F355 HVAC ECU

There may be a way of checking the stop button by removing the panel, powering it up with 12 volts and checking the pin outputs. I'm trying to interpret the notes Skiday posted on his car's HVAC panel:

Of interest to you:

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Power the panel using pin 3 (positive) and pin 1 (negative/earth). Then do a voltage check between pin 4 and pin 1.

If you are getting a voltage change on pin 4, then we can probably move on to the HVAC ECU.

Interesting (to me):

Pin 2 is panel backlighting, but it looks like the STOP button illumination uses pin 3 power. Perhaps the recirc button also uses pin 3 power.

 

Just realised that Skiday's panel's STOP button illuminates with the switch up, which is opposite to mine. The manual says switch "released" (up), the AC should work (which it does on mine). There does seem to be panel differences, however, regarding when the STOP button illuminates.

On aircraft, a dark cockpit = a good airplane. Do you want a car which has a bright light telling you where to find the stop button or do you want a car which which doesn't have any distracting lights when everything is running ok?

 

Yes I got another HVAC board and will swap it this weekend.

It seems like it is the STOP button that's malfuntioning. Definitely seems like it's stuck in STOP/down position.

 

Ok so I swapped the old boad with the new one I bought on ebay.

So now my AC and heater are finally working. but my air direction now only blows in the defrost postition. like Cmon!!!!!

So the AC not working with the heater was the STOP button not being functioning. The STOP button was damaged seems like and caused this whole issue.
But now my air direction is stuck in one setting, I wonder what's wrong with that???? It was fully funtional witht the old board after I replaced those 6 chips in the AC ECU.
I did disconnect the battery terminal for a day and still it didn't help. Hmmmm wonder what is causing the air direction to be stuck in one position. It seems like it always gets stuck in the defrost position as I remember people were mentioning.

 

Assuming your new board is ok...

What was the outside air temperature and how long did you let the system run (until the coolant was warm)? The system is designed (at least in AUTO, not sure about manual) to not blow cold air directly on your face on cold days.

Perhaps the outside air temp sensor is faulty and is always showing a low temperature. I don't know if we have any resistance values for the sensor at particular temperatures. Check the forum for references to outside air temperature.

I'm not sure if there is any easy way to access the sensor wiring. Is the ECU still accessible? If not, it may be best to go through the driver's door plug.

Sorry, running out of ideas.

 

Ian, I don't think it's the temp. sensor or anything related to that.

The thing is I had my air direction fixed with the new chip in the AC ECU. It was working all ok once I redid the chips. Now once I put the new control electrical board it suddently stopped working. Strange stange.
So I decided to put the old board back in and see if the air direction would start working again, and now with the old board in it's not functioning as well.
It's like this HVAC has a mind of it's own! Honestly im tired with it and about to give up and just drive the car like that.

So the weridct is, it's not the board that's not working for the air direction, it's who knows what it is now. Could it be the chip went out agian all of the sudden, or the air direction little motor that controls the directions went out??? One of those two most likely.... but what are the chaces right? it was working perfectly before the new board. And even now I put the old board in to see if the air direction works as before, and it's not.
Hmmmmmm I will do some more tests and hopefully I can find something.

 

@Shurik355 my local Ferrari dealer said they had experience of plugging a known good ECU into a car, running it, then replacing with the non functioning ECU and it magically came back to life, obviously didnt work on mine though lol
Not sure Id believe it if it wasnt a dealer saying it (and they havent been great in their support TBF) but might be worth a shot?

 

Alex (Shurik) found that his direction motor has crumbling gears. Hopefully it's not blowing up the board.

I think he's having problems finding a new one.

We just need to find someone who can carve these out of titanium ...

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That's not too dissimilar to my experience - I took the board of of the housing, couldn't find anything wrong with it, so put it back, and it started working again.

 

Yes those gears in those motors get broken easily. They brake and they blow the chip in the AC ECU. Im sure of that now. Those motor gears tend to brake the gears causing the chips to burn.
I just need to find the replacement.

 

An interesting development here...

https://www.ferrarichat.com/forum/posts/147607798/

 

Now its been working for a few weeks I think its safe to post ..........

I have a 96 F355 and this issue came up a little while back, thank god for this forum as Ferrari UK were absolutely useless in giving any advice at all to the point they actually failed to report the results of a functional test correctly. Twice. Jesus wept.
This is before I mention they also managed to damage the car both times it was in with them and sent it back with warning lights on, no fuel, the coating removed from the windscreen surround, thanks Jardine Ferrari Colchester.

Anyway, on my car the hot/cold flap stopped working so it would blow aircon but not heat - it was fine in summer but was going to be a bit chilly in winter. Chips are indeed Siemens TCA2465G and I found them on UTSource for $2.50 each plus shipping and tax from Hong Kong.

Took them to an electronic specialist I know but he wasnt comfortable with removing and replacing (they need a fair bit of heat apparently) but found another guy who did it for me - first time he tried all of the functions were knocked out (he predicted this), second time was the charm and it seems to be functioning correctly.

Relieved doesnt cover it, whoever contributed to this thread wont ever need to buy a drink if they are with me, thank you!

 

Just drove down to Melbourne and back today to pick up HVAC ECU. Had all 6 IC surface mount chips replaced. No more gremlins. Full system operational. Works perfectly. Very happy and worth the 9hr drive

 

Who did you use?

 

Elliott can you PM me on this one please mate. The guy generally doesn't do repairs he is a manufacturer of boards. If you need it done and he agrees I can pass the info on to you. A1 phone repairs in Melbourne also offered to do the job for $70. Cheers Paul

 

Can anyone confirm the ECU from the 360 works in the 355? the part number 875240 is the same and the seller i bought it from claims it works, however i'm skeptic as the new ECU does not work either.

I have checked the heater valve and it does work when applying 12V manually.

 

i would put money on it that both ecu are bad. Id send it out to get new chips on it. or if your a diy its easy enough

 

What do you mean by “work”? Heat is coming through the vents? Actuator- motor running? I have heard of a valve internal failure, so getting heat is the only true test of a valve (and water pump)

Does the new ECU have exactly the same behaviour as the old one? It seems unlikely (but not impossible) that a new ECU would have the same fault.

 

Yes heat is coming out from the defrost vents and the motor turns if i apply 12V externally.

Without the ECU it would blow out from the front vents, with the ECU it's only blowing thru the defrost outlets.

However i only get heat with both the new and old ECU, only things working from the control panel is the STOP button and the blower fan control.

 

Just checked on Eurospares. The part number for a F355 HVAC ECU is 64324800

The part number for the F360 is 204068 (which appears to replace 168937)

Now that I think about it, the two cars are quite different. Different air distrubution system, different sensors, different outputs, etc.

 

My 355 did the exact same thing And it was the chip in the ECU. The heat was always on because the ECU would not let the bypass valve turn it off

 

Where did you get the 875240 part number from? The old unit? Is it a manufacturer part number or Ferrari part number?

Sorry, I thought you were having problems getting heat. I just remembered you are now in summer in the Northern Hemisphere. Are you saying that you have heat all the time, but not necessarily in the right direction?

If you lose heat with the STOP button, this would prove that the valve and perhaps even the driver chip is working. The valve provides position information to the ECU and the driver chip will provide power to the heater valve to close it (until it is fully closed).

 

It's a manufacturer number on all these units.

Yes i have heat all the time., i will test if i get power from the ECU to the heater valve.

I don't trust the control panel either as some previous owner put a separate single wire on to the circuit board, don't know why.

There is no problems with the AC compressor as they filled it up with R134 and tested it manually and cold air came out, they thought it was the ECU, but the replacement ECU from a 360 is not working either except fan speed control and STOP button.

When i didn't have any ECU connected the air came out from the front vents, with new ECU connected the air comes out from the defrost vents.

 

Interesting. I wonder if it's programmed in some way. Perhaps by software, dip switches or earthed pins.

I would make sure that the valve is still in the circuit (as the ECU needs this for position).

Seems to be a recurring theme on the forum. I'll be carrying out few tests on my own car shortly to try to confirm the operation.

 

Maybe send one of those units to a friend of yours to try it on their car. Those ECU's are a simple plug in.