air conditioning problem

I have a 1992 honda civic that used the old school R12 refrigerant. My
brother a few years back did a motor swap on the car and of course swapped
out the compressor for the a/c at the same time. The new compressor is off
a brand new car so its r134a compliant. To get the a/c working again he
took the vehicle to a shop that supposedly changed out the seals and
evacuated and rechraged the system with r134a refrigerant.

All was working well up until this spring when my a/c stopped working.

I recharged the system with a set of brand new gauges and genuine virgin
r134a refrigerant. All was working well up until my curiousity uncovered
something quite interesting.

My a/c blows about 10-12 degrees celsius which is acceptable for ambient
temp of about 20 degrees celsius. I decided to hook up a set of gauges to
my car and found the readings to be quite off from what I think they should
roughly be.

The low side suction pressure is about 23-28 psi and the high side is at a
crazy 250-260 psi! The line to the condensor is extremely hot which i
already know is not normal. The car cools reasonably well so I'm lost as to
what could be wrong. According to my honda service manual a excessive high
discharge line pressures and abnormally hot condenser lines indicates a
restricted refrigerant flow in the system.

here are some observed items:

1. the receiver drier is the original R12 receiver drier (the shop was
stupid enough not to change it out to comply with r134a)
2. There is a small refrigerant leak from the acme fitting on the low side.
3. The discharge line into the condenser is insanely hot
4. The suction line is noticably cold
5. the receiver drier feels very warm to the touch and the line going to
the evaporator is also very warm to the touch.
6. The ambient temperature isn't hot enough to make the suction line to
sweat.
7. The high side pressure before starting the car is only at 90 psi. As
compressor run time increases the higher the pressure and the higher the
condenser line temps.
8. When the compressor cycles on and off the high side pressure can
fluctuate as much as 25-30 psi. When the compressor pumps the pressure
shoots up very fast and when it stops it drops fairly rapidly down about
20-30 psi before really coming to a stop. After the cycle starts over again
with discharge pressures getting higher and higher.
9. I highly doub the system is overcharged b/c the low side pressures are
so low.
10. The compressor i am using is brand new straight from honda.


With ambient temps on the cooler than average side and a discharge pressure
so high I can only imagine what the end result would be when the ambient
temp shoots to over 30 degrees. My a/c would literally explode!

I can't see how the system is restricted other than two places. The
expansion valve or the receiver drier.

The expansion valve couldn't be stuck closed b/c I get a decent amount of
cooling
The expansion valve couldn't be stuck open b/c the evaporator doesn't freeze
over
The receiver drier is the original r12 drier so that should be an obvious
sign of bad a/c retrofitting. I will change that out

I was good at fixing R12 a/c systems in older cars but this retrofitted
civic is a tough one to figure out. I don't want to take it to honda and
spend 500 bucks to fix it when I have all the equipment to do it.

Can someone tell me what the heck is wrong?

Thanks

 

You can find the pressure charts for that car with for R134a at
http://www.honda.co.uk/owner/civicmanual/pdf/22-20.pdf.

R134a (1,1,1,2-tetrafluoroethane) is a larger molecule than R12
(dichlorodifluoromethane) so I would imagine that the expansion valve
should be larger to accommodate that. Was it replaced when you had the
seals etc. replaced?

 

I think you're probably on the right track with the receiver/dryer but
while the system is open take a look at the oil which is lurking around at
the fittings and in the receiver. Did the shop which did the conversion
flush out the old R-12 petroleum-based lube? Which synthetic oil did they
replace it with - I'd assume there'd be some lube left in the "new"
compressor, likely PAG - but what did they add to bring the lubricant up to
the correct level?

Take a look at the Forum at www.aircondition.com and search the msgs there
for "black death". PAG oil is particularly hygroscopic and a mixture of
moisture and old petroleum-based lubricant has led to the formation of a
thick black sludge which plugs the A/C lines. If your low side gets to a
low enough pressure and there is even a minor leak which allows moisture to
get sucked into the system, bad things can happen even with PAG only; add
in some old R-12 lubricant and you get the "black death". I hope yours
hasn't gotten that bad yet but putting in fresh PAG without changing out
the old receiver/dryer, which probably had some moisture in it, was a major
blunder IMO.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

I am not sure how to use the charging chart that was sent to me via that
link from George. I am thinking of pulling the entire system and blowing
out the lines and such with compressed air.

How do I know if there is too much oil or moisture in the system.

Strangely the outlet temp from the evap is only about 12C. My toyota which
came from factory with r134a cools down the 7C in the same exact conditions.

So what are the obvious signs of a stuck/closed expansion valve?

Does honda use expansion valve?

What temp are the lines supposed to be at?

How do I know if the receiver drier is starting to plug up?

Thanks

 

That seems commonsensical, but it's frequently not the case. I can think
of several car lines that use the same expansion valve for 12 or 134a.

I think the OP probably has noncondensibles in his system, and I wonder if
his system is properly charged with the correct amount and type of oil.

 

8C drop is cooling "reasonably well?" I disagree.

You have GOT to be kidding.

My guess is the dessicant bag in the drier probably ruptured, and all
the dessicant powder headed downstream and plugged the orifice tube (or
TXV) solid. That would explain the high pressure (the system is mostly
obstructed) and the lack of cooling (a drop of only 8-10C is horrible).

If that's the case, the only solution is opeing up the system, flushing
all the lines, condensor, and evaporator, and replacing the drier and
expansion orifice or TXV (I have no idea if Honda uses a TXV or an
orifice tube, but they perform the same job).

 

I just order a bottle of pag oil and a new factory approved r134a receiver
drier.

will simply re-replacing the compressor oil and drier remove any possible
trace amounts of mineral oil?

I'm sure there is already pag in the system but you never know what idiots
are working on a/c systems with no real experience.

I am hoping that the blockage is in the receiver drier and not the txv. I'm
almost certain the txv isn't clogged b/c it blows cold.

how can I effective flush a condenser myself cheaply?

Can anyone tell me why my head pressure is still so high ?

Thanks a million, your suggestions and comments are greatly appreciated.

Thanks

 

If you're going that far, the recommended method is to flush with solvent
(naphtha ?) first, dry with compressed air and then of course, pull a deep
vacuum for 2hrs or so.

Yes Honda used and continues to use AFAIK, an expansion valve.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

R134a (1,1,1,2-tetrafluoroethane) is a larger molecule than R12
R-134A is actually a SMALLER molecule. That's why barrier hoses are needed.
If you don't believe it, do a Google search using "R134A" and "smaller
molecule".

 

i didn't try the water/pressure drop test. The fan is running on high and
there is very warm air coming out from the condenser. The lines even going
up to the evaporator are warmer than any r134a car that I've touched.

I was thinking of flushing the condenser out and draining all the oil from
the condenser. I also intend to change the receiver drier and dump all the
crap oil in the compressor and replace it with new oil.

I am not sure at this point whether or not I should use ester oil or pag.
The compressor came from factory with pag but my other parts of my a/c used
r12 so techincally ester would be better for it.

What do I do when a compressor calls for pag but my other parts are r12
equipped?

 

swap/clean the other parts, then use pag?

 

Don't flush the hoses unless you see obvious debris. The old oil from the
R12 creates a barrier in the rubber which keeps the smaller 134a molecules
from seeping out. If you flush the hoses, you may wash out this barrier.

 

That's not how it works *at all*. The mineral oil used with R12
*permeates* the hose, thereby keeping the smaller R134a molecules in.
Flushing the hoses does not cause the oil to "unpermeate".

-Stern

 

It's the blends containing R-22 [CH(F2)Cl], such as R-406A, which need
barrier hoses - obviously the substitution of one chlorine atom by a
hydrogen gives a much smaller molecule. I'm not sure about R134a - there
are references which claim it is much smaller than R12 but I have my doubts
and it is apparently not considered small enough for the EPA to insist on
barrier hoses. Obviously R-134a has no chlorine atoms but it does have two
carbons.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

That may be, but it is a fact: R134a is a smaller molecule than R12, which
is why all factory R134a systems have barrier hoses and HNBR or Neoprene
O-rings.

-Stern

 

And some solvents used to flush the systems can also permeate the hoses and
break down the mineral oil. Seen it happen.

 

Do you always have to mangle what others say so you can appear to "correct"
them?

No it's not a "may be" - facts are facts. You'll have to give a reference
other than some auto-repair site for the relative sizes of the molecules
and any necessity of barrier hoses with HCFC-134a. The fact is, as already
stated and snipped, that the EPA has a specific requirement for replacement
barrier hoses when HCFC-22 is used in a system designed for CFC-12; there
is no such EPA requirement for conversion to HFC-134a and HCFC-22 is the
only compound in the repertoire of permissible refrigerants which has the
barrier hose stipulation.

The OP who brought this up was wrong -- HFC-134a is not substantially worse
than R-12 for permeating traditional hose materials -- and the use of
improved barrier hoses with HFC-134a is more due to an initiative by mfrs
to reduce leakage in general, following the all the ozone GW hullabaloo.
IOW R-12 has always leaked too.

As for seals or O-rings, my info has it that the replacement recommendation
there has more to do with the poorer heat tolerance of the traditional NBR
O-ring, which is classed as "good" for compatibility with *all* the various
refrigerants and lubricants, the HNBR having better heat tolerance.
Neoprene is apparently recommended by vendors of blends but is poor on heat
so I doubt that it fits the R-134a application.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

which is more or less a normal pressure

and the high side is at a

That's a little high but 134a runs higher then r12 does so it's pretty
much in the normal range.

The line to the condenser is extremely hot which i

Sounds normal to me, it's supposed to be hot, that why the condenser
is the next step, it cools it down. The line to the condenser is the
high pressure line - it gets hot. Usually way too hot to touch.

The car cools reasonably well so I'm lost as to

From what you have posted, nothing is wrong.


According to my honda service manual a excessive high

That would be true but I don't see that you have either problem based
on your post.

--
Elbridge Gerry, of Massachusetts:

"What, sir, is the use of militia? It is to prevent the
establishment of a standing army, the bane of liberty. . .
Whenever Government means to invade the rights and liberties of
the people, they always attempt to destroy the militia, in order
to raise a standing army upon its ruins." -- Debate, U.S. House
of Representatives, August 17, 1789

 

Sounds more like a condenser problem. Possibly blocked or not enough air
passing across it. Is the cooling fan at the condenser coming on? Try
spraying cold water on it with it running and see if the pressure drops.