Automotive Air Conditioning Information Forum

Hi,

newb here (of course). I'm rebuilding the AC in a 1988 Toyota Pickup. I plan to replace the following components with new ones and use R134a:

condenser, compressor, evaporator, dryer, TRX valve, and o-rings will all be replaced with new units.

Truck came with factory AC but the aluminum tubing (roughly 1/4" OD) from the evaporator to the dryer was missing. I just sourced this tubing from eBay. So how can i flush this, assuming it's not installed? Can I drip solvent through it?

How do I flush the 2 lines from the compressor? These appear to be in decent shape. Or should I replace them? If replace where can I source them? If I just remove and flush, do I just drop solvent through them?

I'm confused about the process of converting the compressor to R134 (it will be new). I understand that PAG46 oil must be used, but I don't understand how the fittings are different. What tools do I need to change the fittings, and how do I source the fittings? A link would be appreciated.

Also, it seems that new compressors do not have a manifold with the fittings. I just use the manifold from the old compressor with new seals?

Finally, I plan to rebuild this system and vacuum test it to ensure no leaks. But I'm not sure I really want to go through the trouble of filling it myself. Is my plan (flush tubing, replace components and pressure test) the right approach before taking to a shop and having the system filled?

I have the Toyota service bulletin that has the oil and R134 refrigerant volumes. http://tms.cleanautoalliance.org/documents/ac002t98.pdf

Thank you!

Re the R12 to R134 fittings. Is this what I need? And what are the black ones for? And why are there two blues and two reds?

And should I install service ports in the compressor lines? One of the line appears to have a blue (low) service port. There is no red service port in the high line.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm I'm rebuilding the AC in a 1988 Toyota Pickup. I plan to replace the following components with new ones and use R134a: condenser, compressor, evaporator, dryer, TRX valve, and o-rings will all be replaced with new units.

So far, so good, but note the following: The new compressor, if it contains mineral oil, must be flushed several times with the oil you intend to use—in this instance, PAG-46. The receiver/dryer (R/D) you install must contain desiccant that's compatible with R-134a. Tim at ACKITS.com, this site's sponsor, can help with the parts and supplies you need.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm Truck came with factory AC but the aluminum tubing (roughly 1/4" OD) from the evaporator to the dryer was missing. I just sourced this tubing from eBay. So how can i flush this, assuming it's not installed? Can I drip solvent through it?

I presume that you're referring to the tubing that extends from the condenser to the R/D on the high-pressure side of the system. You don't need to flush new parts (with the possible exception of the compressor as already mentioned) unless the tubing is not sealed—that is, if it lacks plastic sealing caps on each end. If it does lack the caps, flush the line using this tool from ACKITS.com: 43-4054 A/C FLUSH CYLINDER W/GUN, plus a suitable solvent available on the same Web site.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm How do I flush the 2 lines from the compressor? These appear to be in decent shape. Or should I replace them? If replace where can I source them? If I just remove and flush, do I just drop solvent through them?

I recommend replacing them with barrier hoses if possible. The ones you have now are non-barrier hoses and might leak with R-134a. Check with Tim at ACKITS.com for availability.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm I'm confused about the process of converting the compressor to R134 (it will be new). I understand that PAG46 oil must be used, but I don't understand how the fittings are different. What tools do I need to change the fittings, and how do I source the fittings? A link would be appreciated.

As you know, the fittings on your original R-12 system differ from those for R-134a systems and must be changed. Again, contact Tim at ACKITS.com for the correct parts.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm Finally, I plan to rebuild this system and vacuum test it to ensure no leaks. But I'm not sure I really want to go through the trouble of filling it myself. Is my plan (flush tubing, replace components and pressure test) the right approach before taking to a shop and having the system filled?

A system that holds vacuum is no guarantee that it won't leak under pressure, and vice-versa. If you don't have the proper equipment and know-how to do that part of the job yourself, I recommend letting a professional shop handle the evacuation-and-charging portion for you.

murphtron wrote: ↑Wed Aug 31, 2022 12:57 pm I have the Toyota service bulletin that has the oil and R134 refrigerant volumes. http://tms.cleanautoalliance.org/documents/ac002t98.pdf

The referenced document differs from the specifications that I have for your truck, but I would go with what Toyota states. Of course, you'll substitute R-134a and PAG-46 instead of R-12 and mineral oil.

murphtron wrote: ↑Wed Aug 31, 2022 6:12 pm Re the R12 to R134 fittings. Is this what I need? And what are the black ones for? And why are there two blues and two reds?
And should I install service ports in the compressor lines? One of the line appears to have a blue (low) service port. There is no red service port in the high line.

Tim at ACKITS.com can help you with the correct adapters.

If memory serves, the high-side service port might be on the new line you're planning to install, near the R/D and sight glass assembly.

Thanks so much for the feedback! I'll contact Tim.

The parts I sourced on eBay are what's shown in this video starting at 0:32sec.

https://www.youtube.com/watch?v=OWDu8Feca8c

It's a 2-piece aluminum line that goes from the Dryer to the Evap unit. Not the short line from the Dryer to the condenser. It's used, not new. I assume I should flush it to be thorough. That make sense? That's really the only part (aside from the short line from the Dryer to the4 Condenser) which would be flushed, assuming I replace the two lines from the compressor. The rest of the system will be new.

Right, I would flush the used lines, and dry them out thoroughly. Nitrogen is best for blowing through them, but if you don't have a nitrogen set-up, shop air will do in a pinch—the drier the better. The new condenser, evaporator, and hoses don't need to be flushed as long as they're factory sealed.

I see from the video that both the high-side and low-side service ports appear to be on the hose adapters attached to the compressor. The new barrier hoses (if available) might come with the R-134a service ports. If not, you'll have to convert the fittings on the adapters from R-12 to R-134a hardware as previously discussed and, if necessary, transfer the old adapters to the new compressor. By the appearance of the plastic caps, the compressor in the video appears to already have the R-134a service ports.

If you're unfamiliar with getting the right amount of PAG oil into the system, let's discuss that as well because it's very important to the longevity of the system.

One last comment concerns the TXV. If you can get an OEM (Denso) TXV, I suggest doing so. Some aftermarket TXV's have been known to give problems over the past few years. You don't want to have to do the job all over again should a "new" TXV prove defective.

Hi again,

OK, I've sourced all of the new parts and am having new barrier hoses built with inline fill ports. I'm almost ready to re-install the system and have it evacuated and charged!

I want to follow up on the process and volume of getting PAG-46 oil into the system. I read the Toyota R12 to R134a conversion document http://tms.cleanautoalliance.org/documents/ac002t98.pdf and I think the oil volume described (100cc) assumes the system is not flushed (the process on Pages 5-6 does not describe flushing, and specifically mentions ND6 and new PAG oil will be mixed). And the 100cc in the document is to account for the reduced volume of R134a. Although I'm not certain. What is your opinion?

The new compressor contains ND6 oil. So I will drain this first and then fill with PAG-46. I should spin the wheel a few times to ensure the clutch is lubricated. Is this correct? Anything else about filling the compressor with oil?

What is the PAG-46 oil volume you have for my system? You had mentioned the Toyota document is different than what you have. Or should I stick with 100cc?

The receiver/dryer instructions say to add 20ml PAG-46 oil to the OUT side. Make sense?

All of the new components seem to be under vacuum, and I've read the receiver/dryer should be installed last. Is there an order I should install the parts? As soon as I remove the seals from the eval and condenser, air will enter the system. So does it matter? I assume the receiver/dryer is installed last as it contains a desiccant and should remain sealed for as long as possible.

Thanks again!

murphtron wrote: ↑Mon Sep 26, 2022 3:08 pm I want to follow up on the process and volume of getting PAG-46 oil into the system. I read the Toyota R12 to R134a conversion document http://tms.cleanautoalliance.org/documents/ac002t98.pdf and I think the oil volume described (100cc) assumes the system is not flushed (the process on Pages 5-6 does not describe flushing, and specifically mentions ND6 and new PAG oil will be mixed). And the 100cc in the document is to account for the reduced volume of R134a. Although I'm not certain. What is your opinion?

I never heard of mixing Mineral Oil with PAG oil as suggested in the Toyota TSB. In fact, as far as I know, mixing the two types of oil is to be carefully avoided. So right off the bat, I would disregard the TSB you referenced that suggests mixing 100 cc's (3.4 fluid ounces) of ND8 (PAG-46) with the Mineral Oil that's already in an R-12 system.

In your situation, you're starting with a completely clean and "dry" system (presuming that you fully drain the compressor), so I recommend going with the original oil-fill specification (see below). The 100cc oil spec that the TSB mentions has nothing directly to do with the amount of R-134a charged into the system.

In perusing the referenced TSB, I don't see any mention of ND6. But if you're interested in ND6 oil and what Toyota used it for, go to this Forum's archives and search for "ND6 oil" for an eye-opening post or two from 2005.

murphtron wrote: ↑Mon Sep 26, 2022 3:08 pm The new compressor contains ND6 oil. So I will drain this first and then fill with PAG-46. I should spin the wheel a few times to ensure the clutch is lubricated. Is this correct? Anything else about filling the compressor with oil?

Are you sure the new compressor came factory filled with ND6? I would be surprised if it did. I would expect ND8. Regardless, if you drain out whatever is in there now, fill and drain (flush) it a few times with PAG-46 only—no solvents— rotating the main-shaft by hand a few times between flushes. Then fill it for the last time to specs.

You can put all the oil into the new compressor if it will fit. If not, oil-balance the system by putting 1.5 ounces each in the evaporator and condenser, 1 ounce in the R/D, and the rest (3.5 ounces) in the compressor.

Rotate the compressor's main-shaft by hand several times (using a socket wrench, if necessary) just before you evacuate and charge the system to ensure that the compressor doesn't "slug."

murphtron wrote: ↑Mon Sep 26, 2022 3:08 pm What is the PAG-46 oil volume you have for my system? You had mentioned the Toyota document is different than what you have. Or should I stick with 100cc?

Forget the 100cc's mentioned in the TSB. That's not accurate for a "dry" fill, as mentioned earlier. The specs that I have for your truck are 27 ounces net weight of R-12 and 7.5 fluid ounces of Mineral Oil.

Of course, you'll be using PAG-46 oil in the same amount as above. As for the refrigerant, I would suggest starting with 22 ounces of R-134a (weighed-in properly, of course) and working your way up from there while monitoring the pressures and center vent temperatures. If the pressures start to rise above the normally expected range, along with the vent temperature, you have arrived at the "sweet spot," and you should stop charging at that point.

murphtron wrote: ↑Mon Sep 26, 2022 3:08 pm The receiver/dryer instructions say to add 20ml PAG-46 oil to the OUT side. Make sense?

The 20ml spec equals about 0.75 of an ounce. To make it easier to measure, I suggest putting in 1 ounce as mentioned above.

murphtron wrote: ↑Mon Sep 26, 2022 3:08 pm All of the new components seem to be under vacuum, and I've read the receiver/dryer should be installed last. Is there an order I should install the parts? As soon as I remove the seals from the eval and condenser, air will enter the system. So does it matter? I assume the receiver/dryer is installed last as it contains a desiccant and should remain sealed for as long as possible.

The fact that all the parts are under vacuum is a good sign that they are factory sealed and no contaminants have entered. You'll have to remove the seals as you connect them, of course. I would start with the sealed evaporator, then the sealed condenser, capped-off compressor, connect everything to the lines/hoses (removing the seals and caps at that point), and finally, install the R/D.

So yes, you are correct. Install the R/D last and as quickly as possible to minimize the entrance of air and moisture. A thorough evacuation for a couple of hours (or more) using a high-quality electric vacuum pump (not shop-air powered) will remove any air and moisture that might have found their way into the system while you were assembling it.

Any components being reused should be thoroughly flushed. The evaporator, condenser and hoses should all be flushed. There is really no reason to make new hoses as the myth about the R134a bleeding through the hoses was just that, a myth. Like the Loch Ness Monster.

We used 91 or 93% alcohol as a flush agent. It is flammable so you will have to be careful. However, it is environmentally safe and inexpensive. We had a pressurized vessel to use as a flush gun and it worked great. You can run the discharge line into a container and dispose of properly as well as inspect for a clear discharge.

Use plenty of compressed air to dry the inside of the components. Your system is old enough that you can flush the condenser too. Also, for the condenser, wash the external thoroughly so that you have good airflow when the system comes to life.