Recharge A/C procedure

[alvocado]

I'm not sure which category this should go in but since it's in the engine bay, I'll post here.

I'm going to attempt to recharge the A/C after having the rear heat refrigerant line open to replace a leaking section. The system is completely empty so it will need a full charge of 2.5lbs.

I plan to pick up a loaner manifold guage set and vac pump from a local autoparts store along with four 12 oz cans of r134a. I've never charged a system and would appreciate any advice from those with experience, watchouts, tips, etc.

I assume that once the system is vacuumed down for at least an hour and confirmed to hold the vacuum, the next step is to connect to the refrigerant can and let it draw until the vacuum drops. At that point, do I turn the car and A/C on to continue filling until all 2.5lbs have been filled?

I would typically let a shop do this but the replacement line I installed was defective and wouldn't hold pressure. it's been in twice before getting a replacement line and I'm looking at another $260 to take it in a 3rd time on top of shop charges for the past two visits.

 

[kbuskill]

Sounds like you have it pretty well figured out.

I usually pull a vacuum for at least 30 mins and then close the valves on the manifold and shut off the vacuum pump and then let it sit for about another 30 mins and make sure it is still holding the vacuum afterwards.

If all checks out you can connect your can of refrigerant to your gauge manifold and purge the air out of the charge line before opening the low pressure valve to start chargingthe system. Don't forget to purge this line everytime you change to a new can.

Only charge through the low pressure side, never the high pressure side.

It may or may not take a whole can without starting the vehicle and turning the A/C on MAX. Run the A/C wide open for the front and rear unit and roll all your windows down while doing it.

The hardest part is measuring in the proper amount of freon. The first three full cans is a no brainer, it is the last can that you have to start watching the gauges so you don't over charge the system.

The proper reading on the gauges will be dependant on ambient temperature, but I'm sure you probably know that already.

 

[alvocado]

Thanks for tips. Should the vacuum pull a full 30 in mercury? I’m maxing out around 22. Considering I’ve been struggling to get the replacement line tight, I want to rule out an ongoing issue.

 

[kbuskill]

Thanks for tips. Should the vacuum pull a full 30 in mercury? I’m maxing out around 22. Considering I’ve been struggling to get the replacement line tight, I want to rule out an ongoing issue.

Hard to say, depends on how accurate your gauges are.

As long as the vacuum holds for a while after the pump is off you should be good.

I have seen where you can have a leak under pressure but not under vacuum but that is pretty rare. Some people will charge with something like nitrogen and see if it holds pressure but this is only usually done if there is an ongoing leak that doesn't show up with vacuum.

 

[alvocado]

The system is not holding vacuum and the issue continues to be at the rear section that was replaced. For background, the replacement fitting leaked the first time because the ferrule didn't seat. Auto Cooling Solutions sent a replacement ferrule which seated onto the tubing but I still had a leak. I then tried a replacement hose and can't get a seal. I'm running out of room to cut the tubing more to allow installation of a new ferrule and compression nut and if I did cut it back, my current replacement hose will not be long enough.

I see a nut at the retaining plate on top that holds the inlet and outlet refrigerant lines. If I remove that nut and plate, what is sealing the tubing where it goes in?

I think my options are 1) source a salvage rear A/C line and use the longer tubing section to get a new ferrule and compression nut on, 2) find a comparable GM tubing section that I can cut and will also insert into the top section, 3) see if a local hydraulics shop could fab up a tubing section, 4) remove the tubing and cut the straight section, order a longer hose.

I've been fussing with this for 2 weeks, had the truck in a shop twice to recharge and paid for shop time because the repair part is leaking, and am beyond frustrated.

 

[alvocado]

Here's the game plan: I ordered a longer, 24" replacement hose from Auto Cooling Solutions. I'll remove the low side tubing from the block, cut off the elbow then install the compression fitting out of the vehicle on that end. After some research, I'll plan to use some thread lubricant to hopefully get a leak free connection. I'll cut the other end under the truck and install a new nut and ferrule. I'll be out $50 for the second hose but it seems like the best option before looking at a complete replacement kit from ACS which runs almost $400. Will report back after the new hose arrives.

 

[kbuskill]

Here's the game plan: I ordered a longer, 24" replacement hose from Auto Cooling Solutions. I'll remove the low side tubing from the block, cut off the elbow then install the compression fitting out of the vehicle on that end. After some research, I'll plan to use some thread lubricant to hopefully get a leak free connection. I'll cut the other end under the truck and install a new nut and ferrule. I'll be out $50 for the second hose but it seems like the best option before looking at a complete replacement kit from ACS which runs almost $400. Will report back after the new hose arrives.

Just saw this, and assume you already figured it out but, if you remove that nut in between the two metal lines where it bolts to the expansion valve you will find O-rings on both of the pipes that are replaceable.

Hopefully your new plan works out and you have better luck. It sucks chasing your tail trying to fix a problem.

 

[alvocado]

Thanks for confirming. New part arrives today and I'm hoping to take a crack at it tonight. I assume those orings are HNBR so I can swap in new seals before reattaching.

 

[alvocado]

No luck after trying the 3rd hose. I have tightened down the compression nuts as hard as I can and I still see water sprayed on the tubing weep into the back of the nut when I'm pulling vaccum and the system will not hold vaccum with the pump off. It's a very slight leak but not sealed.

I couldn't get the AC line off because the steel mounting stud seems to have rusted to the aluminum plate. I was able to bend the tubing to cut off the elbow but I'm out of length to cut it again.

This company does make a kit that replaces the entire line from the rear to the compressor. I'd still have to find a way to get the factory lines disconnected and deal with the rusted stud or perhaps the plate is just sticking because it has never been off. I didn't want to chance damaging it before getting the line installed but that may not matter at this point.

 

[j91z28d1]

what kinda compression fitting is that? do you have to flare the tuning or anything?

oh and how are you cutting the tuning? I tried using a splice type fitting on a different car years ago, it would seal enough I had to add a can of 134 yearly back when it was cheap. but I got the feeling my pipe was never perfect round after cutting it.

 

[j91z28d1]

oh and I found these guys

Auto AC Parts | Automotive Air Conditioning Parts - ACKits.com https://share.google/NyHEDEIPdpS1Hm3xV

and their forum an excellent place to ask ac questions

Automotive Air Conditioning Information Forum - Index page https://share.google/coovBKvcnb1teAuTO

it's been a few years since I logged in and looked around, but was a great resource for stuff like this, guys having first hand knowledge of fixing stuff.

 

[alvocado]

Here’s a pic of the two ends I cut off today with a tubing cutter.

 

[j91z28d1]

I've not seen that type of fitting. what's the hose side look like?

I've only used one like this with rubber seals too.

 

[alvocado]

It’s a standard compression fitting just like those used in plumbing applications. Here’s a pic of the hose.

 

[j91z28d1]

I was just wondered what this hose side fitting looked like before it was screwed together.




from the outside it looked like a standard AN style fitting with the 37deg or whatever it is cone. but that wouldn't fit with the other side at all, so was just curious what you're working with. not that you're doing anything wrong or anything.

 

[alvocado]

 

[j91z28d1]

that sure looks like it should seal as long as the aluminum pipe is clean and smooth. have you tried putting some postive pressure in the system? maybe you have a leak someplace else?

 

[alvocado]

I’ve had it in the shop twice to recharge and it’s leaked out the new hose fitting both times. I can see water wicking into the fitting when I’m pulling vacuum so at a minimum, this is a leak point. The factory hose to metal connection was originally leaking which started this saga.

 

[j91z28d1]

I’ve had it in the shop twice to recharge and it’s leaked out the new hose fitting both times. I can see water wicking into the fitting when I’m pulling vacuum so at a minimum, this is a leak point. The factory hose to metal connection was originally leaking which started this saga.

Damn man, I hope you get it sorted.

 

[alvocado]

Me too!