A/C liquid line

[Fish302]

Hello everyone! I bought a 91 Plus model six months ago, 188k miles. The car sat for quite some time with no charge in the A/C system and i recharged it after putting it under a vacuum and it worked flawlessly until yesterday. I have a blockage on the low side, I fear the desiccant pouch in the receiver/dryer broke. Where is my orifice tube located? I can't even find the liquid line at the firewall, I can only see the low (vapor) line. I need to get the screen out to see just what kind of hate and discontent I'm going to deal with

 

[NoSlo]

Do you have simultaneous pressure readings from the hi and lo ports? A plugged orifice tube or filter causes very fast and high high-side pressure and low low-side, even changing from low pressure to vacuum on the low port if the cycling switch is jumpered.

The orifice is a permanent part of the condenser-to-evaporator tube (aka liquid tube). Either one replaces the whole tube, or cut 2 1/2" of the tube perfectly to replace the orifice section (crimped-looking section near front of car) with a E5VY-19D695-A orifice kit (on ebay for $15).

The liquid tube is the line up front going to the condenser without the pressure test port. The condenser is of course buried behind the radiator, and full access to see what's going on and remove the hose is to remove the radiator, drop trans cooler, and potentially bumper cover. You need spring connector disconnects, little plastic tubes that snap around the line and push into the connector.

With the tube removed, you can blast it with compressed air in reverse and see if detrius is ejected from the screens and it flows again.

There is also a filter kit (f2vy-19e773-c) that has a filter you permanently install in the line between dryer and compressor; as any debris created by dryer would hit the compressor first.

 

[Fish302]

Do you have simultaneous pressure readings from the hi and lo ports? A plugged orifice tube or filter causes very fast and high high-side pressure and low low-side, even changing from low pressure to vacuum on the low port if the cycling switch is jumpered.

The orifice is a permanent part of the condenser-to-evaporator tube (aka liquid tube). Either one replaces the whole tube, or cut 2 1/2" of the tube perfectly to replace the orifice section (crimped-looking section near front of car) with a E5VY-19D695-A orifice kit (on ebay for $15).

The liquid tube is the line up front going to the condenser without the pressure test port. The condenser is of course buried behind the radiator, and full access to see what's going on and remove the hose is to remove the radiator, drop trans cooler, and potentially bumper cover. You need spring connector disconnects, little plastic tubes that snap around the line and push into the connector.

With the tube removed, you can blast it with compressed air in reverse and see if detrius is ejected from the screens and it flows again.

There is also a filter kit (f2vy-19e773-c) that has a filter you permanently install in the line between dryer and compressor; as any debris created by dryer would hit the compressor first.

View attachment 81381

 

[Fish302]

Thank you! I figured it had to be somewhere in the mess I can't get to lol. The system reads high on the low side, if I try to add refrigerant, it immediately dead-heads

 

[NoSlo]

Thank you! I figured it had to be somewhere in the mess I can't get to lol. The system reads high on the low side, if I try to add refrigerant, it immediately dead-heads

That is the opposite symptom as is expected from orifice tube. Engine off, high and low should be equal, with the low side pressure high enough over 50psi to close the pressure switch. When running, the pressure switch on the dryer runs the compressor until the low side drops below the cutoff, and then it cycles on-and-off as pressure leaks through the orifice. When connecting a bottle with gauge (which doesn't need the "tap" to be opened on many to get a pressure reading), you should see the pressure drop from high 50+ down to 30 and back with about a 15 second cycle time on a warm day. The compressor needs to be operating properly and pulling the low side low to charge the system with a can.

If the system is over-pressurized, then the system may never go low enough to turn off the pressure switch (which is also the case when you are driving in 110 degree weather). Too much charge and the compressor is bogged down, overheating the refrigerant, until the overpressure relief valve on a 94+ blows.

If the compressor is compressing poorly, you also get a constantly-running system, but the high side never gets high enough.

 

[Fish302]

That is the opposite symptom as is expected from orifice tube. Engine off, high and low should be equal, with the low side pressure high enough over 50psi to close the pressure switch. When running, the pressure switch on the dryer runs the compressor until the low side drops below the cutoff, and then it cycles on-and-off as pressure leaks through the orifice. When connecting a bottle with gauge (which doesn't need the "tap" to be opened on many to get a pressure reading), you should see the pressure drop from high 50+ down to 30 and back with about a 15 second cycle time on a warm day. The compressor needs to be operating properly and pulling the low side low to charge the system with a can.

If the system is over-pressurized, then the system may never go low enough to turn off the pressure switch (which is also the case when you are driving in 110 degree weather). Too much charge and the compressor is bogged down, overheating the refrigerant, until the overpressure relief valve on a 94+ blows.

If the compressor is compressing poorly, you also get a constantly-running system, but the high side never gets high enough.

 

[Fish302]

Thank you! I'm working with a cheap set of gauges and a tap can. I will say that I never saw the compressor cycle once when I used the a/c, high side reading was around 150 before failure. The compressor didn't make noise or lock up, but I'm thinking I should budget for a pretty extensive rehab

 

[NoSlo]

If the system stopped working suddenly with no input, I would start with full electrical examination, pressure switch (jumper harness), CCRM, field coil voltage etc. then compressor pulley shims, and verify compressor is turning. I've typed that up several times.

 

[Fish302]

I verified the clutch is locking and the compressor is spinning. No audible noises coming from the compressor or visible slippage on the compressor hub. When I dig into this, I'll post what I find in the system.

 

[FastCAD]

Hello everyone! I bought a 91 Plus model six months ago, 188k miles. The car sat for quite some time with no charge in the A/C system and i recharged it after putting it under a vacuum and it worked flawlessly until yesterday. I have a blockage on the low side, I fear the desiccant pouch in the receiver/dryer broke. Where is my orifice tube located? I can't even find the liquid line at the firewall, I can only see the low (vapor) line. I need to get the screen out to see just what kind of hate and discontent I'm going to deal with

The liquid line w/ the integrated orifice tube is is under the battery tray running along the sub-frame to the firewall. If you are changing or have changed to 134A it would be best to cut the stock liquid line and use the mentioned "quick change adapter". I would suggest that you do a system flush it will make the results better and don't forget a new 134A recycle switch.
When I converted my '91 I switched to a high efficiency condenser to compensate for the 2% loss in cooling power from the new gas with good results.