348 A/C 30A Fuse

Fully charged system will provide what is better described as a "blast" of refrigerant from service valves. A clue to leak in evaporator core is to inject dye, run car, then shine blacklight on puddle of water from evaporator drain hose. Another spot to check (assuming leakage) is condensor core -usually in front of radiator, susceptible to road rock damage.

Carl

 

Congratulations Daniel! You're now well on your way to being a Ferrari mechanic. You've confirmed major system components functioning and no huge leaks. "Converted" systems (R-12 to R-134a) may or may not cool as efficiently as original, and you currently have air in the system. What you need to do now is 1.) confirm system integrity 2.) replace reciever/dryer, and 3.) recharge system. Fortunately you're using R-134, so still readily available and relatively inexpensive.

Before you start on the above, you'll need to invest in 1.) quality set of guages/hoses for 134a, 2.) leak detector kit (I prefer fluorescent dye), and 3.) rent/buy vacuum pump. Gauge/hose set will run about $75-100, leak kit about another $70 (there are cheaper ones, but the design on the one I purchased makes it worth extra $20), and vacuum pumps new are about $250/used $100 (found mine in pawn shop) or often can rent for $20/day. Even if you buy all of this new, you'll still spend less than shop charges. And you can work on your other cars. Have bill for previous service on my car - $800-odd for expansion valve replacement and recharge.

Also *highly* reccomend the Haynes Automotive AC manual (ISBN #1850104808) and looking over my 328 AC article on the other website. AC systems are fundamentally similar with assorted bells/whistles per car.

Now the 35lbs steady pressure...reading only lo-side pressures you're only getting half the data. I have personally noticed that adding subsequent cans does not always result in commensurate bump in hi-side pressures. Not a physicist, but suspect involves timing of expansion valve opening and change of state from liquid to gas returning to compressor.

My personal procedure in this case would be to add dye, run car, and inspect thoroughly for leak. If none found, evacuate the system and see if vaccum holds. If not, you have a leak somewhere. If so, replace dryer, re-evacuate, and recharge.

Best of luck here - you're getting there.

Carl

 

I just got done reading this thread. Fantastic information. Currently I have no a/c at all in my car. The a/c never worked since I got the car. During the engine out major, I completely removed the compressor as it was not working. Later on down the road I do plan on diving into the a/c system, and all this info will be of great help when the time comes. Again, great work and help guys.

 

Daniel,

Another thing to check is the air recirculation flap. Make sure it works when the button is depressed on the A/C panel. I have seen quite a few cars where the drive to the flap is broken.

Here's a link to when I made a new part for it last year.

http://www.ferrarichat.com/discus/messages/256120/223545.html

Paul

 

You should have the recirc flap. I don't know where it is on my car, but when I select recirc on the control panel I can hear the flap engage and the air speed slightly increases.

 

Daniel, if the recirc flap doesn't work you'll never get the cold air you are looking for. You need to run the a/c on recirc esp when it is hot out.

 

A side thing to check is that the fan at the AC condensor is coming on and running well (since this is how the "heat" ultimately gets out of the system) -- when stationary with the AC running, you should feel a fairly strong hot air stream exiting the front wheel well where the AC condensor is located. I had a weak brush spring in my TR's AC condensor fan motor so it was running very slowly. Not saying that that's your problem, but it's just another area to check/confirm.

 

Daniel

I am a bit dismayed by your continuing problems. I was pretty certain your problem was entirely low refrigerent.

As to your recirculate door. On an optimally operating system, choosing recirc. over fresh air will reduce the output air temp by approx. 10 degrees. The recirc. setting helps the system maintain cabin temp more easily because it doesn't have to continually remove the heat and moisture from the outside air. Recirculate position does not reduce the ultimate temp of your evaporator assembly. The evaporator temperature is governed by the ability of your expansion valve to convert high pressure liquid refrigerent into a lower pressure gas. The gas is passed through the evaporator where the warmer air passing over the fins in the evaporator, condenses the gas back to a liquid. Thereby, passing the heat in the cabin into the low pressure refrigerent, which is passed back outside via the compressor and condensor. The most efficient use of your recirculate function is to use fresh when first starting your car, as the air inside on your cabin is most like 50-80 degrees hotter than the air outside of your car. Once the cabin is cooling off to temp erature closer to the outside air, switch over to recirculate. The system will operate at a higher efficiency level due to the reduced work load.

A telling point for me is that your low side pressure is going up. It sounds like you may have overcharged the system. If there is too much refrigerent in the system, the expansion valve becomes flooded and there is no room for the expansion of the liquid refrigerent into a gas at the back side of the expansion valve and into the evaporator.

You really need to see what the high side pressure is at 3000rpm. Even if you have bubbles in the sight glass you can still be overcharged due to the turbulence created in the dryer assembly. If you had way overcharged your system, your high pressure switch should shut down the sysem (ie. the compressor) to prevent compressor damage. It is possible that is what is happening when you drive the car. Once the high side pressure goes over the limit of the switch, the system disconnects the compressor and the a/c begins to warm up. As the pressure drops due to the compressor not turning, the a/c resets and the compressor begins to turn, causing the cycle to repeat. Your air would get colder at stops as the compressor is staying engaged longer, since it can't make as much pressure at idle as it can at 3000rpm, thereby cooling better, since it is running longer.

There is no need to fuss with the flaps and such in the evaporator case until you are certain the refrigerent system is functioning properly. Air in the sytem can also cause these kind of problems due to air's properties under pressure as it passes through the expansion valve. It can really upset the internals of the expansion valve causing it too vibrate the seat open and closed very rapidly.

Also, as 91TR mentioned, double check your condensor fan motor. However, if the condensor fan is faulty, the symptoms are magnified at idle. When you are moving down the road, the condensor is receiving forced air just due to your moving. At idle, your condensor fan creates the air flow to cool the condensor. So, your cooling should decrease dramatically at idle if your condensor fan is not functioing at all. Now, if the condensor fan is turning too slowly, there can be issues at speed due to the slow moving fan actually hindering the road forced air flow. This is not very common however.

I still feel very stongly, you have a refigerent flow problem. Either you are overcharged, or the refrigerent is not moving correctly. The only way to be sure is to know what your high side pressure readings are at idle and at 3000rpm.

I wish I had a repair manual handy, as it would give the exact spec. for refrigerent capacity. However, if you can get your pressures in the range of 30-40 low side, and 200-220 high side, you will be very close to right. You will at least be close enough to fully diagnose the system properly. Make sure when you re-evacuate the system, (which I think you need to do), run a vacume pump for a minimum of 30 minutes. Moisture and air in the system can screw up all of your readings and play havoc with the expansion valve and compressor.

Let me know what you find.

 

Guys - I have a question related to the use of R12 & R134a.


I am led to believe, maybe wrongly, that higher pressures are needed in the a/c system if it is charged with R134a as opposed to R12.

Therefore, all o-rings in the system need to be replaced.

Is this true ?

Is a 348 system designed to run on R134a and the resultant higher pressures. ?

Thanks

John

 

John

R-134 systems run at a slightly higher pressure range due to the fact that R-134 is slightly less efficient than R-12.

The o-rings on an R-12 system are fine for R-134. You should always replace the o-rings any place you open the system just to be safe. Don't try to use R-134 o-rings in an R-12 system as they are a different size and the cross section is different. Some manufacturers are making whats called a retrofit o-ring claiming the rubber is more compatible with R-134....to which I say hooey. R-12 o-rings are fine.

Your 348 system won't suffer any ill effects from converting to R-134. The temperature output at the vents may be slightly higher. (approx. 5-8 degrees) A good R-12 system will easily take the evaporator temp way below freezing even on the hottest day. The R-134 seems to struggle a bit if the condensor temp stays too high and the high side pressures get up around 280.

The only problem converting to R-134 has been converting to the PAG oil that R-134 prefers. Early attempts caused the mineral oil in R-12 systems to react badly with the first PAG oils. Even removing the compressor and draining out as much mineral oil as humanly possible left enough to cause reaction problems. (Draining as much oil as possible from the compressor is still a good idea) The new PAG oil is much more stable and doesn't react to mineral oil in the same manner. If you can find a dedicated R-134 dryer, it works better with the PAG oil and R-134. They have a different dessicant (XH7 or XH9) This isn't a deal breaker, but I definitely prefer the R-134 dryer.

A little note on PAG oil. Toyota (whom I am, of course, most familiar with, recommends ONLY PAG oil for retrofits) But a large number of the other manufactures are recommending Ester oil, claiming it is less corrosive. My experience is that both work well.

Some technicians I know are flushing the systems with a new A/C flush system that I am not familiar with. It seems to be overkill to me as I have had zero problems retrofitting systems (probably hundreds) using my regular methods. I will mention that I usually undercharge a retrofit just a little. Maybe 5% less than what the original R-12 system called for. So if your R-12 system called for 2 lbs, I would only put 1lb 14oz of R-134 in the system. It seems I can get a couple of degrees of extra cold out of the vents.

Last I heard, Auto Zone had a pretty good retrofit kit that included the new R-134 fittings, PAG or Ester oil, and a charging hose. You can get a decent vacume pump at Harbor Freight for about $15.00. If you are up to it, it's not a hard job. The hardest part is draining the compressor.

Now, you didn't hear this from me.......but there have been NO comebacks on systems that have been retrofitted in my shop where the old mineral oil was not removed at all. There are a couple of guys that never drain the old oil out. They evacuate the R-12, add 2 oz. of PAG oil, shoot in the R-134, and ship em.

Like I said, I never said what I just said.

 

Steve,

Thanks for the update.

By the time we're through we may have all 348s running with A/C - or am I being overly optimistic.

Cheers

John

 

Daniel:

Picture 1 - Flap closed, system in recirculation mode
Picture 2 - Flap open, system in fresh air mode

Pictures are looking down, windshield would be at top of photos. The flap would be hinged at the left side of the picture, with the flap moving 90 degrees up and down, pivoting on this hinge. I have seen a post (FerrariTalk?) about a modified piece for the hinge pin. It can break, then the servo moves back and forth without moving the flap. It's easy to break the mechanism if someone pushes on the flap while it is in the closed (recirculation) position. Mine was broken, I fixed it, it has worked for four years now.

 

It's hard to believe that the flap is totally gone, but you never know what someone may have done. If you look at picture 1, you can see that the flap, when it is closed (horizontal), has a foamy surface on top. When it opens (into the vertical position - picture 2) that foamy surface would be facing the interior of the box, on the left side of the open portion. It sits flat against the left inside wall, and flush with the edges.

Nothing there? Any evidence of the hinging shaft?

 

Daniel: Sorry, I've been gone. I'm pretty sure that's your flap down in the bottom of the box, not where it's supposed to be. Look at my second picture, see the oval-shaped deal in the bottom of the box? That's a rubber plug that pulls out. I think your flap is sitting on top of that plug. Can you grab underneath a corner of it, and pull it loose? It looks to me (I COULD be wrong) like your flap came loose and got jammed down in the bottom of the box. Once you get the flap out, you can figure out how to get it back in and hooked up to the servo.