355 AC Compressor clutch won't engage

You can definetly have a part of the ecu not working and still throw out heat. I just went thru that. Only the part of my ecu that was bad was the chip that sent the signal to my stepper motor. I replaced the chip and fixed it. Yours is different situation. If you had your ecu apart and saw a resistor that looked overheated then that's where I would start. I think you need a healthy ecu before tackling anything.

 

Sorry if I'm assuming the obvious, but is there any pressure in the system?

 

Maybe try another hvac panel, perhaps the STOP button is stuck or broken? That will disable the clutch.

 

If the fan motor does work during AC (cooling) ops, but the clutch doesn't, there does appear to be another fuse in the clutch circuit (I'm not sure where it is, but I assume it's near the fresh air inlet box in the luggage compartment). The wiring diagrams (Fig 6) refer to this as "07130".

 

Interesting. I'm trying to find the connection between the cooling fan and the compressor. According to Workshop Manual page I-15, the MIN/MAX pressure control switch on the Drier Receiver is the control switch for the "condenser fan" (i.e. according to that schematic, the left hand radiator fan). However, on page I-24, it states that the MIN/MAX pressure control switch controls the compressor clutch.

However, I can't seem to find the receiver drier MIN/MAX pressure control switch in the wiring diagrams. How did you figure out which wires to short out on the switch? (EDIT: Disragard.... I had mis-labled the pressure switches as "fuses". The symbols on the wiring diagram looked like fuses. Also disregard my previous message on "fuses" ) (ooops)

 

Slightly off-topic. In the wiring diagrams, Fig 6, there are two items labelled ECU (10519 and 10520). Isn't there only one ECU i.e. the one with control knobs on it?

 

I haven't looked up those item numbers you mention, but there is an AC ECU in the trunk on the passenger side of the car

 

Thanks, Lorenzo.

Following your advice, I believe I've found it in the Ricambi parts diagrams (Table 144 (5.2) P/N 64324800), but, oddly, not in the Workshop Manual component location diagrams.

 

look in the electrical part of the wsm

 

No luck, Lorenzo. Other than in the wiring diagrams, I can't find anything relating to the ECU in the Electrical Section. The confusion arose because I found the ECU in the wiring diagrams, but not in the chapter relating to Aircon.

Would you have a reference/page number?

 

Ian, I don't have my Ferrari disk with me. It may be the same as the wsm going around in here anyway, but look on the 3rd section of the wsm. Go to Page 187 and look for 10520. That's the ac ecu. That ecu number is in the very back of the manual along with the numbers of all other electrical parts. Everything can be traced thru here. With this diagram and the help of a forum member, I was able to trace each pin/wire, and troubleshoot my ecu. We replaced a $5 chip and got my ecu working perfectly. I hope this helps ya

 

Sorry.. going around in circles here. All is understood.

In the process of trying to diagnose CarWhisperer's original problem, I discovered that there were two items called "A/C ECU" (according to the Electrical Section of the manual and the number chart in the back of the Electrical Section). When I tried to find out the difference, I went looking in the Air Conditioning Section of the manual. This section only mentions/show the location of one A/C ECU.

Thankfully, your first message clarified what each item was, but the mystery of why the ECU (in the luggage compartment) is omitted in the Air Conditioning Section still remains (and why the centre console control panel and the ECU are both called an "ECU").

Cheers

P.S. Here's my latest attempt at simplifying/clarifying the wiring diagram for the Aircon:

http://www.iinet.net.au/[email protected]/FerrariF355Spider/Fig6_Cooling_Circuit_&_AC_System.gif

 

That's a great diagram of the whole system.

 

Hi guys! I have absolutely same issue. I checked fuses, recharged freon. AC clutch still doesn’t engage. If I put manually 12v straight to the clutch it engaged and starts blowing cold.

I see that the author of the post changed the fan and fixed the problem. But how can this be related if the fan works?

 

The compressor relies on these things:

1) The pressure switch on the receiver dryer working properly (you can jumper the electrical plug to force the compressor to work as part of faultfinding) i.e. the green and green/black wires

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I mean jumper the wires on the car side of the plug, not the pressure switch side.

2) The relay working. You can jumper the relay socket to bypass the relay as part of faultfinding.

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Ignore the 12 volt label. You just need a bit of wire to jumper the relay. You can of course double check for 12 volts dc on pin 30 with the key on (and perhaps the engine running).

3) The HVAC ECU sending 12 volts to the relay coil

4) The "hidden" fuse is ok. If your blower motor is working, the fuse should be ok.

Please let us know how you go.

 

The fan may have been blowing the hidden AC fuse (which is also required for compressor operation)

You said you checked "fuses", but didn't specify which ones. The fuse in the passenger footwell is required for AC operation also, but it also powers the instruments. I assume your instruments are working.

 

Much appreciate for your detailed advice! Issue was with relay. But it's strange, apparently there was a bad contact. I just removed the relay and put it back and everything worked.
You guys are best!

 

Gotta love those cheap fixes

Thanks for the follow up.

P.S. Considering how hard the relays are to get to, I think I would have replaced it. With the weight of the harness hanging from the relay .. and vibration... it may crack the soldering inside the relay.

 

Yes, I agree, I’m going to change it. Thanks for your help.
And unfortunately I have new issue, going to open new thread

 

There are no solders inside the relay so you may keep it. Just make sure its pins are clean (free of corrosion). Unplugging and plugging back in (a few times) relays and fuses wipes off corrosion in the sockets and restores good connections.

 

Is most of it welded? I seem to recall seeing some solder on the coil wires.