A/C Cut Off Suddenly

Just got the car a couple of days ago and the AC was blowing strong and cold having been completely rebuilt about a year ago.

It was working fine most of today when on full blast but for about 3 minutes it began blowing air temperature air before the fans stopped entirely.

The car is going in for inspection next week but I’d be curious if anyone has had this issue before and might have ideas about what may be going on. Seems electrical given that all just stopped suddenly, but honestly I have no clue…

 

Don't sweat it! Dave will fix it. Any number of things it could be. A/C is relatively simple with many potential failure points. We are much more likely to see failure in limited use cars. All you can do is hope for one of the more simple failures. Ferrari has never been known for robust A/C.

 

What parts were rebuilt? Is this on your '95 F355?

By fans, do you mean blower fan (singular)?

I assume the compressor stopped working for some reason. I think your refrigerant pressure is ok. I don't think low refrigerant would cause your blower fan to stop running. Similarly, I don't think a faulty compressor would stop the blower fan. Like you, I'm more inclined to think an electrical or ECU issue. Something overheated/melted.

Most of the electrical stuff is hidden under the frunk carpet (including the ECU). There is an AC system fuse in the passenger footwell, but that will be ok. If that blew, you would lose your instruments. Have you heard of the AC system "hidden fuse"? It's possible that was progressively melting and shutting things down one by one. Do you know if it was replaced by something more robust (such as a bullet fuse?)


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Yup, my car. Here is the work previously done on the A/C:

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That's far from a complete rebuild of the A/C system. You got a system recharge and a fuse holder replaced. You could have an entirely new fault or a repeat. It is possible for example that a bad connection or wiring somewhere else in the system is pulling too much current and causing the failure. If there is less than a full charge after only 1 year since charging you have a leak.

 

It's good to see that the fuse/fuseholder was replaced with a maxi fuse/fuseholder. If the system is pulling a lot of amps, then perhaps the fault has shifted to the next weakest link. I recall seeing a photo of a melted HVAC relay holder 6 (?) months ago. Check the forward relay holder.

If the components weren't so hard to get to, I'd get some current values for you for comparison. I just bought a fancy new dc ammeter. Maybe Miro @m.stojanovic has some values for you?

 

Doesn't your system show an "E" code on the display? These help to diagnose the specific failed item. Mine, for example, showed an E1 code which points to the passenger compartment temperature sensor, a ***** b/c it's behind the dash under your left knee, buried of course.

 

It's a 355. It doesn't have a display

 

I have not measured the amps drawn by the 348's heater blower motor but it should be around 10 Amp when at full speed. Overheating/burning of the connections at the hidden fuse or in the relay sockets could be for two reasons: 1. the blower motor or the compressor clutch (or both) is drawing excessive current and 2. the connections have developed some resistance due to corrosion.

In the case of loss of power the the blower motor, the first thing to inspect is the hidden fuse and the two AC related relays next to it, as shown on the picture posted by Ian. Here's a picture of these components on the 348:

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This is a typical example of burned fuse and overheated/burned connection on the fan relay in a 355:

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This seems to be an appropriate thread to hijack::

Yesterday, I was out driving my F355 and the A/C was running blowing cold with the fan on 2 (earlier in the day it was on 'auto'). After about and hour of driving around, the fan went dead. And now 3 and 4 run the fan, but 3 runs the fan very weak while 4 runs the fan like 2 used to run.

A/C still blows cold, just a fan control issue as far as I can see. Not blowing 'auto', 1, 2. Blowing 3 = weak, 4=moderate.

Did the rotary switch fail, or did I loose a pole on the fan motor ? Something else ?

 

There have been identical symptoms in some forum threads. The hard part is finding the old thread. The panel doesn't fail that often. Fan speed commands just involve a resistive network in the control panel. It's more likely to be a fan speed regulator/controller (P/N 63307200... which is most likely NLA, but usually repairable) or the HVAC ECU in the frunk.

Anyway, to check the control panel:

FAN SPEED (using pins 3 (fuse power) and pin 8)
AUTO 191.1 k ohms
OFF 73.3k ohms
1 22.86k ohms
2 14.77k ohms
3 9.81k ohms
4 7.22k ohms

FAN SPEED (using pins 1 (earth) and pin 8)
AUTO 183.7k ohms
OFF 66.0k ohms
1 15.5k ohms
2 7.44k ohms
3 2.475k ohms
4 1.2 ohms

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Miro (@m.stojanovic) has a technique for checking the fan speed controller (involving jumper wires):

https://www.ferrarichat.com/forum/posts/145547685/

Miro makes controllers and there is a company in the UK which repairs them.

There are plenty of threads on replacing ECU chips. Chip assignment is shown here (thanks to @Zamboniman308) :

https://www.ferrarichat.com/forum/posts/147991197/

Siemens IC chip P/N TCA2465G

However, sometimes the damage is not limited to the chips on the boards.

https://ameblo.jp/j-wave2004/entry-12383909220.html (use Google Translate to convert to English)

All rather labour intensive.

 

Thanks.

 

i had a similar thing happen to mine recently. i thought it might have been the fan resistor. Had the op amps replaced and then the fan speeds worked fine again. So it may be the HVAC ECU causing this.