BBi air conditioning clutch

I have an older 330 with AC. The power for the clutch goes through a low pressure switch which prevents the compressor from operating if the refrigerant is low. Does your compressor have such a switch? If so, double check the switch and the refrigerant charge.

 

If it's the same as used on the 400, some alternatives are quoted here :

https://www.ferrarichat.com/forum/threads/ac-part-numbers-available.338727/#post-140841466

Probably out of stock in most shops but easier to find with these Ogura references rather than the Ferrari ones.

 

If you directly feed the clutch (green wire on mine) with 12v it does indeed negate the switch.

There are 3 devices that normally shut down this 12v feed :

1. the 3 position fan switch has three outputs for the fan plus a 4th one for the clutch (i.e the compressor does not work unless the fan is running)
   
2. the snowflake button is a temperature sensitive shut-off switch (probe is inserted in the fins of the evaporator)
3. the dryer that acts both as a high/low pressure switch, i.e if the pressure is too low OR TOO HIGH (both ways). Pressure gets high when the evaporator expansion valves closes the freon circuit in order to prevent liquid freon (system too cold) from entering in the compressor.

All this does not explain why your clutch is not engaged when you feed it with 12volts. Note that it requires a good power supply: some twin AC 400i would not work because the supplied voltage was below 10v.

If the clutch mechanism is still working but the magnets or windings are shot, it would be possible to repair the clutch. It is also possible that the afore mentioned expansion valve did not work (sensing bulb badly located or debris from the dryer in the system) and freon in liquid form got into the compressor which seized it and broke the clutch?

If the faulty component is just the magnet/coil, not a big deal, but seized clutch or compressor means you've got to further investigate the root cause. Just my 2 cents.

 

If you have a look here https://www.fleetrite.com/parts/results?query=MA6A+ , there are some MA6A clutches. These do not seem suitable to our cars (we use reverse rotation), but you could probably salvage the magnets and the winding?

 

Another area to look into are the clutch brushes. If they are worn then no power can be sent to the coil. Try pushing on the brushes when activated and note if there is any intermittent action, if so then they are the cause. Since the brushes are in contact all the time even when not using the AC, they continue to wear.

 

The late 330's used the brush type AC clutches, others may have the brushless (MA6A) types. The type with the brushes can be identified by observing the brush assembly held in place by two screws on the top facing position.

 

What is the air gap on the clutch, if the air gap is too large the clutch magnet will be unable to pull it in. .030" works well. Above .045 can be problematic especially as it gets warm.

 

The space between the outer portion of the clutch and the inner portion of the hub.

 

Do you have a volt ohm meter? If so measure resistance of the magnet and if the meter has an amp function read the current draw when you connect the clutch to a battery.

 

The OM schematic for your model shows that it has separate high and low pressure switches at the Dryer:

1. The CN (orange-black) in the harness connected to one of them should be +12V when you have the AC "on".
2. There is a short CN (orange-black) wire running between the two switches.
3. The N (black) harness wire connected to the other switch is the wire that goes to the "+" terminal of the AC EM clutch coil.

To simulate properly closed high and low pressure, just use a jumper wire to connect the CN wire in #1 to the N wire in #3. Alternatively, if you use an ammeter to connect the CN wire in #1 to the N wire in #3, you will make the current measurement in the AC EM clutch coil that Brian suggested. However, you should also verify that the CN wire in #1 does go +12V (relative to ground) when you have the AC "on" -- if it doesn't = you have some other upstream problem.

 

Did you ever make any progress on this problem? Was it just a case of no/low refrigerant (so the low pressure switch was not closed), or an electrical problem with the CN wire not going +12V when the AC is "on", or a dead AC EM clutch coil?

 

Are you saying that the AC compressor clutch was initially engaging, but the high pressure switch quickly opened disengaging the AC compressor clutch (suggesting the expansion valve is blocked)?

 

Been flowing this thread and although I've never heard of a compressor with brushes I found these on eBay perhaps they could be retrofitted. Especially since BBI clutches are nla?
https://www.ebay.com/itm/203600535945

 

Also years ago I had sourced an after market electro magnet for the 328 but I lost all of my literature on it perhaps one could be retrofitted for it from an auto AC supply company. It looks just like the York 328 compressor clutch assembly from Ferrari but yours does have a different part number?