Question on 92 740 A/C......

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geronimo

I tried a charge with Dura-Cool. I am not getting much cooling at all
from the A/C. None before (there was a leak on the condenser), and
little after. There is enough that at night when the outside temp is
in the 80s you are cool, but it is overwhelmed by humid mid-90s
weather in the daytime. I didn't replace the accumulator before
recharging. ALso I was told that the orifice tube might be clogged up.
So I have an accumulator ordered (along with the AMM) and also a new
orifice tube. Will pump it down again and refill with R-134 this time.


ANother problem with the A/C is that the blower puts out a puny volume
of air. I know it is rotating freely. I know it is controlled somehow
by computer, because every time you go up even a slight uphill grade
(or accelerate), the blower cuts back and there is practically no air
blowing out the vents. Also the compressor is cut off under load. I
would really like to try disabling this feature and see if car still
performs OK, because it makes it get even hotter. I ckecked the
voltage to it when it is going "full blast" and it is getting about
the full system voltage.....maybe it just doesn't blow nearly the
volume of air that a modern sedan does. But I don't know, since I
don't have another 740 to compare with. Could I get some other more
powerful motor for more air volume?
How can I check to see of there is some restriction of the air inlet
to the blower? I think there is a vacuum operated door, but maybe it
is a hot/cold blend door on the outlet side of the blower.
ALso, I need to know where the orifice tube is installed....I
don't have a clue where to find it.
Its probably not the fault of the Dura-Cool, but there is some
other issue with it.

Thanks, Geronimo
 
geronimo said:
I tried a charge with Dura-Cool. I am not getting much cooling at all
from the A/C. None before (there was a leak on the condenser), and
little after. There is enough that at night when the outside temp is
in the 80s you are cool, but it is overwhelmed by humid mid-90s
weather in the daytime. I didn't replace the accumulator before
recharging. ALso I was told that the orifice tube might be clogged up.
So I have an accumulator ordered (along with the AMM) and also a new
orifice tube. Will pump it down again and refill with R-134 this time.
Click to expand...

It's probably a clogged orifice, while you've got the system open,
disconnect all the joints one at a time and replace all the O-rings, if
you're gonna do it, you may as well do it right. Charge with the correct
weight of refrigerant and it should work well, mine blows icy cold air when
it's 90 outside on the highway.
 
I got all parts to recharge again, including the new accumulator and
orifice tube. Only problem now is that I don't have a clue where the
orifice tube is on my 92 740 turbowagon. Where do I look for it?
 
geronimo said:
I got all parts to recharge again, including the new accumulator and
orifice tube. Only problem now is that I don't have a clue where the
orifice tube is on my 92 740 turbowagon. Where do I look for it?
Click to expand...



It's in the liquid line right at the firewall, pull the fitting off and
you'll see it stuck in there, just pull it out with some long nosed pliars.
 
Another ac question.....Just in case I have too much oil now in the
system, I think I should drain it at the lowest point as much as
possible before evacuating the system. I suppose being over-serviced
with oil would reduce the amount of refrigerant that it will take, and
so could cause poor cooling as well. So if I put 33 oz (nearly 3 cans)
of R134 into the system, how much oil should I put in? I have
purchased only two cans of refrigerant, which I think is nothing but
refrigerant.... so if I buy another 12 oz can with oil, will it be
enough?
I have done a couple of recharges, the first with oil, and I never
really drained the original oil out...so that is why I am thinking I
had better really empty the system completely this time, to ensure the
full factory charge of refrigerant will go in.
I am also guessing that I will need to open a low side line at
lowest point as well as a high side line at lowest point...right?
Thanks, Geronimo
 
geronimo said:
Another ac question.....Just in case I have too much oil now in the
system, I think I should drain it at the lowest point as much as
possible before evacuating the system. I suppose being over-serviced
with oil would reduce the amount of refrigerant that it will take, and
so could cause poor cooling as well. So if I put 33 oz (nearly 3 cans)
of R134 into the system, how much oil should I put in? I have
purchased only two cans of refrigerant, which I think is nothing but
refrigerant.... so if I buy another 12 oz can with oil, will it be
enough?
I have done a couple of recharges, the first with oil, and I never
really drained the original oil out...so that is why I am thinking I
had better really empty the system completely this time, to ensure the
full factory charge of refrigerant will go in.
I am also guessing that I will need to open a low side line at
lowest point as well as a high side line at lowest point...right?
Thanks, Geronimo
Click to expand...


If you never drained the mineral oil out before converting, you likely have
a real mess in there now. R134 reacts badly with mineral oil and breaks it
down. You should definitely remove the compressor, drain all the oil, then
flush out the lines, evaporator, and condenser with refrigeration solvent.

IIRC the oil charge is something like 8oz, I found the Volvo retrofit
instructions online somewhere when I did mine years back.
 
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