2 things : Off-Idle and A/C Pressure Check

[Mark H.]

Three questions :

1 - just rebuilt my 65 SB and it's Holley 4150. Running fine except for just after idle (clutch out @ around 1200 rpm) it goes lean on me - surges on/off hard until I gas it onto the mains (idles and runs on main jets fine). Very much like a plugged pilot jet on my motorcycle. Carb was cleaned thouroughly after full disassembly. Float level is right; stock jets. Thoughts ?
2 - Just had my A/C A6 compressor and dryer rebuilt. Before the compressor lost a seal the sytem worked fine and a mechanic told me that it was leak tight. A/C guys are now telling me that they don't want to just fill it up with oil and R134 because "the 1965 lines are not made for R134" and "when empty, the lines get all corroded and ....". Any problem with running R134 in a stock system (compressor is OK with R134) ? Lines were fine, but they did sit in an refridgerant-free, non-pressurized state for months with the compressor off. Could this have ruined the hoses and justify new hoses ? I'm tempted to fill the system and try it.
3 - If I were to chose to do a A/C system leak check I'm told they only pull about a 30 psia vacuum, and that this is not enough since the compressor puts out a lot more than this and so the check won't show all problems (then why the heck would anyone do a check like this?). Why can't I do a positive pressure of a higher pressure and do a similar leak-down test ? What pressure should be used (or not exceeded) ? Again, since it was leak tight before removing the compressor, I'm tempted to find someone who will just fill the thing (anyone know of a good A/C guy in So Cal ?)

Thanks for reading all this,

Mark

[Terry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

The hoses used in modern cars with R134a are called "barrier hose." There is a plastic liner in the hose that acts as a barrier to the refrigerant. Can you run it without "barrier hose" Sure. Will the hose, especially 40-year old hose leak? Sure

If the system was open to the air, atmospheric moisture (humidity) can combine with the HCFC in the refrigerant remaining in the low spots of the system and form hydrofluoric (or maybe it is hydrochloric, I forget now and chemistry was NEVER one of my strengths) acid. Whatever kind of acid forms will eat holes in the aluminum parts of the system. I think that is what they meant -- and yes it can and does happen.

Don't be discouraged though. You can get your system working again.

BTW: I don't know of any HVAC service machine that draws much better than 30 in Hg. The ones I have worked with draw about 27 inches, and we were taught that is good enough. When I work on my own cars I leave the vacuum pump hooked up overnight, and hang a light bulb by the accumulator/dryer to get the moisture out of the desiccant. But time in the bay means nothing to me -- to a busy shop it is hundreds and maybe thousands of dollars -- so they want to do slap bang and out the door.

You just need to find some better options.

[Mark H.]

Re: 2 things : Off-Idle and A/C Pressure Check

Yikes ! Thanks Jim. That answers that question. I didn't know that R134 was such a different animal than R12. I'll order Paragon's 8934K and 8935K hose kits (let me know if I need something else - I assume that the STV is OK as is).

Thanks,
Mark

[Terry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

I am not sure what those hoses and fittings look like, but I suggest you decide if judging is in your future for the car. If function is more important than form, they may be fine -- but I suggest you wait for some others to chime in with their personal experiences before you order anything.

[Mark H.]

Re: 2 things : Off-Idle and A/C Pressure Check

Terry,

My car is a driver but in very original condition, other than my just-done motor rebuild. So function is the important part but, yes, I also want it to be as original as possible since everything else is. Let me know if you know of a better source than Paragon/ZIP/Long Island/.. to get both of these. I may send out another thread titled "hoses" or something to get some replys.

Thanks, Mark

[Terry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

I have no knowledge of the configuration of hoses from various vendors. I do know when we judge the AC; newer hoses have crimps with a different configuration (by law) than the original hoses. This results in a minor deduction. Replacement POA valves have a different configuration than original -- a few points there. Some of the service replacement hose/manifold assemblies have a different configuration than original and result in a couple of point deduction as well.

It might be best to start a new thread about AC. I am sure there are many here who can offer first-hand advice -- you just need to attract them to the thread.

[John H.]

Re: 2 things : Off-Idle and A/C Pressure Check

1 - just rebuilt my 65 SB and it's Holley 4150. Running fine except for just after idle (clutch out @ around 1200 rpm) it goes lean on me - surges on/off hard until I gas it onto the mains (idles and runs on main jets fine). Very much like a plugged pilot jet on my motorcycle. Carb was cleaned thouroughly after full disassembly. Float level is right; stock jets. Thoughts ? Mark

Mark -

Sounds like an accelerator pump issue - the pump shot covers the temporary lean condition between idle and main metering. Check the pump arm adjustment - the .015" clearance referenced in the Overhaul Manual MUST be done with the linkage HELD WIDE OPEN and the short pump lever pushed down in order to get an instantaneous pump shot. Takes three hands or two plus one very stout rubber band.

[Larry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

Mark:

A few questions/comments regarding your AC problem:

1. Who rebuilt your A-6 compressor and drier? What drier dessicant did they use?
2. How long was your AC system open during this time? Did you plug or cap off the openings?
3. There are two companies that advertise that they have duplicationg service for air conditioning hoses. Classic Auto Air (Florida and Texas) and Old Air Products (Texas). You can contact them regarding correct reproduction hoses. Both have websites that include phone numbers. I have not personally seen their reproduction hoses, so I cannot comment on their product. But it should be worth a call. You can then compare against Paragon and LICS products regarding cost and correct configuration.
4. If your old system last contained Freon-12, you cannot charge 134-A without cleaning and flushing the system to remove the old oil. It MAY also be necessary to revise the STV/POA setting for maximum benefit.
5. Regarding the vacuum test, it is mandatory that you pull a high vacuum on the system to remove air and moisture. You try for 29.92 inches of mercury (Hg) vacuum....full vacuum. Once you achieve the vacuum, you typically valve the system in for a few hours and see if it holds, or if you have an air leak into the system. The vacuum test therefore accomplishes both an air/moisture removal function and a leak check. You COULD also leak check all the fittings etc. with dry nitrogen pressure and soap solution, but this is much more difficult to do correctly due to the number and location of the fittings, etc.

Answer a few of the questions above, and then let's see where we need to go.

Larry

[Mark H.]

Re: 2 things : Off-Idle and A/C Pressure Check

Thanks John. I did have a heck of a time convincing myself I had that adjustment right. I held the linkage wide open but was confused by "holding the pump lever down all the way" - how hard should I push on that lever ? It doesn't have a hard stop feeling to it but rather goes and goes and goes to where I'm guessing I will reck the valve.

The arm seems wierd in that I can slide the arm off of the PV radially with a little pressure and make it actually come of the valve (regardless of the 0.015" gap). I would think that there would be less slop in the mechanical linkage than to allow that.

[Mark H.]

Re: 2 things : Off-Idle and A/C Pressure Check

Larry, Answers to your questions :

1 & 3 : A6 was rebuilt by Classic Auto Air, who has told me that it is ready to go with R134.
2 : System was open for months. I did a poor job of plugging the hose feeding the compressor and the line feeding the dryer with electrical tape (geez...)
4 : System did have R12 in it . I would plan on having an A/C house flush the system well. I wonder if my local A/C shop will know how to adjust the STV setting .... Classic air did mention that 20% less R134 goes in than R12
5 : I have a vacuum guage to verify the 29 in Hg, but how do I pull a vacuum (can I buy a hand pump ?) ? Given that it must sit for a few hours, I'd love to do this check myself and not pay the A/C guys.

Thanks a lot,

Mark

[Larry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

Mark:

My recommendation would be for you to keep using R-12 and not to convert to 134A. I know the $$$ price difference in the refrigerants, but I think that you will be happier staying with R-12 in the long run. However, I will provide you both recommendations.

For R-12: I would remove the expansion valve and the STV valve, (compressor and drier not yet installed), and then using dry air gently blow out the old residual oil from the condenser, evaporator, and hoses. Keep air pressure low, say below 30 psig, if possible. Since your system was open for many months, the old oil is probably contaminated with moisture and is acidic. Then reinstall the expansion valve and the STV valve using new o-rings. Install the compressor using new o-rings and the required amount of R-12 compatible 500 SUS mineral oil (available NAPA, etc). Do NOT install the new accumulator drier, but bring it with you to the AC shop with the car. Let them pull a vacuum on the system, do the initial leak checks, install the new drier, do a final evacuation and vacuum/leak check, and then fill the system with R-12. (Requires about 3 to 3-1/2 pounds of R-12 total charge). Then have them start the car and check operation and performance of the air conditioning.

The drier contains a desiccant that will quickly absorb moisture from the air, and must not be installed until just prior to final evacuation and charging R-12. A special refrigeration vacuum pump is required to pull a deep vacuum on the system and remove air and moisture. You can't do a good job on your AC system without one.

Before starting on converting to 134A, I will go ahead and post this. My computer has a habit of acting up and losing my current message during typing, and I won't retype this again.

Second part later. Larry

[Larry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

Mark:

For 134A: Your compressor and accumulator/drier may be ready for 134A, but the rest of your system is not. 134A requires a special oil that is NOT COMPATIBLE with your old refrigerant oil, it takes different material o-rings, the old hoses may permeate through and lose some 134A during operation (Terry McManmon post), and ideally the evaporator should run a few psi lower pressure. I know that 1967 and up POA valves can be removed and bench set to achieve this difference, but I am not certain what can be done with the older STV. I checked back thorough my files, and could not find anything about the STV. I recommend that if you proceed with 134A, you call CLASSIC AUTO AIR and ask them what (if anything) can be done. You may just have to live with slightly poorer performance. For a POA valve (example) you would set the backpressure from OEM setting of 29-30 psia to 26.5 -27 psia when changing from R-12 to 134A refrigerant.

I would then recommend removing the expansion valve and STV valve, blow out any residual R-12 oil, then thoroughly flush the condenser, evaporator, and lines with a special refrigeration conversion flush (available NAPA, etc), then blow through the system with dry air to remove the flushing material and dry the system. Then bench clean the expansion valve and inlet screen, and the STV valve of old oil as best you can. Install new 134A compatible (green color) o-rings everywhere and button the system up. Purchase the correct 134A compatible oil and add the oil to the compressor. Then install the compressor with new o-rings. Take the car and the new accumulator/drier to the AC shop as I described for R-12 and have them do the same leak checks, system evacuation, etc. and install the new drier. As you pointed out earlier, you (they) will charge about 20 percent less 134A to the system (compared to R-12) and check air conditioning performance.

By law, the AC shop must replace the R-12 suction and discharge connections with 134A type connections and add a 134A charge sticker to your system. You might be able to work around this ($$$), but just be prepared for this possibility. It is current law.

Many people convert to 134A and are happy. Some are not. If later, you are one of the unhappy ones, you get to reverse the steps above to change back to R-12. Your call.

Hope this helps. Larry

[Mark H.]

Re: 2 things : Off-Idle and A/C Pressure Check

Thanks for the info Larrry. I appreciate your input. I like the idea of just replacing with R12 - more money but easier to just have to remove the moisture as opposed to oil and air. I've spoken with some people that feel leaving my non-leaking hoses, condensor, evaporator alone and just dry them out. Any last thoughts with the "dry and put in R12 back in" plan ?

Thanks again for the help

Mark

[Larry M.]

Re: 2 things : Off-Idle and A/C Pressure Check

Mark:

I think you will be happy with your decision to stay with R-12.

If you do not want to disassemble any more of your system to try and remove the old oil (which will likely contain some moisture and acid), then I recommend that you have the AC shop pull a DEEP vacuum on your system and hold it for a least an hour to remove as much moisture as possible.

HVAC books I have indicate that water/moisture will boil off at around 1500 MICRONS absolute pressure; and that you should try to hold 500-700 MICRONS pressure (29.90 in HG vacuum) for an hour to obtain a completely dry system. A special micron pressure gage is needed to measure these values, but a good HVAC shop will have one.

Larry

[Page C.]

Re: 2 things : Off-Idle and A/C Pressure Check

Hi Mark,
Larry has provided some great advice. I also think you will be happier with the R12. The purpose of the vacumn pump is to remove moisture from the system. The amount of moisture should not exceed 10 p.p.m.(parts per million) Moisture in greater concentration of 20 p.p.m will cause serious damage. One drop of water in an air condition system having a capacity of three pounds amounts to 40 p.p.m. or twice the amount that is can tolerate. This info is from one of my old auto air books by Boyce H. Dwiggins.
Page Campbell