn't cold then it is not enough but you see 30 lbs.
because the orifice tube is clogged. Sometimes evacuating the system from
the low pressure side will clear it but it is better to disconnect the hose
on the dryer and clean and reinstall it. Use a new o-ring. That is a sign
the compressor is on it's way out, but you may get years more service out of
it.An oil charge with sealant is a good idea while you are at it.

 

[Randy G.]

If you have a low side guage the pressure when the charge is correct should
be 30-32 lbs. If it isn't cold then it is not enough but you see 30 lbs.
because the orifice tube is clogged. Sometimes evacuating the system from
the low pressure side will clear it but it is better to disconnect the hose
on the dryer and clean and reinstall it. Use a new o-ring. That is a sign
the compressor is on it's way out, but you may get years more service out of
it.An oil charge with sealant is a good idea while you are at i

Rod,
see my response to Jeff's post in this thread and let me know what
you think...

from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

 

[Mike F]

I played with it last night. I added some and then stopped as I have
decided there are other issues.. maybe.

the high pressure pipe got quite cold under the hood where it enters
the cars and was dripping from condensation. The air in the car was
cold at first then seemed to get warmer. Icing? I am not sure. I also
believe that I have a bad vac actuator motor in there as well becasue
the cold air only comes out of the two dash vents nearest the doors,
and the two center vents in the dash blow warm air. Maybe the heater
control valve is also bad? I know the dual acting vac motor at the
driver's foot area is bad and needs to be replaced. I was considering
doing the cut and hack job to replace it (opening a hole in the air
box behind the console to access the flapper), but it seems I also
have other issues to deal with. I think I might get the Volvo shop
book on the heating air conditioning system and see what that says. I
don't mind taking the time to remove the dash and do the job
correctly, but would like to know ahead of time what it entails, what
is wrong, and to have the repair parts on hand to minimize down time.

The compressor cycles a lot (at least that's the way it seems to me)-
like ABOUT every five or seven seconds on then abot the same amount of
time off. The gauge hooked up to the low pressure side of the system
indicates that the compressor engages when the pressure hits the low
end of the "good" zone, then the compressor runs, and then the clutch
disengages when the pressure hits the high end of the "good" zone. The
gauge is calibrated to show that this range is 25psi to 45psi. I can
assume a lot of things from that, but what does it really mean?
Anyone?

I am addind this info to assist others as well as to learn what it
happening... from Randy & Valerie
__ __
\ \ / /
\ \/ /
\__/olvo
1993 960 Estate

What you can determine from your cycling pressures is that the cycling
switch is working correctly. What you can determine from the frequency
of cycling is that the system is low on charge. It's hard to know just
how much is needed to bring the charge up to full without a proper
evacuate and recharge, but as you add some the cycling frequency should
go down. When the A/C is working hard (i.e. hot day) then there should
be no cycling. Add about another half pound and see if the cycling
frequency goes down. If not, then you have other problems.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

[Randy G.]

What you can determine from your cycling pressures is that the cycling
switch is working correctly. What you can determine from the frequency
of cycling is that the system is low on charge. It's hard to know just
how much is needed to bring the charge up to full without a proper
evacuate and recharge, but as you add some the cycling frequency should
go down. When the A/C is working hard (i.e. hot day) then there should
be no cycling. Add about another half pound and see if the cycling
frequency goes down. If not, then you have other problems.

Thanks for that reply, Mike.

I did take the car for a short ride yesterday and the air conditioning
is working much better after adding a few ounces (? a guess) of 134a.
The air from the center vents was actually cold (was warm before) and
the air from the side vents was actually much colder. The addition of
a small amount of 134a made a big difference for me.

I have come to the conclusion that using the low-side gauge on the
Volvo is not a very accurate method at all for this job. Too many
variables. The cycling frequency did get lower after adding some 134a
but without knowing all the other factors and how they interact (air
temp, humidity, etc.), there is now way to use that to accurately
judge how much is enough or too much.

I should also have weighed the can of 134a before adding so I could
tell how huch I used. The can says 14ozs.(net weight) and I probably
only added about two or three ounces (about 75 grams).

Knowing that it should not cycle at all (or at least barely so) when
the weather is really hot is good to know as well.

Thanks again! Much appresicated!
__ __
Randy & \ \/ /alerie's
\__/olvo
'93 960 Estate

 

[Mike F]

Thanks for that reply, Mike.

I did take the car for a short ride yesterday and the air conditioning
is working much better after adding a few ounces (? a guess) of 134a.
The air from the center vents was actually cold (was warm before) and
the air from the side vents was actually much colder. The addition of
a small amount of 134a made a big difference for me.

I have come to the conclusion that using the low-side gauge on the
Volvo is not a very accurate method at all for this job. Too many
variables. The cycling frequency did get lower after adding some 134a
but without knowing all the other factors and how they interact (air
temp, humidity, etc.), there is now way to use that to accurately
judge how much is enough or too much.

I should also have weighed the can of 134a before adding so I could
tell how huch I used. The can says 14ozs.(net weight) and I probably
only added about two or three ounces (about 75 grams).

Knowing that it should not cycle at all (or at least barely so) when
the weather is really hot is good to know as well.

Thanks again! Much appresicated!
__ __
Randy & \ \/ /alerie's
\__/olvo
'93 960 Estate

It's not just Volvo where using a low side pressure gauge is not an
accurate method of filling. Because A/C systems all work on the same
principles of physics, and pretty much copy each other in general
design, all systems behave this way. Generally the accumulator will
hold around a half a pound of refrigerant in reserve, so losing the
first bit and adding the last bit doesn't affect performance.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)