aca6c5

I searched around and couldnt find a definitive answer on where the tube is located. Can anyone help? or have any pics?

Huskerbob

What is this orifice tube of which you speak? Could it be the condensate drain?

jcman

The orifice tube is just before the evaporator forward of the mechanical block connection in the high side line "smaller line", loosen the compression block bolts after you evacuate the system and look in the line for a plastic centered tab "orifice tube" that can be pulled out with a pair of needle nosed pliers.

Note: Not all models use a restrictor aka orifice tube some use txv's aka thermal expansion valves.

It would be very rare to replace a OT unless the mesh screen is slammed with debris that can be cleaned and reinstalled, on the other hand if you do have a txv the only reason to replace it would be a dead power element that drives the valve to keep the relative super-heat in line with the heat load of the evaporator.

Why do you think the OT is your problem?

twentysevenlitres

Husker,
The orifice tube controls pressure between the high and low pressure sides of the airconditioner gas lines.
It's a very simple filtered restriction.
In your A4, it will be under the battery and is the cause of the "shooshing" sound you hear when you shut down the car after driving with the aircon running (gas pressure equalising through the orrifice tube).

SloopJohnB@mac.com

Volvos had an orifice tube with a five- segment filter just ahead of it. After 10 years I had the shop pull my drier and replace that little filter....4 of five segments were semi clogged but the AC worked well. After replacing the filter and drier, suck and charge...it worked like a new car with about 38F coming out the vent. Point is that all compressors wear and stuff gets in the system...dunno if OP's system has more than usual, but if his hi-lo pressures indicate his orifice tube or pressure valve is clogged it generally needs to be replaced and the system flushed before that. Replace the drier too...

Huskerbob

Sweet. I learn something new every day. Never heard of that before. Thanks.

jcman

If POE or PAG oil becomes moisture laden sludge will slam the drier and metering devise, the mesh screen can be cleaned with a solvent dip and compressed air, agreed the drier should be replaced if this is the case.

Along with a blown-out compressor one of the most nasty conditions is metal debris jamming the condenser coil causing a pressure drop "system restriction" even after a drier change, I have had to liquid flush backed with compressed air in a reverse method flow to dislodge debris from the entering header of the coil "broken reed valves".

But at this point we don't know what the OP's problem is.

aca6c5

Well seeing that I have to evacuate the system I might just skip replacing the OT. The reason why I was looking @ replacing the tube was due to when the A/C is on, the air doesnt feel as cool. Sure I could just add some more refrigerant but I saw an article that a clogged OT can cause the same behaviour. When the temps are over 95degrees the HVAC is set @ 72 and the air is not as cool as if its 80degrees out.

aca6c5

Also this applies to my 01 A6 avant 2.8

jcman

You might be surprised how much road dirt is in the condenser coil fins, I use purple power and a water hose rinse on mine every two years. As with any refrigeration system it becomes very hard to condense freon over 90 degrees as the capacity drops off hence heat rejection in a rated time frame, "we are not making an area cold we are removing heat from an area"