A/C - Sticking with R12 but looking for help

[DANTIP]

Originally Posted by WorkinLonghorn

Just a note. I have experience with commercial AC systems and some knowledge about Vehicle ACs and I wanted to point out that the correct way to leak-test a system is to use pressure, not vacuum. The shop I use to test systems uses 300 PSI of nitrogen.

If you use vacuum, you are using 14.7 PSI. and if there is a leak you are sucking air and moisture into the system which is always bad.

You can also use a Halogen leak detector ( around $30 on e-bay etc.) on a system pressurized with Freon. WL

x2! Nitrogen pressure test will help find small leaks that would lead to lost R12!! I like to spray a mixture of Prell shampoo and water on the connections. The mixture clings well and will bubble/foam nicely.

Good luck!

[gable74]

I had an A/C guy here at work take a look at my setup and he said he could see some green on the brass/copper washer in the sight glass which indicates contaminants in the system. He recommended I replace the Dryer, O-rings, evacuate and recharge the system. So it looks like that's the plan in the next week or so.

[gable74]

If I wanted to FLUSH the system. What is involved in doing that and can I do it at home or is there equipment required?

[F.A.A.benny]

just need compressed air. There are flushing solvents that are available at the local autoparts store

[gable74]

Got my new expansion valve today and its the type without the bulb on the end. It just has a copper coil. Do I just wrap those coils around the outlet pipe and clamp in place like I would the bulb? Then add the tacky tape?

Thanks,

[F.A.A.benny]

Originally Posted by gable74

Got my new expansion valve today and its the type without the bulb on the end. It just has a copper coil. Do I just wrap those coils around the outlet pipe and clamp in place like I would the bulb? Then add the tacky tape?

Thanks,

Yup, same way

[Jrainman]

Originally Posted by F.A.A.benny

just need compressed air. There are flushing solvents that are available at the local autoparts store

Do not use compressed air / you need to use Nitrogen to flush the system .

if you had compressor failure then you would need a cleaning agent that is used along with nitrogen to push it through the semi hermetic refrigeration system .

if your system just had a leak from a part or line failure then all you need to do is vacuum the system down to absolute vacuum ( 29 mercury) this is the way most pros will go before charging said system.

But the correct manual procedure when using R 12 will tell you when a leak is present is to use nitrogen then vacuum and then charge.

Any type of air in a refrigeration system is considered a NO NO . (contamination )

you can buy a cleaner in a aerosol can that is charged with nitrogen at any HVAC supply house . this product is used when you have compressor failure or if you are converting a refrigeration system from a CFC to a Non CFC as like going from R12 to 134a

If you noticed I have been calling it a refrigeration system Not ac and that is because the R12 AC system in your truck is really a refrigeration design.

you can also obtain Nitrogen at your local HVAC supply house.

[F.A.A.benny]

I am not a service tech and I don't work in the commercial/residential hvac industry. I restore/rebuild factory classic automotive a/c and heating parts. I used to work for a company called Classic Auto Air and that's where I learned a bulk of what I know. So my advice/opinions can be taken for whatever one feels its worth. If the OP is going to flush the system then it will probably be done with parts out of the truck( at least that's how I would do it). And that would meant that all these parts would already be exposed to air so its safe to say that it really isn't avoidable to keep air out of these parts. Even if he bought all new parts they would still be exposed when they go to get installed. That's why the system gets put in a vacuum for a sufficient amount of time. So flushing evaps and condensers with compressed air has never been a problem for me. Now for pressure checking to find leaks in these parts, I do use nitrogen. And as far as fushing agents go, CAA did not use any fancy hvac specific flushing chemicals. They used good old fashion brake cleaner

[Jrainman]

Originally Posted by F.A.A.benny

I am not a service tech and I don't work in the commercial/residential hvac industry. I restore/rebuild factory classic automotive a/c and heating parts. I used to work for a company called Classic Auto Air and that's where I learned a bulk of what I know. So my advice/opinions can be taken for whatever one feels its worth. If the OP is going to flush the system then it will probably be done with parts out of the truck( at least that's how I would do it). And that would meant that all these parts would already be exposed to air so its safe to say that it really isn't avoidable to keep air out of these parts. Even if he bought all new parts they would still be exposed when they go to get installed. That's why the system gets put in a vacuum for a sufficient amount of time. So flushing evaps and condensers with compressed air has never been a problem for me. Now for pressure checking to find leaks in these parts, I do use nitrogen. And as far as fushing agents go, CAA did not use any fancy hvac specific flushing chemicals. They used good old fashion brake cleaner

I don't see why the system would have to be broken down and removed unless a part has failed and needed removed to install a new part.

If the Op is looking to just flush the system there is no need to remove anything , flushing the system in tact just as you would your cooling system.

The more you expose the system to air the more chances you will have for A) failure of operation and or premature compressor failure.

Its not the air so much that is the problem, its the moisture that is present in all air.

this is the reason there is a filter dryer in the system with a sight glass and a eye that will change in color to let you know the condition of the Freon in the system,but it only can filtrate and dry so much

a lot of A/C and refrigeration parts are made and shipped pre charged with Nitrogen to keep the interior sterile

Nitrogen will keep the system sterile , any air left in the system will be compressed and leave moisture in the system.

Nothing fancy or expensive about the product used to flush a A/c system just has what you need in it to do the job right if you have compressor failure or switching over from r12 to 134a

the OP has done some reading on the subject and has concerns , I was just stating that the correct way will let the system remove the max amount of heat and insure the longest life of the system.

there are many ways to skin a cat and get results

[F.A.A.benny]

Very true in that more than one way to do things. Don't really wanna get into a debate so ill just let the op decide on whatever he wants to do.

[hdff]

Originally Posted by F.A.A.benny

I am not a service tech and I don't work in the commercial/residential hvac industry. I restore/rebuild factory classic automotive a/c and heating parts. I used to work for a company called Classic Auto Air and that's where I learned a bulk of what I know. So my advice/opinions can be taken for whatever one feels its worth. If the OP is going to flush the system then it will probably be done with parts out of the truck( at least that's how I would do it). And that would meant that all these parts would already be exposed to air so its safe to say that it really isn't avoidable to keep air out of these parts. Even if he bought all new parts they would still be exposed when they go to get installed. That's why the system gets put in a vacuum for a sufficient amount of time. So flushing evaps and condensers with compressed air has never been a problem for me. Now for pressure checking to find leaks in these parts, I do use nitrogen. And as far as fushing agents go, CAA did not use any fancy hvac specific flushing chemicals. They used good old fashion brake cleaner

I can vouch for F.A.A Benny's restoration work. It was 1st class!!!

[gable74]

Got the new dryer and expansion valve installed today. Also changed the O-rings on the lines that I opened as well as a couple other connections that were easily accessible. I did not change the O-rings on the compressor or the POA valve though. I put the vacuum pump on it and let it draw down for about 6hrs. I then closed the valves on the gauges and let it sit. It didnt budge off 30" as far as I could tell but im going to let it sit over night and check it in the morning. If its still on 30, I will try to charge it up. I dont have access to nitrogen so I guess im rolling the dice a little in hopes it wont leak.

On a side note, is there a trick to not letting air in the system when charging? I mean there is going to be a little air in the center hose right? I guess i could vent it out for a second to be sure the air is gone but it just seems like its impossible to be completely air free when you have to swap 3 or 4 cans out to charge the system up. Any tips or tricks to that?

[drfloyd]

All you can do is purge the line a bit at the guage. You probably don't have the original sticker on there that tells you the system charge but if you do you can charge it on the money. That's one advantage of starting with an evacuated system. I'm guessing it's probably a pound and a half maybe.

[Jrainman]

the hose (blue) that went from your low side port to your gauge (manifold) should still be in a vacuum , the hose (yellow) that went from your manifold (Center) that went to your vacuum pump ,will be disconnected then hooked up to your can of R12 ......

open valve to R12 loosen hose at manifold for a couple seconds (bleeding Line) then retighten line to manifold . this leave r12 to the gauge inlet and you are in a vacuum state on the other side of gauge. you are now Air free

[gable74]

Well, I think Im good but I plan on picking up a leak detector just to make sure because I don't want to waste a bunch of r12. Anyway here is how the gauge looked this morning when I got up. As you can see its still where it should be BUT.....and I may be just being paranoid but I think it may have moved the width of the needle between 11pm last night and 11am this morning lol.

I guess a bunch of things could make the needle move that small amount (if it really did), but I think I will try a can and check for leaks before charging completely.

[gable74]

I did not detect any leaks but I had a few minor hiccups while charging.

1. I found that the heater valve was bad, so I replaced that.

2. I put 12oz. cans in. The Low side reading was between 29 and 30 and the high side was fluctuating between 200 and 220 with ambient temps around 90* outside.

3. After 4 cans and feeling that the air from the vents was pretty cool, I still had bubbles in the sight glass that would show up in cycles every 30 seconds or so. For about a minute it would be clear, then a surge of bubbles would flow by, then clear again.

4. The vent temperatures felt pretty cool. I didn't have a thermometer to put in the vent but I would say it was upper 40's. I plan to get a thermometer later and test more accurately.

I still want to check the blend door to make sure its closing properly as well as pick up a manual shut off valve for the heater hose.

The outlets were sufficient enough to cool the cab in 85 degree temps but I want to be sure the system is functioning 100%. My concern is that I am at the upper limit of my high side pressure and adding more refrigerant would overcharge the system.

Thoughts?

Here is a video near the end of the charging process.

https://youtu.be/Aff3rSX8naM

[gable74]

I'm going to keep talking to myself until I get this where I want it....LOL

Everything I could find showed that I should have put in somewhere between 3.25lbs and 3.75lbs of r12. When I stopped at (4) 12oz. cans, that only gave me 3lbs. So I added another 9oz. yesterday afternoon. The High side pressure stayed at about 200 - 210psi and the low side about 30psi, so that was good. After charging, then letting the system settle over night it looks like just about (maybe all) of the bubbles are gone from the site glass. I guess there tends to be bubbles cycling through during the charging process? Anyway, now all I can see is fluid movement in the site glass which I assume is normal? Here is another video taken last night during charging. I will post another later of how the site glass looks now.

https://youtu.be/NOuGzl8nywU

[gable74]

Temps at the vents seem good. Outdoor ambient temps were about 82 degrees here today.

37 degrees at the passenger vent.
38 degrees at the center vent.
39 degrees at the driver vent.

Sound about right?