I decided to do my own resistance checks and almost none of my results matched what I was given by a fellow Ferrari owner. I still can't make any sense of the results, however. The resistance networks have a relationship between both panel earth and panel power. Note that there is some variation depending on the ohmmeter used. FAN SPEED (using pins 3 (fuse power) and pin 8) AUTO 191.1 k ohms OFF 73.3k ohms 1 22.86k ohms 2 14.77k ohms 3 9.81k ohms 4 7.22k ohms FAN SPEED (using pins 1 (earth) and pin 8) OFF 183.7k ohms 1 66.0k ohms 2 15.5k ohms 3 2.475k ohms 4 1.2 ohms TEMPERATURE (using pins 1 (earth) and pin 5) Max cold 3.143k ohms 18C 3.071k ohms 19C 2.945k ohms 20C 2.797k ohms 21C 2.620k ohms 22C 2.408k ohms 23C 2.149k ohms 24C 1.822k ohms 25C 1.357k ohms Max heat 1.2 ohms TEMPERATURE (using pins 3 (fuse power) and pin 5) Max cold 291.3k ohms 18C 98.0k ohms 19C 47.5k ohms 20C 30.72k ohms 21C 22.26k ohms 22C 17.29k ohms 23C 13.98k ohms 24C 11.61k ohms 25C 9.83k ohms 26C 8.42k ohms Max heat 7.33k ohms DIRECTION (using pin 1 (earth) and pin 7) Auto 184.0k ohms Feet 65.8k ohms Feet/Head 15.52k ohms Head 7.46k ohms All vents 2.481k ohms Demist 1.4ohms I forgot to do pins 3 (fuse power) & 7 for air direction. The STOP and RECIRC was a strange one: (using pins 3 (fuse power) and 6) No STOP + No RECIRC = 6.60k ohms NO STOP + RECIRC = 3.192k ohms STOP + RECIRC = 4.68k ohms STOP + no RECIRC = 4.68k ohms Using pins 1 (earth) and 6 No STOP + No RECIRC = 3.922k ohms NO STOP + RECIRC = 2.642k ohms STOP + RECIRC = 4.66k ohms STOP + no RECIRC = 4.66k ohms Pin 4 also had a strange relationship with STOP and RECIRC (both in combination with power and earth). It's interesting to note that the fan operates without the control panel hooked up. With ignition turned on, first it would be on low, then switch to high automatically a few seconds later. With the panel completely disconnected, I could not measure any power coming from the ECU to the control panel plug (which I thought odd). I confirmed this. So in summary. Pin 1 = earth Pin 2 = panel lighting Pin 3 = fuse power Pin 4 = function unknown other than being affected by STOP and RECIRC Pin 5 = temperature Pin 6 = function unknown other than being affected by STOP and RECIRC Pin 7 = air direction Pin 8 = fan speed
Missing piece: AIR DIRECTION Values for pins 3 (power) and 7 Auto = 184.0k ohms Feet only = 65.8k ohms Feet&head = 15.53k ohms head only = 7.48k ohms All = 2.500k ohms Demist = 19.2 ohms
I jumped a cable between pin 2 and pin 3 in the fan power unit connector and the blower worked at full speed when ignition turned on. However I found some crazy stuff, i removed the power unit and look at the photos Need to get a new unit..... Image Unavailable, Please Login Image Unavailable, Please Login
If the circuit board hasn't been damaged, Miro should be able to help you replace components for improved longevity/performance. https://www.ferrarichat.com/forum/posts/144889953/
Somebody's creative solution. You can open it up (follow the threads from #53 on in the link provided by Ian) and see whether the small circuit board inside is still intact. If it is, the unit may be repairable but it looks like it has lost some of its cooling fins. If the unit is beyond repair and you cannot find another one, I can send you a controller which I build by modifying/adapting an existing similar unit (made in Europe and used in some French cars, not a China knock-off) which is much more powerful than the original unit because it uses two very powerful MOSFET transistors, 75A and 285W each, to control the fan motor. It also provides PWM control as compared to analogue by the original. The "donor" controllers I use are used, not new, but tested and in very good working condition. Converted units look like this: Image Unavailable, Please Login
I have now measured the fan speed on the control panel. It seems to work and i get the following FAN SPEED (using pins 1 (earth) and pin 8) OFF 65.5 KΩ 1 15.47 KΩ 2 7.46 KΩ 3 2.48 KΩ 4 0 Ω
Thanks for that. I just noticed I made an error on 1 & 8. I missed AUTO and got my values out of sequence. FAN SPEED (using pins 1 (earth) and pin 8) AUTO 183.7k ohms OFF 66.0k ohms 1 15.5k ohms 2 7.44k ohms 3 2.475k ohms 4 1.2 ohms Looks like they are very close.
For future reference, to test the control panel fully (by itself), you would also need to measure the resistances between pin 3 (power) and pin 8 (output) at various fan speed settings. It looks like the control panel is a voltage divider circuit. You could also apply power to the panel on pin 3 (and earth) and check the output voltage on pin 8 (and earth). In the diagram below, the potentiometers represent the resistance networks (which are controlled by the fan speed knob). Using the resistance values measured, the voltage output can be estimated. Divide the resistance on pin 1 (and 8) by the total resistance of the two resistor networks to get the voltage output (as a percentage), then multiply that by the input test voltage on pin 3 (e.g. 12v). Smaller voltages can be used if 12 power supplies were not available. Image Unavailable, Please Login Purely theoretical, of course. Also, if the panel was hooked up to the HVAC ECU, the internal resistance of the HVAC ECU would have to be considered.
Oh, there goes my theory. This is at panel pin 8, not at the fan speed controller in the luggage compartment?
No at pin 8, you can try with your controller. Do you think Ferrari still has the circuit drawings for everything?
Indeed. I confirmed your findings with a small 9 volt torch battery. I get the same 2.7 volts at all settings. Maybe Miro has some ideas?
I believe that the selected resistances/voltages sent to the AC ECU by the switch on the Control Panel are one thing and that the voltages sent by the AC ECU to the Fan Controller are another. The AC ECU probably uses the inputs from the Control Panel switch just as basis to establish the voltages to go to the Fan Controller. For the 4 speeds set by the rotary switch, and assuming that they are evenly spread over the range, the Fan Controller should be getting approximately the following voltages from the AC ECU (based on my bench tests of the Fan Controller): 0 - 0 V 1 - 1.2 V 2 - 2.4 V 3 - 3.6 V 4 - 4.8 V (full speed)
This is clearly more complicated than I thought. The constant voltage output on pin 8 changes when I select RECIRC. But again, it's all the same voltage value (whatever the fan speed setting). It's interesting to see that the STOP and RECIRC buttons are illuminated (when pushed) with only power on pin 3 (plus an earth on pin 1). I think I was expecting the dimmer voltage on pin 2 to provide lighting for these switches.
I have ordered a new regulator unit, found an original one from Fiat. Just to be sure, i got constant 3.5V on pin 6 despite whatever the fan speed position is, are you sure this will change when i measure with the connector connected to the regulator? I really don't hope the ECU is the problem again as I already sent it for repair and they said the fan speed problem is not the ECU as they checked.....
Pin 5 of the Fan Controller provides feedback to the AC ECU. When this feedback is not available, it is possible that the ECU then sends a certain fixed default speed signal (fail-over) just to keep the blower running. At 3.5 volts, the blower would be running at ~75% speed.
Are you 100% sure about this? i thought pin 5 is for measuring the temp and only used when the fan speed is set to AUTO and will autoadjust the fan speed according to temp set at the control panel.
Pin 5 provides feedback to the AC ECU of the temperature of the power transistors inside the Fan Controller. There is an NTC resistor (sensor) imbedded in the cooling plate, between the two transistors. The purpose of this feedback is most likely to 1. Tell the ECU "I am alive" on start-up and 2. Tell the ECU "I am very hot (meaning ~130C), do something". Whether the ECU is programmed to do something, like switch the blower fan off until the transistors cool down or something else, I do not know. Otherwise, the automatic operation is based on the signals from the ambient temp sensors, external and internal.
Some time ago, I tested one of these Fiat 7710279 blower motor controllers and it would only start moving the motor from 6 bars selected on the fan speed display. It would increase the fan speed somewhat at the last 7 and 8 bars but it would not go to the full speed; nothing was happening at 1 to 5 bars. Is your Fiat controller running the blower starting from 1 bar? The one I tested looks like this: Image Unavailable, Please Login
