Ferrari 308 - A/C Recharge

You don't need to do anything other than attach a gauge set to the compressor which can be done - or, I should say, SHOULD be able to be done without doing anything other than opening the hood unless there have been modifications that placed the new 134-approved fittings in non-OEM location. Rather than a gauge set you could simply attach a hose and can of 134 to the fitting on the input side of the compressor but without gauges you are totally guessing at how much charge you are installing. Undercharge or overcharge will not cool properly and overcharge can lock up the compressor.

Is this a first charge after conversion or to replace lost refrigerant? If the latter, then obviously the system is leaking and it would be good to address that at some point.

 

So I have a 328 that has the same AC set up. I am done with my engine out and put everything back in, new expansion valve, new drier. Hooked up a gauge set, a container of R12, turned the system on but it won't take any charge.

1. Does the compressor have to be on for the system to take charge? My guess is yes.
2. Is there a safety switch that disables the system if there is no charge? If so, is that a catch 22?

 

No, the compressor does not have to be running to take a charge. In fact, as you noted, the compressor won't run until there is a minimum charge present. Actually, you can fully charge the system without ever turning on the compressor. The high/low side pressures are equal in a properly working system that has not been running for a few hours; they are not separate, closed systems. But the important thing is to know how much refrigerant (by weight) is a full charge. Once that amount is in the system, some minor tweaking can sometimes improve the cooling a bit.

 

Forgot...

Can't think why you can't charge the system; should be as simple as turning on the feed from the can/observing the gauge. What is the pressure reading of the static system right now? If you did not pull a vacuum the pressure should be zero. If you did pull a vacuum, it should be in that condition as you attempt to charge. You can get a rough idea of correct charge by observing the static pressure and comparing the pressure/temperature to a 134 chart showing correct pressure at ambient temp. But by weight is better.

 

mike996, thanks for helping us out. Could you kindly advise what "gauge set" is needed and what the R134a quantity is? (And is everything you need available at NAPA?) My 308 has its original York compressor (part R206R-20141), and it was converted for R134a with a new dryer, O-rings, schrader valve and 134a service port kit. FWIW, I was told this type of conversion requires a recharge every year, and that's what I got out of mine.

 

In theory it shouldn't need a recharge every year, HOWEVER, 134 has smaller molecules than R12 which is the reason the shift to 134 required barrier hose on production vehicles. So that might be the reason for a tech saying it needs recharging annually - because it's leaking through the hose wall (assuming they are the original R12-type hoses) We are about to leave the house for the day - I'll reply in greater length this eve after we are back.

 

By weight use 90% of the R12 spec weight for the 134. The factory R12 fill for my '89 328 per the manual is 1KG (34 OZ) But CHECK your car's owners manual to to be sure of the correct figure - it is in the owners manual where it shows capacities for the various fluids. Of course, unless you have an accurate scale you are pretty much guessing on that 90%. Most refrigerant cans are 12oz which makes it hard to guess at - 24 OZ is too little; 36 OZ is too much. . I have seen some16 oz cans which made it pretty easy - two of them would essentially be the correct charge by weight. If you can find 8OZ cans you could come up with 32 OZ as well. But with 12's what I would do is load two of them and then start adding the third while checking the operating pressure per a 134/ambient temp chart. Here's one: http://acprocold.com/faq/r-134a-system-pressure-chart/

You will need a set of gauges like this: https://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html The Harbor freight set isn't the best quality in the world but it's plenty good enough for occasional use.

Napa will have the refrigerant - they might have a gauge set in stock; they can certainly get one.

 

I know this will be not well received by all the pros on here, but the fact is if the ac system is not otherwise leaking or failing, you can recharge using a can of 134 from eg. Walmart
https://www.walmart.com/ip/A-C-Pro-Professional-Formula-Refrigerant-20-oz-Can/36158903

Use the integral low pressure side gage to fill within an acceptable range of error. Yes, it won't be perfect, but as noted the original non barrier hoses mean you will need to top up every couple of years anyways, so you will never have a precisely charged system for very long. Of course, the new barrier style hoses is the gold standard, but on a Ferrari they are long, have hard to find fittings and can be trouble to route and replace, so not surprising many use the old hoses if they are in otherwise decent condition. But they will leak over time, probably about 4oz over a two or three years would be a reasonable expectation. The can noted can dispense part of the can, it is not all or nothing, so you can use a bit without venting the rest to atmosphere, save the rest for a future top up. This chemical is not meant to be released into the atmosphere.

Using the professional type gages, including the Harbourfreight ones with the high pressure side gage is risky for the average handyman. I don't trust a $50 gage and hoses to handle 150-200psi, at the least wear goggles and such other precautions, you don't want this blowing up in your face. The high pressure side is generally not necessary to measure, wonky readings on high and low side are used to diagnose system issues. To charge or top up a known good system does not require high side measurement. Nice to do, but not essential for most systems.

If you simply charge to about 35psi to 40psi on the low side, this would suffice at most ambient temperatures where one is typically working. Some of the can gages have the readings, other have a green zone that captures the acceptable range, often with an ambient temp compensating dial.

Combined with the rough volume expectations noted in this thread, you can get close enough for practical purposes with a simple fill approach. When in doubt under fill. Overfilling is where the compressor damage can occur. Under-filling, unless severely so, does not seem to have much equipment downside, you will just get less cooling power.

If the system is empty, you should draw a vacuum with a special compressor, these go for $100 or so, so not big cost if you need to do this. You do want moisture out of the system. Should install a new drier if the system has been open for a length of time.

I know the pros do what they do for good reason, and doing things to the highest standard with good equipment is a proper practice. It is not easy to know if your system is otherwise in good condition. But for eg. a known top up requirement due to porous hoses, or to deal with lost charge from eg. replacement of o rings or fittings that were leaking with an otherwise good system, I just thought it worth adding to the discussion a practical option appropriate in specific instances.

 

FWIW, a "pro" shop's ham-handed work on my 328's AC is what caused me to decide that the only way to get good work done was to learn to work on auto ac myself. I really had no interest in learning that skill but it has been well worth it.

Totally agree that the system should be evacuated first and that if you are going to seriously do your own work, you need a vac pump. Because these 3x8 systems are marginal even when working perfectly, IMO, you really need to get the system working at its optimum capability. I twiddled the fill on my 328 over a couple of days with the gauges looking for optimum readings both high and low. Note that your high side pressure will drop (or did for me) by simply removing the piece of flex duct that connects the evaporator to the ac vents below the radio cut out. The ducts restrict flow slightly which then increases high side pressure because of the reduced air flow through the evaporator. The pressure difference was not large enough to be concerned about so I did not leave the hose disconnected but others have said that the cabin will actually be cooler if you do so..

With regard to refrigerant...

Have you considered one of the hydrocarbon refrigerants? They can cool in the systems in these cars slightly better than R12, which is considerably better than R134. Admittedly the difference between HC and R12 is so slight as to probably not be noticeable under operating conditions. The molecules of the HC refrigerants are even larger than R12 so leaking through the hose wall is even less likely than it was with R12. I charged my 328 (with the original 1989 A/C hoses) nearly 4 years ago with Duracool and it cools as well today as it did then with no maintenance or additional refrigerant needed.

I do not want to sound like I am trying to convince you to go that way but it is worth looking into and at least being aware of it. Hydrocarbon refrigerants are NOT currently approved in the US for vehicle air conditioning systems so shops will not likely install it or deal with it at all. So it's totally a DIY thing. FWIW, it IS approved in other parts of the world for vehicles and many folks believe it will eventually be "normal" for vehicles in the US. But it has not yet been tested/approved in the US for that use. Some cynical people believe that the reason it is not certified is because the makers of standard refrigerants don't want it to be certified...

 

The HC ones are either propane or isobutane, and are by their nature flammable. They do work very well. I suppose would be like the risk of eg. a taxi running on propane, or less in that the total amount in an auto ac system would be pretty small. But, in the end, the flammability is what prevents the widespread adoption in the western world. Having seen propane rail tankers explode in my youth during the Mississauga train derailment (was just down the road from the rail crossing when it blew), let's just say I have a fear of propane to this day!

The future may well end up with HC blends that reduce the flammability. Too bad they don't redesign the whole systems and go with carbon dioxide.

 

Here is an old link from a fellow who repaired his 308 ac and charged with the HC refrigerant. http://ferrari.cdyn.com/carl_rose_docs/Ferrari%20328%20AC%20Recharge.pdf

 

There are two errors in that otherwise excellent post. It does NOT take 5 cans of Duracool for a fill. Five cans is more than double the necessary amount. 2 + a bit from a third can is the correct fill for an OEM 3x8 system. Also, pulling a vacuum of -25HG is insufficient to draw all the moisture from the system; it needs to be at least -29.5" and held for 30 minutes to do the job.

 

i just want to throw this out there... a good local shop did a proper r134 recharge in my 308 this season for about $60 total. Took less than an hour.

So consider that approach before you start buying a few crap tools from Harbor Freight and cans of refrigerant.

 

I agree that if all you need is a recharge of 134, any ac shop SHOULD be able to do that with no problem. But I would take it to a shop that regularly does AC work, NOT an exotic car specialist shop. The fact that the exotic car shop has a modern AC service machine with all the bells and whistles does not mean they know what to do with it.

My personal experience with such a shop (well-know Ferrari and other exotic car shop in MD) was that they overcharged my 328 with 134 to the point where the compressor locked up and they couldn't figure out why that happened. The tech said he figured he was putting in more than was really necessary but he "wanted to make sure there was plenty of refrigerant in there!!" He then evacuated it until the compressor would turn and called it good. The AC sucked. The shop before them (Las Vegas) charged it OK but it blew out later that same day via an O-ring fitting that they had improperly installed. They re-did it a day later at no cost but the AC quit two days later during my trip across country from Vegas to MD. I discovered that the same O-ring had been cut during assembly and was seeping. These events are what made me into an AC tech.

Remember, NOBODY is going to worry as much about your car as you are! Admittedly, that's to be expected. I spent a couple of days futzing with my 328's AC charge to get the OEM system to function as well as it possibly could, but a shop can't make any money doing that. And, to be honest, most of the time it isn't necessary. Most modern car AC systems (and heck, all US cars since the '70s) have ac systems with sufficient capacity to cool even if the systems are not in optimum condition.

FWIW, IMO Harbor Freight tools are fine for what they are - inexpensive tools that do the job for occasional repair work. They are not suitable for heavy duty, daily use.. That's why Snap-On is still around! To work on my Ferrari's AC once in a while - last time was 3 years ago - the harbor freight gauge set fine (though it's not the brand I have). If I was doing it daily I'd buy the Snap-On.

 

I should mention I took my car to 20+ yr running shop who's main business is auto AC repair. It's family owned, and I wondered if some of the "employees" were other family or a girlfriend that hangs out there all day. The cash box was one of those things you see at the church yardsale, and the receipt was hand-written. Spotless, it wasn't. No cappuccino machine in the waiting area, and the sofa was pretty dated (yet clean, and oddly comfortable.)

The tech was great. After we got through all the "Whoa, Ferrari" stuff, he pulled the AC equipment cart to the parking lot. He took great care in snaking the hoses into that cramped engine bay without scratching anything. When it came to lbs/capacity, he excused himself for a bit to do some google research instead of just "let's fill 'er til she pops cold air." I managed to download the WSM manual on my phone, and he did a good r12-134 weight calculation to make sure it was correct. I think he erred on the side of caution, actually.

So as Mike mentioned, if you really just need a recharge, find a nice dedicated shop. DIY is great, and I love doing it, but AC is one of those really specialized things that I prefer to leave to a trained, licensed tech with good experience and the right tools.

And please don't fill your AC with some explosive propane derivative. Use an approved refrigerant. They do work, if the rest of your system does.

 

"When it came to lbs/capacity, he excused himself for a bit to do some google research instead of just "let's fill 'er til she pops cold air."

THIS is IMO, the mark of a really good Tech - a guy/gal that will go look up something to be sure rather that guess or figure "X" is close enough. There is nothing embarrassing about by grabbing a service manual (or whatever) and looking up the info though some "mechs" act like it is.

 

Isn’t the compressor supposed to be running when you charge it?
I’m talking if you are doing it yourself with the stuff from auto parts store.
That’s what all of the things I’ve seen have been saying.....but that doesn’t mean it’s right.
I’ve always had good success with that in past but haven’t ever tried it on a Ferrari.

 

You can add refrigerant to the system without the compressor running because the high/low systems are connected through the expansion valve but, yes, it is charged with the engine running/compressor ON. Note that if there is insufficient pressure in the system -as there will be in your situation - the low pressure switch will keep the compressor "off." So, initially, even though you have turned the AC "on," the compressor will not engage until you have added enough refrigerant to close the switch/turn on the compressor. From that point you just continue adding refrigerant until you have added the correct amount by weight. Monitor the gauges as you are doing that to see that pressures on the high and low side fall in the range appropriate to the ambient air temp. If they don't, there is an issue with some mechanical aspect of the system - compressor problem, expansion valve, etc.

As has been stated in other posts, excess refrigerant is worse than insufficient refrigerant as far as the system/components are concerned.

 

Since no one answered you... some of the R12 old style valves have an internal shutoff. There are two caps, one to attach the lines, one to expose a valve you can turn with an allen key. Hook up the service gauges and then open the valves with an allen key. The newer R134 lines have a shutoff valve on the quick connector where the older style R12 just gets a hose. You close the same valves before you remove the service lines. You will lose freon from the lines when you disconnect but in the old days that was okay to let it trash the ozone layer

1) The system does not have to be on... but you may need to run the compressor to get the full charge into the system.To get the compressor to kick on you will need some refrigerant in the system to close the low pressure switch

2) There are usually both a lower pressure switch and a high pressure switch. The low pressure switch opens when the suction side is less than about 15-20 psi to protect the compressor from running dry. The oil is mixed with the refrigerant in the system. If the freon level is low, there is less oil and freon and the compressor will get less lube when it is trying to run harder... that would be bad. There is another switch on the high pressure side to cycle the compressor clutch off when the high side pressures get high... 350 psi or so. It will cycle on and off to maintain pressure as it needs to, Not sure what the Ferrari spec for the switch pressures are but its something like that.

My 328 has a R12 capacity of 1kg or 2.2lbs of refrigerant. For R134 that would be 2.0 lbs

 

Just to add to this,sometimes the gauge hoses don't depress the shraeder valve when they are screwed on so that could also be a reason why the system isn't taking charge..
Just confirm that it is depressing the valve stem allowing for the refrigerant to flow.

 

I watched they ac shop evac my r12 system and there is no allen key. ... I have to get back to it again to check.

 

That's correct, there is no allen key valve on the original R12 system,just the schraeder valve.

 

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