AC won't take freon

[suprasvobodea]

I’ve seen plenty of systems that will hold pressure but not a vacuum. Usually due to either a bad o-ring or improperly installed one. Same can happen to compressor shaft seals. When it comes to refrigerant systems and o-ring sealing performance, things really must be surgically clean. Always coat the o-rings with the appropriate compressor oil during installation.

Canman

Thank you for the reply. I wrote a detailed response to Flintknapper , as to my next steps. When Im done, I decided I'm going to get a used set of GOOD gages and a GOOD used vacumn pump with at least 2.8 CFM ( this one is 1.7CFM i think) or >> to have for future use. The seals on both the high,low, and yellow lines are smushed, crushed, or distorted - like someone said previously. Please feel free to add anything you think I should do.

 

[suprasvobodea]

So many unknowns here.

Please disregard the Youtube videos, often times they are not a good source for information with respect to Automotive A/C work.

At your elevation (Dallas) you should be able to achieve at least 28 inHg vacuum with a fully sealed system AND a good vacuum pump.

Rental pumps run the gamut from being good/usable equipment to worn out junk. Quite possible the vacuum pump itself won't let you get a deep vacuum on the system. IF the pump was a single stage type, worn...and did not have NEW/Fresh oil in it....then that is part of the problem right there.

System leaks are another possibility. While you replaced the Compressor, Condenser and Dryer....we don't know the condition of the Evaporator. It is not uncommon to have a small leak in the bottom corner of an evaporator. Typically debris collects in the bottom of the housing and gets soaked with the condensation produced there... leaving the bottom of the Evaporator sitting in mix of wet gunk. Naturally... this corrodes a spot in the Evap that usually presents as a small leak.

Until we know one way or the other whether the system is leaking (or not) it doesn't make good sense to go forward. Since some leaks can be difficult for the DIYer to find and address.....I would recommend (in this case) you take the vehicle to a reputable shop, tell them what you've done so far as see what they can find.

At that point....you can decide to let them do the work or take it back home and continue. IF the system will hold a vacuum then there is no reason why you can't charge the system yourself....BUT we still have a couple of unknowns (Condition of the Evaporator and TXV if so equipped). Hate to have you go through all the work only to end up with mediocre vent temps.

You bring up a good point about Evaporator. What are the symptoms of a bad or plugged evaporator valve? I know if the pressure are equal, is an obvious one. Also, I know the evap. located in the passenger footwell, & have NOT looked at or removed it - since it's usually not a part that fails, since it's inside the cabin. My question>> If the shop finds and repairs the leak tomorrow, do I have to remove and flush that too ? I really don't want to, deal with it too.

 

[suprasvobodea]

I’m a mechanical engineer with over a decade of experience with mobile HVAC. The system will take the refrigerant charge at 24” HG since the pressure in the refrigerant container will be roughly equivalent to the ambient temp in F. As you mentioned, unless you can achieve and maintain a vacuum of 29” HG, you have a leak, and there is no point in adding any refrigerant as it will eventually leak out.

I am also a BSME! However, I am an Aerospace design engineer- structures /, Project Manager. ( not an HVAC guy) However, I have been on a steep learning curve with regard to automotive HVAC components, diagnosis, and repair,... and I enjoy learning new skills and systems ( all self-taught!)

 

[gummycarbs]

What are the symptoms of a bad or plugged evaporator valve?

I can't imagine going to all the trouble of evacuating an AC system and *not* replacing the TXV. And if you haven't removed your evaporator to clean and inspect it, boy are you in for a surprise.

 

[canman]

I am also a BSME! However, I am an Aerospace design engineer- structures /, Project Manager. ( not an HVAC guy) However, I have been on a steep learning curve with regard to automotive HVAC components, diagnosis, and repair,... and I enjoy learning new skills and systems ( all self-taught!)

Haha! If I could do it over, I think I would have chosen aerospace. All I do now is push papers and coral PMs in our PM Support Office for the military.

 

[canman]

Canman

Thank you for the reply. I wrote a detailed response to Flintknapper , as to my next steps. When Im done, I decided I'm going to get a used set of GOOD gages and a GOOD used vacumn pump with at least 2.8 CFM ( this one is 1.7CFM i think) or >> to have for future use. The seals on both the high,low, and yellow lines are smushed, crushed, or distorted - like someone said previously. Please feel free to add anything you think I should do.

Yeah, the cheaper manifold gages can have issues with the seals, but they usually come with a couple spares. The trick is to avoid tightening them too much as the seals are fairly soft. The trick with using the manifold gages is knowing when and what order to open/ close them when charging/evacuating making sure no air is present, and being mindful if refrigerant is still in the line(s). If you get a used pump make sure you get fresh oil and replace the oil in it as it may be contaminated with moisture. If the oil is contaminated with excessive moisture, it will give a false impression that you can’t pull a proper vacuum on the system as it continually boils off that moisture in the oil.

 

[suprasvobodea]

Yeah, the cheaper manifold gages can have issues with the seals, but they usually come with a couple spares. The trick is to avoid tightening them too much as the seals are fairly soft. The trick with using the manifold gages is knowing when and what order to open/ close them when charging/evacuating making sure no air is present, and being mindful if refrigerant is still in the line(s). If you get a used pump make sure you get fresh oil and replace the oil in it as it may be contaminated with moisture. If the oil is contaminated with excessive moisture, it will give a false impression that you can’t pull a proper vacuum on the system as it continually boils off that moisture in the oil.

Oh, I didn't know that the oil has the ability to become saturated with moisture !?!? I can see the oil in the pump thru the glass panel and it's very clear and looks like new oil. !! I didnt change it, but I could ADD some new.... I'm curious.... why does " old " oil, not function as intended and lubricate the vacuum pump ???

 

[canman]

Oh, I didn't know that the oil has the ability to become saturated with moisture !?!? I can see the oil in the pump thru the glass panel and it's very clear and looks like new oil. !! I didnt change it, but I could ADD some new.... I'm curious.... why does " old " oil, not function as intended and lubricate the vacuum pump ???

Some good info here.

https://fjcinc.com/importance-of-checking-and-changing-vacuum-pump-oil/

 

[gummycarbs]

I didnt change it, but I could ADD some new.... I'm curious.... why does " old " oil, not function as intended and lubricate the vacuum pump ???

If you do any reading about AC systems, you'll see warnings to replace vacuum pump oil after every use.

I'm going to be a bit rude here and tell you that you're in way over your head. You might be an engineer, but you seem to have not done even *basic* reading about AC system maintenance. You need to stop messing with your system and leave it to the professionals before you cause serious damage.

 

[flintknapper]

Oh, I didn't know that the oil has the ability to become saturated with moisture !?!? I can see the oil in the pump thru the glass panel and it's very clear and looks like new oil. !! I didnt change it, but I could ADD some new.... I'm curious.... why does " old " oil, not function as intended and lubricate the vacuum pump ???

Vacuum pump oil not only lubricates the pump but also captures moisture and contaminants. Think of it as a blotter that can become saturated. Vacuum pump oil is highly refined oil and has a low Vapor Pressure. It needs to be fresh in order to capture contaminants and enable your pump to work at peak efficiency.

 

[suprasvobodea]

So many unknowns here.

Please disregard the Youtube videos, often times they are not a good source for information with respect to Automotive A/C work.

At your elevation (Dallas) you should be able to achieve at least 28 inHg vacuum with a fully sealed system AND a good vacuum pump.

Rental pumps run the gamut from being good/usable equipment to worn out junk. Quite possible the vacuum pump itself won't let you get a deep vacuum on the system. IF the pump was a single stage type, worn...and did not have NEW/Fresh oil in it....then that is part of the problem right there.

System leaks are another possibility. While you replaced the Compressor, Condenser and Dryer....we don't know the condition of the Evaporator. It is not uncommon to have a small leak in the bottom corner of an evaporator. Typically debris collects in the bottom of the housing and gets soaked with the condensation produced there... leaving the bottom of the Evaporator sitting in mix of wet gunk. Naturally... this corrodes a spot in the Evap that usually presents as a small leak.

Until we know one way or the other whether the system is leaking (or not) it doesn't make good sense to go forward. Since some leaks can be difficult for the DIYer to find and address.....I would recommend (in this case) you take the vehicle to a reputable shop, tell them what you've done so far as see what they can find.

At that point....you can decide to let them do the work or take it back home and continue. IF the system will hold a vacuum then there is no reason why you can't charge the system yourself....BUT we still have a couple of unknowns (Condition of the Evaporator and TXV if so equipped). Hate to have you go through all the work only to end up with mediocre vent temps.

**UPDATE ***

I did take it to a mechanic to have them add the freon, but they did a s***ty job and did NOT fix the leak!!!! ( THERE FOR THE NEXT PARAGRAM IS A SELF-TAUGHT LESSON!== learn or teach yourself to do this job@@! It not only saves you $$ thousands of dollars but it will be done RIGHT! ) I bought my own gauge and vacuum pump so now I have new equipment that I know is working and not leaking in the seals in the fittings!

It's now Aug 2023 and its frickin 110 F now in Dallas !!!
I am back on the 87 SUPRA and have taught myself several new things about auto AC systems! First, I removed the evaporator and inspected it. I replaced the expansion valve with a new DENSO one as well. The evaporator had no leaks. I bought a can of AC flush and flushed out all the old oil, dye, and whatever else settled in the low spots. I rolled it several times to wash all the coiled passages with the fluid to wash it out thoroughly.
After doing all that, I reinstalled it back inside the Supra and tightened down the high and low pressure fitting at the firewall in the engine bay. The low side ( Large tube) fitting was not tightening completely so I untighted it and inspected the threaded tube. end of the evaporator. With my luck, the last 3 threads had SPLIT off the tube and needed to be cut off. That meant REMOVING the evaporator again ( 4th time! ) and taking a hack saw to remove them. However, when I inspected the threads, the fitting had somehow got CROSS THREADED, and the remaining threads on the low-pressure tube were ruined, The only solution was to order a New EVAPORATOR. Probably a good idea as now EVERYTHING in this AC system is new! I'm still waiting for a DENSO evap to come in. Now that I know how to add freon in a liquid state through the HIgh side, ai will do that first ( with the compressor off of course !) and then add 2nd can as gas.

 

[suprasvobodea]

UPDATE to Update - 8-28-23

The DENSON evaporator came in and installed it! I did as Flintnapper suggested and did the 1st can as a liquid. It went, in 2 min! Then I added 10 oz on the scale to in LOW side from 2nd can and .....

It's BLOWING COLD AIR, NO leaks, AND WORKING perfectly !!! I figure I saved over $1200 + for a new system. Now I wish I had saved the old R12 s Shrader valves so I could reinstall them BACK to the original system. I actually have several cans of R12 !!! This R134a does NOT work in this system like the R12. Its about 70% less efficient in temp here in Dallas TX .

 

[flintknapper]

UPDATE to Update - 8-28-23

The DENSON evaporator came in and installed it! I did as Flintnapper suggested and did the 1st can as a liquid. It went, in 2 min! Then I added 10 oz on the scale to in LOW side from 2nd can and .....

It's BLOWING COLD AIR, NO leaks, AND WORKING perfectly !!! I figure I saved over $1200 + for a new system. Now I wish I had saved the old R12 s Shrader valves so I could reinstall them BACK to the original system. I actually have several cans of R12 !!! This R134a does NOT work in this system like the R12. Its about 70% less efficient in temp here in Dallas TX .

Good Job!

Yes, I'd prefer to have a good working R12 system over a R134a (here in Texas). But R134a can make a reasonable system in an 80 series.

It was 108°F yesterday. I was able to maintain 50°F vent temps (which felt plenty good enough) but I have my A/C system dialed in for best performance and also run a 12" Derale High Output condenser (Aux) fan.

 

[suprasvobodea]

Sounds like a bad vacuum pump (or pump connection) or a seal that only seals under pressure.

IT was!! I bought my own pump and gages on Amazon for $220 for everything. Now I have good operating equipment and NEVER have to rely on AUTOZONE again for anything AC-related. ( except 134a!)

 

[shocktower]

OK I have a functional AC and everything what you told me didn't solve my problem, but I did a little poking around and found out the Tem shut off switch was the problem so when I unplugged it my clutch engaged and I've got cold air I know it's been a while since I asked but I figured it out