cabin ventilation control ancilliaries locations.?

Hey,

can anyone say whereabouts the cabin heater/ventilation system control unit is specifically?

As opposed to; "in the dashboard'!

in particular (with reference to the schematics);

328- heater / climate control unit

thankyou

For a 20v/t , in passenger footwell:



Assume the same on VIS but not 100% sure.

THANKYOU Graham-

actually, it was for Simon's VT, so that is great.

interesting to see the diagnostic socket- what plugs into that..? Was it a special FIAT tool..? I wonder what visibility it gave of the system...?

Incidentally; do you know if the cover over the top of the motor-control-variator (/ fan-resistor), is removable in situ..?
I was going to pull the feed-line connector out of the cabin ventilation fan; but the connector seems to butt straight up against the cover on the motor controller, which is bolted to the fan.

Also- do you know if the climate ECU is just the one screw holding it- at the bottom..?

I've just swapped over the ecu but the effect is identical - i.e. the heater fans will only operate on AUTO when the temperature is set to MIN or MAX.

On my mate's 20vt. also P reg, the fan will operate at all different temperatures...


I wonder if there's any mileage in swapping out the largish 4-tongued (that part is "buried") unit just behind the ecu on the bulkhead...

Cabin temp sensor behind the little fan on centre console dirty or failed maybe? Or the fan that feeds the sensor failed or clogged?

There's also this "how to" about fixing the fan speed switch, maybe also applies to the temp. selection:

http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1373896

Not sure what device plugs into the climate diag socket. I don't think it's a generic device for all systems (eg. the sykes multi pod only handles ECU, ABS and airbag, but not climate) , the only reference to it I can recall was a specific device just for climate systems and wasn't made by Fiat.

Yep these are go-to's.....I've had the console out and checked the fan which works fine, also the 3 brass "finger" contacts which are nice and clean.

Next step if possible would be the diagnostic socket but will try the swap-out of the other part I referred to above.

Are the low fan speeds all working OK on manual?

Yep, so I'm fairly satisfied the problem isn't at "eye level".....

You can probably do some basic diagnostics on the temp sensor with a multimeter, assuming its resistance changes with temp. which would be typical, but even if it's the voltage output 3 pin type.

If the "other part" you mean is the fan resistor all that does is reduce the fan speed to the pre-set levels.

Indeed you know my non-tech jargon too well Graham, the fan resistor which you have pointed out in your photo.

I have a spare temp sensor as it happens so perhaps I'll go back to testing this out with the multimeter.

I've swapped my temp sensor with the spare I had from a '98 20vt and the resulting Auto fan speeds are identical to the extracted one.

The resistance in the spare (across the two "legs", grey and grey wires) was c.2700.

One next step would be to check the two greys at the climate ecu (pins 3 and 4).

Now wondering whether there may be a fault behind the temp control knob itself.....

I do recall the "auto" setting being garbage on my 1st coupe from new and basically not using it + others agreeing at the time.

In current coupe I normally leave the fan at 0 and just switch to 1 or 2 manually when required.

Hold the temp sensor between your fingers to heat it when testing and see if the resistance changes.

Is the "heat" selection dial working at each point all the way around when the fan is switched on manually?

1.That's interesting..
2.Likewise
3.That's also interesting
4.Yes I would say it's quite sensitive - in other words you're leading me to believe that the workings behind there are probably ok.....

Did you check for any other dodgy wires at radio mounting frame?

I think the climate ECU needs various sensor readings to work in the "auto" mode so maybe a bad connection or failed sensor?

Think someone said auto mode didn't work if the temp. sensor in the mirror was disconnected for example. Also the auto mode should wait until coolant has warmed up before controlling fans so if that sensor reading was cut it could also stop things working as intended.

My advice would be to go directly to climate ecu plug and start checking with multimeter all the inputs first, get the wiring diagram and the pinouts printed for ease of use. The AutoData also gives the values for sensors and etc. if you have access to it. As for the temperature selector, iirc, it's just rotary switch with resistors in series, incrementing X ohms per degree °C selected, one bad connection would give open circuit. The diagnostic could be made with the Fiat propriety tester, but, also iirc, the diagnostic procedures are the very basic ones from the past - blinking led, just can't point you in the right direction where to find info now. Think all fiat made cars/vans from that époque share common system (speaking when it's really the same system, not full auto a/c or just manual on/off a/c).

Sorted!

Thanks to Graham's suggestion of the mirror sensor we had a look at the wiring


3-wire connector = up/down, side to side movement
br/blk connector = mirror heater
2xpink connector = sensor for climate control


On closer inspection there was only one pin visible in this last connector - the solution was simply to push it back into place ....



And voila - I have working climate control

Thanks as ever to DG for the electrics hands-on