Ben8jam

I've had the card about 1.5 years. The AC blew meh cold in the spring of last year but it was pretty useless during the summer. Now that we're coming back into summer I really want some cold AC. But before I go down a rabbit hole of checking, pressures and ambient air, and from what I've read on other posts, not a lot of conclusive results that those bring, wanted to know if it's worth the time.

I do have the black foam in vents issue so I'm almost positive the blend doors are shot.

Is there any harm in trying to just add a can of refrigerant and see what happens? I can hear my AC condenser turn on. I've cleaned out all the gunk from my bumper radiators. The cap from the low-side (refill port) is missing, so I wonder if any refrigerant has been leaking from there.

I don't have a gauge for the high-side, just a low-side gauge and can puncture adapter. So before I start buying stuff, want to know if it's worth it. Most posts end in "go see an AC mechanic".

996C438

If it were me I would sacrifice a can or two of refrigerant to see what happens . And get a cap on that fitting . Schrader valves can leak the cap is a secondary protection . Whatever you do please don't add stop leak goop to the system . If you have a leak fix it right .

allcool

First thing to do is see how much, if any, Freon is still in the system.

Put your low side gauge on, see how much psi is there with engine off. Depending on your region/ambient°, should have somewhere around 70 psi on gauge this time of year if you haven't leaked it all out.
If there is pressure in system then try the next step. Start engine. Make sure compressor is running, ac set to hi fan and lowest temp setting. see what psi is at idle, if you have over 25 psi, bring rpm up to 2500 and recheck low side psi. Report back what you find.

Paul Waterloo

Just watch a few youtube videos on how to fill your system, sounds like you have a slow leak.

If it lasts 3 months, then you will have to find the location of the leak and fix it, or have somebody fix it for you. At that point you completely evacuate the system and charge the proper amount.

I would get one of the "AC Pro's" bottles, somebody I know just bought one and it even bluetooths to your phone and gives you a lot more info for people who have not done this before. I don't think it's more than $50.

Best of luck.

Ben8jam

Well off to good start... I hooked up low side gauge, and didn't have the valve on other end fully close, so vented the system right from the start (this is why we wear protective equipment!) I yanked it right now, but now after closing it the gauge reads 15psi. I don't know how much I vented, or how fast it loses pressure, so I can't say now what it was to start.

I then started car, ran at idle and rev'd to 2500 and the gauge never moved (video recorded it). When turning on AC, the engine drags so I know the compressor is kicking in. And both radiators are blowing in front when AC is on.

So, 15 is obviously low, but how fast it lose pressure I can't tell you. Does the lack of it changing PSI mean anything? It's chilly out here today, under 60F.

Ben8jam

Yeh, I saw those, but figured a dedicated gauge, and a can from AZ, would be cheaper, and I just like analogue over digital.

DBJoe996

AC is not something you really want to mess with. After 20 plus years (my car 7/98 so still on factory fill), last summer my AC was cool but not cold. I contemplated the same thing...just get a can of refrigerant from the auto parts store and put it in...but then I read up on it some more and decided to book an appointment for an AC professional with the proper equipment. He was well versed in British/American/Porsche cars. He hooked it up to his machine, evacuated the system, then filled it with nitrogen and pressure tested it for 30 minutes. No leaks. While it was still hooked up, he filled with proper amount of refrigerant AND oil for the compressor. Also added a very small amount of UV dye so in the future, if a leak occurs it will be simple to find. The AC blows freezing cold air now. And, all my foam blew out the vents 15 years ago and I never did anything about it except clean it up. Finally stopped. All in for the AC professional...$133. It was well worth it. Best thing was I got to spend a little over an hour looking at all the cool cars he had in the shop, from old MG's to Ferrari's to some exotics. I also was able to bend his ear over all kinds of stuff during that time.

I do all of my own DIY work on the car, but AC is best left to a knowledgeable professional.

https://rennlist.com/forums/996-foru...-recharge.html

Ben8jam

Yeh, that's kinda exactly what I'm thinking. If these initial tests yield inconclusive results, just gotta find the right indy, who wants to do a quick job. Everyone is so focused on big service work now with their bookings backing up. "No I don't need a new clutch with my AC refill"

allcool

Well, at 15psi on cold car at 60°ambient, you've got a leak for sure, maybe not a massive leak or it would be at 0. But a considerable one never the less.
Reason psi doesn't change when engine running, is the low pressure switch won't engage the compressor clutch @ 15psi.

Couple of options.
1)Bring it to a pro and pay.
2)Or since you do still have some pressure in the system, try dumping in a can of r134a with leak detector dye in the can. And 1 can of 134 with oil charge would also be nice. Finish your charge with the oil/freon can. iirr it takes around 2lbs 134.

Charge slowly with all windows open, ac on hi fan and set to lowest temp, on a warmer day if possible. Charge slow, being so low on freon the clutch will kick out from low pressure switch till you get the charge up in operating range. You'll hear it and see on the gauges when the compressor kicks in, keep dumping in freon till it kicks in.
Finish Charge till a thermometer in the dash vents reads mid 40°.

Run it and see how long the charge lasts for. Once it leaks out you should be able to see the leaked dye at the point of the leak. Might be surprised, could last for many months, or not.

Once you find the leak you can do it right. Fix the leak, might only be a o-ring, or could be the compressor seal, evaporator coils, condenser coils, x-valve, or piping. The dye should eventually tell you exactly what is leaking... Once the leak is fixed, change out the drier, see if you can borrow/rent a vac pump and gauges. Some auto parts stores loan/rent vac pumps & gauges out. .

Vac it down for at least an hour to remove any moisture, shut off gauges tight and make sure all hose connections are very tight. Leave system in a vac and make sure it holds vacuum. Then re-charge it the same way with correct amount of 134.

theprf

Do not EVER put A/C leak sealer in this car, or any car for that matter.
The easiest way to get an estimate in if the A/C is charged is to do this: (works best when it's hot out)
Run engine.
Doors open.
A/C on MAX cold, fresh air (not recirculate)
Blower on MAX
Rev it up to 1500 or 1800 for a minute or two
Feel suction pipe into compressor. This is the larger of the 2 pipes. It should be cold. If so refrigerant level is probably OK.

Ben8jam

So I tried to refill today. I ran the engine with the AC on max. Hooked up the gauge with the 12oz can of 134. Slowly released the valve and let the system refill. However, it went from 15 psi to 40 psi in a few minutes, but the can of 134 still feels very full.

And the AC still doesn't blow cold. I do hear the engine drop when the AC is turned on.

Any ideas? (I forgot to check the pipe into the compressor to see if it felt cold or not)

allcool

What is the idle low side pressure, what is 2500rpm low side pressure..? What is ambient temp there..?

theprf

If the gauge is only showing low side pressure you will be completely in the dark. That said, the variable compressor and thermal expansion valve setup on these cars will (should) keep the low side pressure around 40 PSI unless the system is completely empty. Since you saw 15 PSI when staring I would assume the system was almost completely empty. Hate to say it but you should use a sniffer to find the leak and fix it. I would suspect the condenser(s). Look for oily spots on the condenser fins.

General rules for R134a A/C systems using a thermal expansion valve and variable compressor: low side should be about 40 PSI, high side should be ambient temperature multiplied by 2 or 3. The pressures don't tell the state of charge on this type of system - really need to either start empty and add the correct weight of refrigerant or use the temperature of the compressor suction to see how full it is.

Ben8jam

Ok I should probably not be doing this as I'm still not clear what is to be expected in terms of pressures, and have read so far that it's not really a good indication of a working system.

Pulled car into sun. 75F outside. Connected gauge and 134 can in OFF. Turned on car, brought it up a little bit in temp at 1500rpm (hate idling the car). Pressure on gauge was at 30ish pis. Turned on AC full blast heard the Engine engage. Went and opened valve and let 134 slowly flow. It held the 30psi mark. Continued to allow it to flow and rev'd engine and recorded gauge but didn't see it do much.

Got almost all the 134 in and did start to feel the AC get cold. Switched off car, but then the gauge started to go into the red up to 80. Freaked out cause I realize i have no idea what this all means.

Now i am at a total loss of what to do. Have I over filled the system? Why does it sky rocket after the car is turned off?

On compressor side, small tube is hot, large tube is cool (as in not hot) but not cold.

Ben8jam

Idle was 30. Revving it maybe got to 35? Ambient is 75F (I pulled car out of garage into sun). See notes above as well.

If you're filling from a can, How do you know when to STOP? This is what I don't understand... Looking a chart online, 75F should equal 40-45 psi (but I just want to confirm that). And make sure that when car is off, the 80 psi I was seeing is not some danger zone....