Omega Air Con

Unsuprisingly, there are a number of posts about Aircon at this hot
time.
I have a question too.

I believe that my Aircon is struggling (2002 Omega 2.6MV6), and cannot
get
the cabin temp down enough. Although the air is blowing quite cool,
I'd
like to get opinion if it's as cold as would be expected.

I read on a site the other day (different car, to be fair), that with
Ambient of 25C, at 1700rpm, the expected vent temperature should be
around
3.5 degrees. This guy got his system regassed/lubed/dried and was
actually
achieving 2.8C.
With an ambient of 25C degrees outside, what would I expect the air
temperature of the cooled air to be at a fast idle on mine. I asked
Vx
today for a price, which turned out to be more than my local aircon
specialist, and inspired me with little confidence when he reluctantly
told
me i'd get "about 15 mins at vaccuum to dry the system", compared with
a
guarenteed 30mins from the local firm. However, more worrying is that
he
told me I couldn't expect more than a drop of 10 to 12 degrees -
implying
around 15C at 25ambient..

My measurements:
Ambient 25C (reading 23C at vent with fan on full, aircon on ECO (off))
Vent temperature at 2000 rpm with aircon on and running fan full - 12C
Vent temperature at 2000 rpm with aircon on and running fan minimum -
4C

So it sounds like it's cooling to 4C, but at minimum fan, the car will
never
get cool.

Plus - the compressor is making a bit of a din, so probably needs
relube
anyway?

What should I expect?

Rich
(PS - Service schedule shows a regas 2 years ago)

 

It sound like your air conditioning system is pretty well running OK if it
can get down to 4 degrees at the centre vents. The slower the fan speed the
cooler the output as air is passing through the system at a slower rate
hence receives more cooling. The system is not designed to go any lower in
temp to prevent the possibility of icing and the danger of frost bite to
fingers etc. Typically on the fully automatic climate control system it
starts out with the fan running fast to expel hot air then slows down and
output gets cooler. What a lot of air con places do is run the car at fast
idle for 10 minutes with all the vents closed except the centre pair. Then
if the gas pressure (high and low side) is OK and output has got to at least
5 degrees on a low moderate fan speed they declare the system OK.
All that said I don't think that the Omega's air conditioning climate
control system is a particularly efficent one if you like it really cold, OK
but not the best. BMW 5 series much better. It may be worth getting the gas
pressure checked but you could end up spending quite a bit of money on
having a regas only to find very maginal improvement. The system will also
lose effectiveness as componants such as the Condensor age and become less
efficent just like a radiator, although your Omega is a late model so should
still be in top shape. If the Compressor is noisy this would be worth
checking out but here things really could start getting expensive.
Unfortuneatly Vehicle Air Conditioning is an area of the motor trade thats
getting increasingly polluted with cowboys who have spotted a nice little
earner. They can top up the gas but do absolutely nothing else. I would
choose carefully where you take your car.
Hope this helps - Mark

 

a couple of things here to maybe help & clarify aircon

the outside temp should have little effect on the internal temp your get.
[as long as you are sure you are recirculation the internal air, not
bringing in air from outside.

one of the quickest ways to fruke your aircon is to make it deal with
removing the hot air inside the car first.
if your climate allows and inside is hotter than out, open the windows and
blow it out without the aircon on.
then put the aircon on recalculate with all the windows closed [i know this
is obvious - but you'd be surprised by some peoples actions!]

if you don't follow the above the moisture in the air will contaminate the
system very quickly reducing it good.

get one of the air con bombs from halfords or WHY and do that
it will make a large difference.

lastly about your eventual temp.....
4C is good, but I'd expect that on IDLE not by revving the beasty after
about 15mins.

and yes I'd agree with the other gent, there are lots of cowboys about
the evacuation of the system is one of the most important bits
many many cowboys cut this to a min to get more punters in.

mike

 

....yes but cooling outside air is a good test for the heat pumping
capability of the system. If it's 25 outside, I'd be looking for at least
single figures from the face vents at full fan speed, possibly with very
slightly increased revs from tickover

Hot humid air at the evaporator will not harm your system, just increase the
load on it. AC is designed to remove heat and humidy from air. A system
without major faults already will not absorb moisture (into the refrigerant)
from the air being cooled.

But cooling outside air is certainly the best way to get the temp down
faster if the car has been closed and in sunlight.

Probably worse than getting a cowboy to look at it - adding gas without
knowing how much is in there and without being able to properly measure the
pressures IS a very good way to wreck your system.


The temp achieved is limited by 2 factors:

1. The cooling capacity, if this is the limiting factor
2. If not, the actions of the de-ice stat and the expansion valve.

The temp at the evaporator must not approach freezing, the temp at the vents
will be a few degrees above. If you get 3 at the vents, I'd be wanting to
check that the de-ice stat is actually working.

A very good vacuum (compared to an edequate one) before gassing will
influence cooling capacity and reliability slightly, but once you get to a
few degrees, it's more likely to be the de-ice atat and expansion valve
which determine the temp.


www.poolecool.co.uk

 

what i meant here was the cleaning bomb, not the regas.. like you.. they are
worse than a cowboy!

i'm interested to see you say that cooling external air is better.
we were taught that once you have removed the hot air inside, then set the
system to recirculate internal air, this will then make it cooler & cooler
to single figures without making the system have to deal with the excessive
initial internal air or hot air from outside.

any how
i was hoping you would answer his Q
i always like you posts.
very imformative.

mike

 

....basically you want the coldest air available going into the evaporator.
If the air outside is colder than the air inside, set to normal outside air.
If the air inside is colder than the air outside, set to recirc.

This would normally mean starting with outside air, then changing to recirc
once the cabin temp has lowered.

But, when you're testing a/c, you want to make it difficult for the a/c, not
easy. I normally set on recirc and full heat, then see how quickly and how
far the temp drops when you take the heat off.


www.poolecool.co.uk

 

yep that makes sense under a test situation.
should have thought about it a bit longer.
though i will be honest andsay its only a recent addition to my teaching
knowledge at work
but we do have all the kit
it's great to learn little tips from trade users/techs

thanks again

mike