Need Help - AC problem with a 2000 Honda CRV AC
Gene
We just did a successful vacuum and leak test,
then recharged the system with 134a.
At a constant 3000 RPMs, and with a set of AC gages attached
to the low & high ports, the AC system does this:
1. The low pressure gauge rises in pressure until the high
limit (low side) switch disengages the AC clutch. The high pressure gauge
is within limits at this time.
2. When the low pressure gage returns to safe pressure, the AC
clutch engages. This time the high side pressure gage begins to climb
until it reaches the high side limit in PSI, and the AC clutch disengages.
The high side pressure declines to a safe PSI and the AC clutch
again engages. Now go back to #1 above and start the low pressure side
rising to the upper limit. It is a continuous loop.
The above is an endless loop of reaching max low PSI, shut off, reaching
max high PSI, shut off, reaching max low PSI, shut off ...
Even at a steady 3000 RPM, the above constant cycling does not do a
satisfactory job of cooling the car.
What's the problem?
THANKS,
Gene
Comboverfish
Please give the following in actual numbers:
1) your interpretation of low side unsafe pressure
2) high side cut-off limit
3) high side safe turn-on point
Also, what exactly is a "high limit (low side)" switch?
I'm thinking you don't know how this system operates. I'll be glad to
help if you fill in the above data.
Toyota MDT in MO
Gene
"Comboverfish" <combov...@yahoo.com> wrote in message
news:1185995371.9...@x35g2000prf.googlegroups.com...
>
> 2) high side cut-off limit
It was near 400PSI when it shuts off
>
> 3) high side safe turn-on point
Can't remember,but it was > 150PSI
>
> Also, what exactly is a "high limit (low side)" switch?
When the low side gets near the 110PSI area, it shuts off.
>
> I'm thinking you don't know how this system operates. I'll be glad to
> help if you fill in the above data.
LOL - I definitelly do not understand this one.
I would expect it to run at ~ 30-50 PSI on the low side and
about 150 to 200 PSI on the high side, but not sure ?
Thanks,
Gene
>
> Toyota MDT in MO
>
Comboverfish
> "Comboverfish" <comboverf...@yahoo.com> wrote in message
I said that not to be rude, but because you suspected high low side
pressures as a cause for the system to shut down. This system (from
the factory, atleast) has only one pressure switch that can control
the compressor's engagement. It is a dual pressure type switch
located on the high pressure line (the smaller diameter line) near the
front of the vehicle, located in or near the receiver drier but I
don't remember for sure. This switch will shut down the compressor at
about 450 psi and also if the pressure drops below about 30 psi.
There will be a "hysteresis range" of pressure around those points
with this type of switch; this will cause it to stay off for a while
after it passes back into the acceptable range of operation. Perhaps
this hysteretic action is what you were describing.
The bad news is that your symptoms do not lead to one conclusion. It
doesn't sound like the dual pressure switch is causing the cutoff
every time, and the gauges' behaviors don't lead me to a solid
conclusion. I think I would have to see it for myself, or assume
there is a moving piece of blockage in the high side, either in the
condenser or the drier. Perhaps you have too much oil in the system
too.
If both gauges went high at the same time, climbing gradually, I would
say it is probably overcharged. How much R134a by weight did you
install? Did you reference the refrigerant charge sticker underhood?
To what indicated vacuum and for how long did you evacuate?
If the high side all-of-a-sudden pegged hard and the low side rose
quickly afterwards I would suspect high side blockage. Condensers are
the most common area for this manner of restriction.
Another though is an inaccurate gauge set or the valves were open or
leaking internally (along with an A/C problem).
Toyota MDT in MO
Gene
I agree with your best guess, that it could be some blockage on the high
side.
The car was recently purchased used by my kids, so we have no historical AC
data.
I did three similar AC compressor replacements with these same gauges in the
last month and all went 100% successfully - so I am pretty sure the gauges
are OK.
I pulled ~ 25-26 vacuum for ~ an hour with both low & high sides open.
That should have been enough to get the moisture.
Because I am doing it myself, here is the approach that I like, and will
probably
do in this case, assuming the problem persists.
1. Go to a local salvage yard & find the best AC compressor from a "wrecked"
car.
It must come from a reputable yard & have an unconditional 100% return for
90 days.
To test it, I pour in an ounce of the appropriate oil into the compressor,
turn it over by
hand to check compression a few times, then pour out the oil onto a clean
napkin.
It must have good compression & no foreign matter in the oil. Next I test
the clutch with
a 12VDC+ to the clutch pin. Finally, I spin the pulley and use a stethoscope
to listen
to the bearing free wheel. If all of the above are OK, I install said AC
compressor.
Here is my logic for the above:
a. Factory AC compressor are WAY too expensive.
b. The lower priced new compressors are made in China.
c. The rebuilt compressors are the patched trash that were returned.
d. The used ones per above are the only ones that are in good condition &
low priced. So far, I have never had a bad one. Just check them out first.
2. Buy all new O rings, seals, dryer, filter, etc. - I even replace the
low/high port valves.
3. Remove the old compressor, etc. & flush the system
4. Install the used compressor with oil, etc. , do a complete vacuum & leak
test - then
fill with 134a.
The TOTAL out-of-pocket cost runs from $100 to $250, depending on the car.
In that it is so inexpensive to just do it right, this is probably what is
best for this Honda.
It's really not worth the time and effort to trace down a potential clogged
point in the system
for $200 or so.
However, I really would like to know what the problem is with this Honda,
I'm just currious:-)
THANKS,
Gene
"Comboverfish" <combov...@yahoo.com> wrote in message
news:1186061575.6...@r34g2000hsd.googlegroups.com...
Comboverfish
> Thanks.
>
> I agree with your best guess, that it could be some blockage on the high
> side.
>
> The car was recently purchased used by my kids, so we have no historical AC
> data.
>
> I did three similar AC compressor replacements with these same gauges in the
> last month and all went 100% successfully - so I am pretty sure the gauges
> are OK.
Sounds logical, if other properly operating systems gave you
acceptable low and high side pressures on your gauge set.
> I pulled ~ 25-26 vacuum for ~ an hour with both low & high sides open.
> That should have been enough to get the moisture.
You should be seeing about 28"-30" on a low side gauge when under full
vacuum. In actuality, about 29" is all you can pull depending on
elevation, but an indicated 25"-26" worries me that maybe the vac pump
isn't working properly.
Sounds like a good method to obtain a good, working compressor,
but.... what makes you think that a compressor and drier replacement
is going to fix this CR-V? What's wrong with the current compressor
that you can prove with testing?
> The TOTAL out-of-pocket cost runs from $100 to $250, depending on the car.
>
> In that it is so inexpensive to just do it right, this is probably what is
> best for this Honda.
> It's really not worth the time and effort to trace down a potential clogged
> point in the system
> for $200 or so.
If you can get the system to run long enough, you can test
temperatures along the high pressure lines, drier, and condenser
tubing to locate an unusually cold spot. That would be where the
restriction is (unless you are dealing with a massive overcharge... I
still haven't seen an answer to my charge quantity/method question).
Toyota MDT in MO
Gene
Good idea ~ testing for a cold spot.
The AC is working, just cycling on and off - cooling is
marginal at best. Can't hurt anything to just run it for a while.
I placed 2 full cans in it - which was enough to make it cool.
I was afraid to stuff any more into it, given the 400PSI readings.
The easiest way to resolve the problem is to just replace
everything per my earlier post. I think I can do it for
~ $200 total. Other than my just being curious, it's not
worth spending the time to find a clogged area. A blocked
area is caused by something broken in the system - usually
the compressor. So just replacing everything for $200 is the
only real solution as I see it. I was hoping that there was a common
problem with this specific condenser in this model Honda.
Thanks,
Gene
"Comboverfish" <combov...@yahoo.com> wrote in message
news:1186074095.7...@g12g2000prg.googlegroups.com...
Comboverfish
> The AC is working, just cycling on and off - cooling is
> marginal at best. Can't hurt anything to just run it for a while.
450 psi spikes can't hurt? Mmmmkay...
> I placed 2 full cans in it - which was enough to make it cool.
> I was afraid to stuff any more into it, given the 400PSI readings.
24 oz is approximately the correct charge but I don't have the spec
handy. If the cans of R134a had other crap in them you may have just
boned the system. Either way, 24 oz of pure refrigerant wouldn't
cause this odd pressure behavior.
> The easiest way to resolve the problem is to just replace
> everything per my earlier post. I think I can do it for
> ~ $200 total. Other than my just being curious, it's not
> worth spending the time to find a clogged area. A blocked
> area is caused by something broken in the system - usually
> the compressor.
Usually not.
> I was hoping that there was a common
> problem with this specific condenser in this model Honda.
It's a reality with most modern high efficiency condensers. I don't
know if that particular part is more failure prone than others.
Toyota MDT in MO