F355 Aircon Recirculation Flap

Does anyone have experience of this failing? A motorised flap moves up to block external air coming in when the button is pressed. It's a common problem, the plastic bushing between the motor and the flap shears. A brass replacement is available from Hill Engineering in the UK.

What's surprising is that the motor appears to be powered all the time the engine is running and is stalled when the flap reaches the end of its travel. There are no limit switches and no timer. Most of the time, the motor appears to be straining against the limit. I'm surprised there's no circuitry in the ECU to detect the higher current when the motor is stalled and switch it off.

Anyone here with the same problem and did you find the motor is powered continuously even when the flap is at the limit?

I'm trying to find out whether it's working as designed or if there's a problem in the ECU.

 

There is also this from Section I in the owner's manual:
Image Unavailable, Please Login

 

Thank you, so that shows the flap motor is not simply hard-wired to the recirc switch on the centre console; the microprocessor (assuming there is one, this is 20+ year old technology) can also activate the flap but because there are only two wires out to the motor, there's no positional feedback and it does look like the motor is permanently powered one way or the other. Doesn't seem to be good engineering practice to have the motor stalled like this since opening and closing the flap takes only a couple of seconds.

It might even be the case that it was intended to switch the power off after a few seconds but there's a bug in the firmware without any means of fixing it.

 

hello all,.. i am currently also fighting with a damaged flap. I measure 12V and -12V contiounsly when pressing/releasing the recirc button. I then disassembled the motor actuator and found 2 internal plastic gears damaged,.. one damaged gear was repaired by the previous owner, but one is not repairable...

in my opinion... there is a (too big) torque multiplication with total of 3 gear sets,... and also the motor itself with 12V and zero rpm already gives quite some torque...

i ordered now a spare actuator from a fiat coupe but i am very worried it will break in no time again...
and if it does not brake,.. then the Square-d/shape connector will brake soon (for which the hill enginnering solution is luckily available...

 

I think that the Recirc Flap motor is (should be) controlled/stopped by a current sensing circuitry, otherwise something will break as it produces pretty high torque on the square shaft. Perhaps it fails (breaks) when something goes wrong with the current sensing circuit in the ECU. If such circuitry was not included by ECU design, than it was a very bad design.

Anyhow, I had to add two limit switches (including two diodes) to the Recirc Flap motor as I built my own "analogue ECU" (to replace the failed original) and I did not bother to add an overcurrent circuit for the motor. It was fairly easy to attach the switches to the motor and it works perfectly well. I will post some pictures and the limit switches wiring diagram over the weekend.

 

would be great if you could sent me/us some pictures and wiring diagram.
could you also mention which type of limi

 

... limit switch type you used.

i guess you put a NC limit switch paralell to a diode and the same set for reverse?

 

About a week after I took delivery of my 355 I noticed a continuous wrrrr-click-wrrrr-click sound coming from the luggage compartment. I tracked it down to the recirc flap motor running continously with the famous broken shaft (that hill makes the replacement for). Anyway, I disconnected the motor and have never, ever given it a second thought. That was 11 years ago and can honestly say that I have never missed it.

During that time I have lived in Southern Italy, northern Italy and now Madrid (where incidentally we are having a historic heatwave, hottest it's been in 150 years).

I think the AC works pretty good, considering the amount of (imho unfounded) criticism it gets and I'm not convinced recirc would make that much difference.

 

does abyone know by chance which type of plug this actuator is equipped with? i wanna built in some additional stuff without cutting open the original harness and therefore need a female and male side of this plug...

@spaghetti_jet: during the recent heat period in switzerland with up to 38degC i wished i could switch to recirc just to get few degree less in the cabin (or switch the fan one number slower to avoid the noise)...
Image Unavailable, Please Login

 

Replace the motor, they get weak and will not work. Just did one

 

Hi "salbrech",

I used mini limit switches which have both, NC & NO contacts. I used the NC pair of each limit switch, bridged with a diode, to cut the supply to the motor, the diode to allow reverse flow after the contacts open at the end of the travel. The NO pairs, I used them to power up (via a 1K resistor) the small LED-s on the ECU push buttons to indicate open & closed positions.

I attached both limit switches to the outside of the motor housing and inserted a thin aluminium "finger" (pointer) over the rectangular shaft to activate the limit switches. As I am away from home now, I can only post some pics over the coming weekend.

 

thanks for that advice,... had exactly the same in mind.. however the limit switches i ordered now are NC only,.. so the indication part can't do them ( I do not wanna pull new cables )

will also post some fotos once done...

many thanks again,.. best forum by far

 

The pics show how I installed the limit switches for the recirc flap motor. I made a pointer of aluminium with a square hole to fit snug over the motor shaft. To allow space for the pointer between the motor and the evaporator wall, I inserted washers below the motor mounting points. I made the pointer like a fork (2 fingers) so that I can separately fine tune the flap closed and opened positions by bending the forks (the open position is actually not critical). You can see that the fork fingers are bent at 90 deg at their tips to act on the arms of the limit switches.

The connection of the switches is very simple, inserted into the two wires going to the motor. The diodes can be 1N4003 to 1N4007 as the motor draws less than 100 mA.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

hello Mr Stojanovic,
I went now for this setup. My limit switches will sense directly the flap, and not its axle....

Hope to gain some accuracy with that, but of course I need to drill into the plastics of the HVAC box,...

Best regards, Simon
Image Unavailable, Please Login
Image Unavailable, Please Login

 

I wish I was that smart. You show how, and I still couldn't did this. My flaps broken too. Ahhh Fresh air

 

hey Skippr1999,

I am so smart, it took me 1.5 years to realize mine is broken

Simon

 

Salbrech,

Your wiring diagram is fine except that the current to the motor will always flow through one of the diodes. If you wire as per the diagram I showed, the current will flow through the diode only for a short period of time until the open switch contacts close again.

 

To be honest, I was asking myself quite some time which one of these two options is better,... could not find any pro or cons though....... :-(

I studied mechanical engineering and therefore not electrical engineering.... guess I am little aware of these fine details

I'll use your proposal then, seems your quite good in electrical stuff

Best regards from Switzerland
simon

 

installed today the setup with 2 limit switches and 2 diodes, sensing directly the metal of the flap. On the area around the limit switch, I removed the foam.

sorry for the bad picture quality

PS: the blue thing is liquid sealant on the back of the limit switch
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Coming back to this after the summer, it's good to know that everyone's ECU is doing the same thing and I agree it's bad engineering not to switch off the motor ever.

I had thought of putting in a timer which would power the motor for, say, 10 seconds when power was first presented to it or when it changed polarity but I agree limit switches and diodes are a better option.

 

While this thread is active I though I'd contribute. The AC flap never worked on my car since I bought it. It never bothered me since the car is a spider. But with colder weather I thought I would take a look. I pulled the motor off and all external pars were fine. The motor sounded like it ran but the shaft would not turn. So I opened it up and found this. The reduction gear (red arrow) that drives the shaft gear was sheared off and in pieces. The motor ran fine, but there was simply nothing to the shaft so it would not move the flap.

While I'm at it, in the second picture does anyone know what the circled fuse is for? As you can see, there is a relay in that position but the fuse is missing. Everything seem to work on my car so I' at a loss as to what it is for, what amperage is correct, and even if there should be a fuse there??? This is the fuse block on the right hand side of a LHD car, to the right of the AC box and near the hood latch.
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Yes, an empty fuse socket is inviting but there should be no fuse there (the white dot on the relay tells you that). A fuse is inserted there only during ABS diagnostics, have a look at the Workshop Manual.

 

Got it. Thanks.

 

Ordering new motor from AW Italian. Actuator (for Evaporator)

 

Surely the biggest problem with the recirc flap is it's weight. It feels like a steel plate with two sheets of heavy rubber attached. How are plastic gears supposed to drive this without problems? Is it this heavy for a reason?

I just found my plastic drive shaft sheared. So much for PPI's

Anyway, thanks for the tips on replacements/fixes, gents

Cheers
Ian.