Would like to get some clarification on how to add oil to a system when replacing just one component like the drier. Can oil be added directly to the drier? Most everything I've read says to add oil directly but wouldn't that saturate or clog the drier? I've done a lot of research and just stumbled on a post which says to evacuate, vacuum then add oil which makes sense to me but not sure how that would be done in a garage without contaminating the system with air if oil was poured into the manifold hose to be sucked in.

 

You can add the oil to the service line(yellow) on your a/c manifold gauges. Add the amount of oil and then screw on the refrigerant can. When you open the low line at the manifold it will suck in the oil already in the service line and the refrigerant.

 

Hey man! Thank -you so much for your hard work with this in depth write-up. EXELLENT!!!!!!!!

 

EXCELLENT!!!!! (I'm a dork)

 

You can add oil in two ways without a recovery machine: You can dispense it by weight into the part based on the part capacity specification, or you can draw oil in from the yellow evac/recharge line on most manifold gauge sets. Ideally, you will use a RRR machine that dispenses the oil with a control valve to prevent over-oiling. In the absence of a RRR machine, you should dispense oil by weight directly as it is much easier to control, and the oil will not move when a vacuum is drawn on it. I've seen a lot of technicians over oil trying to suck from the yellow line. It can cause the receiver or accumulator dessicant bag to rupture in some cases and lead to cooling problems later. Not to mention, it is very difficult to correct once you over-oil.

 

Hey guys, just tried helping my bro with his 2002 Civic EX A/C over the weekend. He replaced the compressor and receiver dryer, and added the proper amount of oil in the process.

So we pulled a vacuum on the system, and it held vacuum fine. Then I hooked up the can of refrigerant to the yellow hose, purged the yellow line of air, started the car, opened the low side of the gauge set, and started shaking the can side-to-side like the can directions said. Nothing. The car would not draw in any refrigerant at all. I even tried swapping ends on the yellow line (one end had a schrader valve, the other did not), and still nothing. Whenever I opened the low side on the gauge set, the low side pressure would jump to around 80-100 PSI and stay there without changing, which was obvious since no refrigerant was coming in, further verified by nothing in the sight glass between the gauge valves. High pressure side remained closed, and the needle stayed below zero (it should rise up some when the refrigerant starts coming in).

He took the car to a shop today and they said the high pressure valve was "stuck", which I'm not sure if that meant stuck open or what. I'm not sure why that would prevent the car from drawing in refrigerant through the low side valve. I kept the high side valve on the gauge set closed the whole time I had the refrigerant can connected.

Anyone ever heard of an issue like this?

 

When charging a system from a vacuumed state, or really any state, the can must be punctured by the yellow charge hose or some other can-tapping device. When this is done, and the low side valve is opened fully on the manifold gauge set AND the low side port is connected correctly and is open, refrigerant will begin to flow into the compressor, and the system. The high side port is not used during the charge process, but it can be used to monitor pressure changes in the system in the closed position.

When you hook up a manifold gauge set with both high and low side valves closed on the manifold itself, it will register the system pressures only. The high/low valves are used to remove, add, or bypass the metering device entirely if both are simultaneously open. This tactic is generally used to determine if the compressor is cycling refrigerant or not. There are three states for the valves, given that the low/high couplers are open to the manifold:

Low-side open, high-side closed: With the compressor running, this will draw refrigerant in the can into a boil, which will cause it to discharge into the system. It will also cause the can to freeze, and will delay recharging to some degree. It helps to submerse the can in warm water to keep the refrigerant boil (recharge) process alive. If the system is vacuumed in the same situation, you may get a fast clutch-cycling issues. This is because the refrigerant density is too low for the high/low pressure cutoffs. As the system takes a charge, this will stabilize. You NEVER want to invert a can on the low side of the system, this is a hydro-lock situation, and can permanently damage the compressor!

High-side open, low-side closed: With the compressor running, this can be used to remove refrigerant from the system until the pressure cutoff switches prevent compressor operation. This feature is generally not used, because it can cause the device attached to the yellow line to explode due to over-pressure.

Low-side open, high-side open: This mode bypasses the metering device and evaporator in most systems, depending on the location of the ports. This mode is generally used with no device on the yellow line, and the sight glass is used to determine if the compressor is cycling refrigerant at all. This is primarily for diagnostics on systems with a full change, and no meaningful change in low/high side pressures during operation. This mode CANNOT be used on systems with a high-side port located after the condenser, as you will be inserting liquid refrigerant into the compressor.

Modern RRR machines will remove refrigerant from the system from both sides simultaneously, and usually recharge on the low side only to prevent the on-board pump (if equipped) from fighting the compressor and damaging it. This is really an equipment-dependent process, so each RRR machine should have the reference manual handy to prevent mis-use. Older systems that require manual contamination purges are almost never done, and is the primary source of the entrance of air and other contaminants into the system. On these designs, the pressure-temperature chart must be referenced to purge air and other contamination from the fill cylinder prior to recharging. On newer systems after you enter the amount to dispense, the machine will enter a self-purge mode, where valves and pressure are released in a controlled manner.

 

Thanks, bro took the car to a shop and they said the high side valve was stuck (open? closed? I don't know), even though we were only charging (trying to charge) through the low side port. We think the hose connections on the ports were not opening the valves on the AC lines, despite being screwed down all the way into the OPEN position, and me checking that they were both fully seated. They also told him one of the lines was leaking. I don't really know any details. Apparently the whole time we were pulling a vacuum it was just in the gauge set lines themselves.

 

This is a first for me, and you should document this process and the valve replacement itself thoroughly. I have never seen a manifold gauge valve fail to open the low or high side port when fully open. This sounds to me like faulty service equipment.
Which line was leaking?

 

I don't really know any more details. We even tried 2 different gauge sets, and never could get the system to draw in any refrigerant. I've done the exact same process on 2 other cars and never had an issue, which is why it was surprising to me, also.

Then again, after pulling the vacuum and starting the engine (AC system turned on), opening the low side gauge valve would cause the gauge to spike up to 80-100 PSI, but still no refrigerant going in. Why would that happen? Seems like it was reading the pressure in the can of R134a refrigerant, instead of the pressure in the actual system. That again would point to the hose connection not opening the service port valve on the actual AC line in the car.

 

Sounds like two issues, one, your system should not operate it if truly has not refrigerant in it, it should fast-cycle as the system take up a charge, this is a low-pressure cutoff problem. This normally goes un-diagnosed by a lot of technicians.

The second issue could be that the valve is frozen in place and wont open from the outside, or your service coupler is not interfacing correctly with the port. This does happen on vehicles, even sometimes when the service port caps are correctly installed. I had to replace the condenser/receiver line on multiple Accords, including the one I own, because the port has water damage/corrosion. Usually when the damage is that bad, you can't remove the valve, only replace the line that houses it.

 

When I said AC system turned on, I meant engine running and blower fan turned on, with AC button turned on. The compressor itself was not running as we had just pulled a vacuum on the system... or so we thought. Hell it might have been a vacuum only in the gauge set lines.

Oh well, $300+ later at a shop, and now the car is fixed.

 

Hi all- I could use a bit of confirmation here. I just D.I.Y. A/C overhaul after my car experienced the dreaded black death. A/C blows cold at 39 degrees coming from the vents at idle and under load on an 80 degree day with 35% humidity. The performance seems right and I am definitely not complaining because this was significantly better than when I had the car with an ailing A/C system. I could be over thinking it but can someone confirm if my low pressure readings aren't correct and won't cause any other system failures down the road:

Idle -25psi

Under load 1500-200 rpm: drops down to 10-15psi before compressor cycles off so pressure can climb back to 50psi before kicking back on

just to confirm, at no time did my vent temperatures ever climb above 45 degrees.

 

I sincerely appreciate the assistance and support you provided on this prestigious forum.
Looking for new technical information can be intimidating, overwhelming, and downright scary. That is why it is so important to have assistance with the process especially having someone like you to help.
Thank you again for taking time out of your busy days to write down such a beautiful and informative article. Warm Regards.

 

Very helpful post

 

Great info. Saved me from making a major error. Appreciate it.

 

Nice! thank you!

 

 

While I have never disassembled a failed TXV for a noise issue, I have replaced a few dozen for making a "humming" sound.

Even if you did put in too much refrigerant,that wouldn't cause the failure. If you're certain that is the source of your noise, just replace it.

 

At 80 degrees it is undercharged, but only slightly. A half a can or less of r134a would be sufficient. Leaving it alone isn't the end of the world though

 

Does anyone have a good source for non-Honda o-rings that would replace part numbers:
80872-SN7-003 (1/2")
80871-SN7-003 (5/8")

I'm looking for options that have the same spec, but ship faster and are lower cost.