A/C schrader valve size?

you say you think they are leaking. How do you know for sure? Did you do the simple soap bubble test? If not, thats the first thing you gotta do. Even with a low charge, you should get bubbles.

many times, you can tighten them down just a tad more. Then test again with soap. let us know, Rick.

 

Hi Rick,

The valve cores for our 308/328s are a very common, 'standard' size. Try Napa auto parts, p/n 209578. Another brand is FJC (p/n 2672). Most auto parts places should have them, just don't use the ones for tires as their seals aren't meant for refrigerants. You can also get these cheap online. HVAC Tools, HVACR Tools, Refrigeration Tools and Sheet Metal Tools has a 6-pack (with nice teflon seals), (p/n C&D Valve CD4460-6). Put a drop of refrigerant oil on them (or Nylog if you have it), tighten to 'just snug', and you're good to go.

There are also two "Rotoloc" nylon sealing rings, one between each of the fittings and compressor that could leak. Napa has these for about a buck each (p/n 207165). Too cheap not to replace during a service.

The original compressor (Aspira/York type) was used in thousands of 1960's-1980 Fords and is still used in large trucks, so unless you have a different (e.g., Sanden) compressor these should fit the original fittings just fine.

Good luck!

Ciao,
Vincent

P.S. If you don't already have one, get a valve core removal tool. They're really cheap and, unlike needle-nose pliers, they won't nick the core openings.

 

what pressures were you looking for on the gauges when refilling the system?

 

Youre doing much good work/care, but note- unless those guages are of extremely high quality, that 2 " Hg over an houur + could be due to guage leakage, and not the system. Just beware......

good luck, Man.

 

Thats a LOT of vacuum (leakage) to lose in an hour and a half. So you need to find the leak(s).

As far as charging...the accurate way to charge is by weight so you have to totally evacuate the system and then install the proper weight of refrigerant. That weight is listed in the owners manual but, of course, you have to adjust the weight for the refrigerant used vs the original R12. The gauges will not help you at all for that particular purpose. OK...they are not USELESS for that but they will not tell you much because system pressure varies based on temperature. So a correct charge that produces X psi on a 70 degree day will produce considerably higher pressure on a 90 degree day. Static pressure will tell you if there is enough refrigerant to activate the low pressure switch so the compressor will run but it won't tell you if there is too little or too much refrigerant for proper cooling.

How much vacuum was your modified compressor pulling? For best results, it needs to be more than 29.95" and it should hold that for at least an hour (though most shops will not actually hold it that long) and it needs to be pulled with a proper pump for that job. The fresh refrigerant oil in a vacuum pump (as opposed to the old oil in your system) is an important part of filtering and ensuring the removal of all moisture. The oil in the vac pump is not JUST there to lubricate the pump. Vac pump oil should be changed quite regularly for that reason.

Some would point out that Duracool (propane) is less subject to problems with moisture and therefore pulling/holding a high vacuum to purge moisture is less important than it is with R12/134. This is true but the vacuum is still important to ensure removal of all the old refrigerant and for leak-checking. I wouldn't argue with someone who said you don't need as much but neither would I change what I have been doing and use reduced vacuum.

 

Well, your two cans initially are about right and should have cooled reasonably well...I can't explain that.

When I first switched to duracoo l(plus new drier and exp valve) I had exactly the same problem - I overcharged it and the system didn't cool well at all. After figuring out the problem, I dumped the charge and re did the entire process (vacuum/recharge), this time with 2 cans of Duracool. Cooling was dramatically better. Then I slowly bled off some of the charge, watching the ac vent temperature with the ac on max and the engine at 2000RPM. It dropped slightly as I bled off, showing that the 2 cans had overcharged it. When it stopped dropping, I quit bleeding off Duracool. On a 90 degree day at 2000 RPM I was showing approx 170/35 PSI. The system worked pretty darned well for a 3x8 Ferrari for several years though this year I developed a system leak that I have yet to chase down. I suspect the oem original hoses have permeated.

There is as much art as science involved in this stuff..

Did you install a new expansion valve and drier? They should be considered a normal part of the recharge job though your static/high/low gauge pressure indicates the exp valve is working.

One thing I did (there are posts of it here from a few years ago) that helped was to I remove the louvered panel from the rear of the condenser. I also straightened some bent fins and made sure the entire condenser was clean. I replaced the louvered panel with some heavy gauge but large-opening screen wire. This made a noticeable improvement in cooling, especially when moving slowly. There is very little airflow through the condenser at low speed with the fan running and the panel in place compared to the flow with the panel removed.

I will not say that I ever got the ac to be better than what I'd call "fair," but it was good enough to be reasonably comfortable in the car at cruise speed in temps up to the low 90's. That being said, I like the cockpit to be in the low 70's and on a day in the 90's with the sun full on the dash, the ac could not keep it down to that level. Around 80 was as good as it could do in those conditions. Vent temps were low. The problem was that the evaporator was just pushing enough cold air into the cabin. If the sun was not full on the dash, regardless of outside temp, the cockpit was comfortable to me.

 

Hi Rick,

My replacement drier did not have a sight glass but everything I have been told and read re this is that a sight glass is only useful with R12 - that only R12 has a correct charge when the glass just clears of bubbles. Anything else - 134/propane derivatives, etc, will have bubbles at the glass with a correct charge and therefore sight glasses are no longer useful. That's why many modern car ac systems do not have sight glasses at all and modern automated ac charging systems function totally by weight. Years ago, R12 systems were recharged by simply adding R12 until the sight glass cleared. Life was simpler then!

The comment that your Duracool guy said - charge until the glass is clear - is the first time I have ever heard such a recommendation for charging with anything other than R12. When I contacted Duracool after I overcharged, the guy I talked to said to charge it strictly by weight (converting from the R12 weight to the appropriate Duracool weight.

I have no idea why Duracool would make such a recommendation; clearly, it doesn't work that way in real life. I overcharged mine with DC the first time by looking for a pressure reading as opposed to weight. Duracool ends up with slightly lower pressure readings than R12 and FAR lower than 134 with the system cooling at best efficiency.

Good Luck! I'll be away from where my 328 is located for several months so I won't be able to do any work on my leakage issue until September...

 

" A/C systems are one of the few things on a car I've never worked on until now."

I can identify with that! Other than adding some R12 in the "old days" I knew nothing about ac and didn't WANT to know anything about it. But two trips to shops that were allegedly experts, one of them a Ferrari specialist, where they succeeded twice in making the ac work WORSE, convinced me I needed to learn to do it. So my 328 became my "learning experience." Now I have all sorts of "friends" who want me to work on their ac!

"Would an infrared thermometer measuring the metal pipe temperature near the drier work?"
Maybe, but I don't know if that would give you an accurate measurement of what you need to measure. The standard method still seems to be a thermometer in the center vent.

Make sure when you are testing that the windows are fully open and the settings are for max cool. If you don't open the windows, the interior could cool down enough to cause the compressor to cycle off, thus raising the vent temps until it cycles back on, lowering them again. I had both DOORS wide open to ensure there was no way for the interior to cool and shut off the compressor!

 

Our 308s use a York similar to that on the Porsche 911, to answer one of your simpler questions...

 

The only way to accurately fill a AC system is using an accurate temperature probe and a pressure gauge to measure the temperature and pressure of the superheated refrigerant entering the compressor, the temperature of the air at the condenser and evaporator and then matching the numbers to a chart for the refrigerant and determining the degrees of superheat of the vapor going into the compressor.

The original design of the system took a lot of stuff into account and they determine where to put the sight glass so that on a normal temp day the fluid going going past the glass is a subcooled liquid. Changing refrigerant and/or the system layout or volume throws that location off and you cant use it to determine charge levels.

Look up superheat and subcool on the internet to find the right charts and how a system operates. For propane or Duracool you need to find a chart for R-290, you could use R22 chart though as the numbers are pretty close.

With a low side pressure gauge and a temp probe clamped to the inlet line to the pump and a thermometer for air readings you can determine charge levels and get the system efficiency as its optimum levels.

Using sight glasses or just a gauge set without superheat charts and temps... is just a guess. For a standard automotive system, the guesses can be pretty good... but its still only a guesstimate. When you swap refrigerants or change component sizes or capacities... the accuracy goes down fast.

Learn about subcooled liquids and superheated vapor and you too can get your AC running as good as it can with the parts ya got.