360 A/C Control(Temp) Switch

It could be the ECU.. mine was bad when I bought my car. Does the temp indicator (second button on the left iirc) give the accurate temp outside? If its funky it could be a bad ECU. Alternatively, it could also be the cabin temp sensor that has gone bad. BTDT!

 

Can you get a resistance reading from the temp control switch, i am assuming it is a circular switch which adjusts the temp. If you can get the wires disconnected, then connect a multi meter on ohms setting. Turn the switch full circle and see if you get a steady change in the reading. Unsteady jumps in reading should not happen. Can you get access to spray contact cleaner into the internals of the switch. Some of these switches have a wound coil of wire which the adjustment pick up on, if dirty they stop working- just depends on what type it is

 

Finding the right combination of 8 pins might prove challenging. However, looking at the wiring diagrams for the F360, the first 3 pins seem to be the same as the F355:

1) earth
2) background lighting power in
3) 12 volts key power in

If the pattern continues, here are some of the other pin assignments on the F355. They all go to the HVAC ECU (as they do on the 360).
4) unknown
5) temperature setting (voltage out, ranging from 4.9 to 0.042 volts)
6) STOP
7) unknown
8) Recirc

Image Unavailable, Please Login

If you want to get a voltage out on pin 5, put 12 volts power on pin 3 and an earth on pin 1.

 

Looking at the spare parts diagram, it looks like the temp switch comes with others in a complete housing- this multi pin diagram must be the wiring to the complete unit. It is just going to be trial and error to find the 2 that connect to the temp switch and see if its resistance changes with adjustment. The fact that temp adj is 4.9 to 0.042 backs up my idea that it is a variable resistor device. Pull the cable out and see if u can pick up a variable ohm reading on a pair of connectors. A new unit is mega money

 

Or get your hands on a known working control knob unit and plug it in.

I have a spare but I’m in Houston.


Swap w another 360 buddy?


Option 2- I just had my control knob unit out due to knobs falling apart. The control boards are super fiddley. You might be able to see a plug or wire loose upon visual inspection. Have a look.

 

No doubt, but note that the F355 panel has a bucketload of resistors and tiny detents on the rotary switches which may mean a non-infinitely variable resistive system. i.e. a stepped temperature control system.

I would try checking the resistance between pin 1 and 5 as a start. If no reading, perhaps try a combination of the 5 wires going to the ECU

 

The 360 panel is a rotary switch with multiple resistors. As above.. it’s stepped.

 

You just have to guess which one. There are 5 temp sensors, including the outside temp sensor.

If you need a wiring diagram, let me know. Spider or coupe?

Check to see if the interior temp sensor suction fan is working on the lower dash. You may be able to hear it running. If not, use 1 ply of tissue/toilet paper against the inlet to see if there is any suction. If the fan is not running, the sensor just cooks in its own juices rather than sensing interior air.

Image Unavailable, Please Login

(EDIT: Wire colours shown above are on the car side of the plug, not the sensor side of the plug. The HVAC ECU is most-likely supplying the sensor with 5 volts on the pink wire).

 

Here's one for the Coupe.

https://www.dropbox.com/t/cudUQLQsNx1Gow0y

If you preview it, then hit the print button once or twice, it will convert the image to a pdf file (if you have problems viewing gif files).

Don't let its size intimidate you. Start in the middle and look for the pale blue components. If you have problems figuring out how to check the sensors, I can always break up the image into smaller components.

Note that there are also two treated air sensors as well as the cabin air sensor and "sun radiation" sensor.

 

Actually, I made them myself using the shop manual wiring information. Here's the one for the suspension

https://www.dropbox.com/t/igP0QngPuPqX8PNa

Some of them are a work in progress. e.g. I'm not sure of the internals of the brake pedal switch (for the double contact version). I thought both contacts would be normally open (until you pushed on the pedal), but the diagrams for the F430 show a double contact switch which has a normally open switch and a normally closed switch. The F430 switch has a different part number, however.

The shop manual is still useful as it shows you where the plugs are and where the harnesses run.

 

Nice happy ending wo pulling out the wallet!

 

Yep, I love a happy ending... especially a cheap one.

I may have to check my cabin temp sensor for dust. By the way, are the sensor fan blades audible on the F360 when the fan is running?

Good guess (avionics maintenance engineer in a past life). Boeing 747's have a similar cabin air temperature sensor which also uses a suction fan. I've even found one blowing in the wrong direction. The fan was mounted upside down.

 

The power setup is probably just for simplicity. On the F360, heating is still available with the A/C off, so perhaps some of the automatics are still available which use the sensors?

e.g. The manual says that if the outside air temperature is cold on startup, the fan air will be directed towards the windshield rather than blowing it in the driver's face. When the heater warms the air to 35 degC, as sensed by the Treated Air Temperature Sensors (not the Cabin Air Temperature Sensor), the air is distributed as desired. I don't know if this system is active on the F360 with the STOP button selected. I can't test this on my F355 because the STOP button closes the hot water valve.

 

I won't let that go to my head (much)

As I was saying recently, the wiring diagrams do tell me how things are hooked up, they don't tell me what's going on inside the computers (or in the minds of the designers).