355 Climate control dead

If you get battery and ignition volts on the front relay, pull the aft relay and see if you have 12 volts on relay sockets 85 or 86 (with the ignition on).

Hopefully all these power ups is not flattening your battery.

If you have volts on that aft relay socket, try swapping over the relays (assuming they are the same type) and see if there is any change in HVAC control behaviour.

 

Thanks. I'll add these details to my diagram.

Interesting. I'm not sure what to make of the 0.3 volts on pin 30. Perhaps voltage is coming through the fan speed controller ([10008] in the diagram)???

Anyway, you seem to be getting voltages in all the right spots. I'm worried there might be an HVAC ECU issue. Since the 30 amp fuse isn't blowing, it's unlikely the blower motor is killing the entire HVAC system. Did you find the HVAC ECU during your investigation?

 

Updated diagram here (with some relay pin numbering):

https://www.dropbox.com/t/8l5HDohVodFOiHkL

I don't yet have enough information to label all the pins on the aft relay.

 

Going back to your original post (ooops). Now that I remember, the HVAC ECU is located next to that plate you removed. I guess it is possible your first thought might be accurate.

HVAC ECU here:

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Check the ECU connector for security.

 

BTW this requirement works "really well" in 107ºF heat in Texas summertime.

Cooked if you open the window, cooked if you don't.

 

See item #46

https://www.eurospares.co.uk/Ferrari/355/355_(2.7_Motronic)/PartDiagrams/143/Evaporator_Unit_and_Passengers_Compartment_Aeration

 

The control panel can be difficult to diagnose. Some parts of it seem to be passive resistance networks feeding into the HVAC ECU, other parts seem to be more complicated.

This thread discusses resistance values measured across certain control panel connector pins (read the whole page for amendments/additions)

https://www.ferrarichat.com/forum/posts/148650231/

From (vague) memory, the blower motor runs automatically even if the control panel is removed.

 

As I explained earlier, the two buttons (lighting) use a different fuse. Refer to the diagram:

Pin 2 is for button lighting (yellow/red wire). Power from fuse 12
Pin 3 is for panel power (green/white wire). Power from fuse 25

Ignition turned on in both cases.

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Fuse numbering and wire colours applicable to Motronic 2.7 car only

 

I'm still leaning towards your ECU.

If your panel plug is still accessible, try powering up the HVAC without the panel connected to see if the fan runs.

Bon appetite

 

Here's another view of the HVAC ECU (thanks to @eric355 )

 

I believe that's the ABS brain box.

 

Ah.. I thought Eric provided us with a Euro (LHD) photo. Or do you have a RHD car?

I guess your ECU wasn't disturbed then (but can't be ruled out entirely).

 

This looks like a contender here:

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It should have one yellow rectangular plug and one white rectangular plug (EDIT: I thought they were the same size, but I may have been thinking of the Suspension ECU)

The white one goes to the control panel (13 pin)

 

Another possibility: The difference in location may be due to the type of braking system you have (Teeves vs Bosch)

 

I know but idea is you can get home safe in any weather.