Dear FChatters, On my "new" 512BBi (bought renovated nuts & bolts 2 years ago, perfect condition), when trying to put on the A/C, it whistles and it appears that the flange of the compressor shaft, situated front of belt pulley (always running) paginates, say 30/50% of time which you can easily see from the engine bay. Just when you put ON the A/C, nearly no patination for 20/30s but continuous afterwards. The air delivered is very cold when the clutch is secured at start, so I imagine that the refrigerant liquid is full at good pressure. The tension of the compressor belt is OK, so it is a problem of clutch between the 2 mechanical flanges. This clutch, as far as I can be informed is based on a solenoid which "secures" both metal flanges in contact when A/C is on. So, I checked the voltage available at compressor: 12,8V, OK. Indeed when you accelerate (say 2000RPM) the whistle falls slightly or off , probably confirming that the solenoid power is at stake. Before dismantling the compressor from its position (bolts not easily accessible), I would like to know if some Chatter experienced a similar situation, and of course, any suggestion will be very appreciated. Thanks by advance, Jean-Paul
J-P, you said that you have had the "new" 512BBi for two years. Has your AC system always blown "very" cold air with the compressor cycling excessively over these two years since you got it? (I assume "pagination" means the clutch is cycling the compressor on and off.) If it has always been this way blowing very cold and cycling, could it be that the freon charge put in two years ago was a little too much. If the compressor creates too high a discharge pressure with an overcharge, the max (high) pressure switch could disconnect and cycle the clutch as a protective function. (Conversely, if the freon pressure has dropped too low, the min (low) pressure switch will disconnect the clutch, but no cycle.) On my 1986 Testarossa, these switches are at the sight glass. Look at your sight glass during your described "20 to 30 second AC on clutch engaged" period and observe the state of your freon, and when your clutch is engaged if long enough. Is the freon a clear liquid as it should be? Or are there bubbles present indicating that the freon is not completely liquid? If you find you are in an overcharge condition, a little freon can be let down while still maintaining a liquid state through the sight glass. The effect of a slight pressure reduction could reduce the clutch cycling a little bit. Others on this board may let you know what they experience as normal for clutch cycling. Hope this gives you a little insight. EDoug
Thanks Doug for this comprehensive analysis and suggestions. I will check as you say to the sight glass. BTW, I must discover where it is located on this BBi's compressor since I didn't notice up to now. Just to complete the information, I probably badly expressed but I own this car only from January, mentioning that the complete restoration has been done 2 years ago (Zanasi & SG Racing/G.Sala in Modena). Up to very recently I didn't switch on the A/C since cold weather in winter/spring and due to other injection concerns on this car (see other thread about it) . Otherwise "patination" (sorry not pagination) means that the 2 metal flanges of the A/C clutch do not stay "clutched" when A/C is on. Assume that the A/C disk driving the compressor shaft remains against the belt pulley some 50% of time with noisy hissing coming from metal on metal bad friction. Another advice said it could be due to insufficient power of solenoid for efficient clutch. But I checked the alimentation @ 12,9V which looks OK, while compressor's fuse looks OK as well. So, your suggestion about discharge linked to A/C off could be an interesting explanation. To pursue with that suggestion, I could later go to a refrigeration authorised specialist (in France, you must be certified to handle refrigerant), even if probably not acquainted to 512BBi, to check refrigerant volume and pressure. Since I bought the car in auction, I don't know which kind of refrigerant liquid is in? Thanks again for your answer, it helps a lot, I will keep you informed of next steps. Jean-Paul
