355 Heater valve stepper motor testing.

Hello all
Does anyone know how to bench test the heater valve stepper motor.
I have Ian's wiring diagram but my valve wiring shows a white wire instead of red along with the others that seem to resemble the digram. I'm sure it's only +12 and reverse polarity but some guidance and how too's would be great.

 

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So a white wire replaces the RB (Red-white) wire on your car, Paul?

I'm sure Miro can answer this one I don't know if the stepper motor relies on reversing the polarity or if the valve is spring-loaded closed (and the output of the HVAC ECU fights the spring). Because it is a stepper motor, the voltage sent to the valve is a pulsed signal (a square wave with variable on/off times).

The potentiometer side of the circuit will be easy to check if you can get the valve to move through its full range. Power goes in on G (yellow), output on L (blue) and earth on N (black), although you could just measure the resistances on the 3 wires.

 

Mine has this plug configuration
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Apparently if it's doesn't work it just goes to full hot so stuck in the open position allowing water to flow continuously. Sounds like you need special equipment to test this motor

 

It's a bit hard to see the colours... Are they
white (formerly red-white)
black
blue
yellow
yellow-black

from top to bottom.

Or are the yellow and yellow-black reversed?

By not working, do you mean if it loses power it goes to full open?

 

Yes if it loses power. Goes to open. I will double check the plug tonight for exact wire colours. I'm pretty sure it's yellow/black then yellow, blue ,black , White

 

Confusing. If it moves to open without power, then it must be spring-loaded open. However, if you hit the STOP button on the aircon panel it is commanded closed. Does this mean that the power from the ECU needs to be constantly applied to keep it closed?

 

I have just sent the ecu to have the ic's changed. The ecu is none to stop suppling power to things. I had the chips and just thought get them changed. I have noticed a couple of weird things going on and want to test the HVAC electric motors so I know everything is working correctly. It's a poorly designed system that's for sure.

 

I should have said check the resistances on the valve plug pins (with the plug disconnected), but that would involve driving the motor artificially.

 

It is not a stepper motor but just an ordinary motor and its direction of rotation is changed by reversing the polarity of power (12V) supply which comes through the end pins (red lines on the pic) of the motor connector. The potentiometr rotates together with the shaft that rotates the valve and provides info on the valve position to the AC ECU to know when to stop (20, 50, 80 etc. % of opening).

You can bench test the motor by connecting 12V supply (needs just about 100 mA) to the end pins of the connector in one and opposite orientations. The valve will rotate towards opening and towards closing. Be careful not to touch any of the 3 inner pins with the power supply to avoid risk of damaging the potentiometer. There are stops for the shaft rotation near fully closed and fully open. Avoid running the motor until hitting the stops (stall the motor) but disconnect the supply a few mm before to stops.

If you also wish to test the potentiometer, you need to connect an ohmmeter (analogue, not digital) to the middle and one of the neighbouring pins (the blue lines on the pic). Then operate the motor in one direction and the other and see whether the Ohm change is smooth or whether there are any jumps of the ohmmeter needle, to open circuit and back to resistance.

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You are a champion. Thanks mate

 

It's working fine. Very happy with that.

 

Strange, the WSM says:

The water flow in the heater is therefore regulated by the ECU with an impulse cycle of variable length and frequency, moving the valve in the position which is required and detected by the ECU by means of a 4.7 kohm potentiometer internal to the motor.

There is something similar in the 348 WSM, too.

 

Sometimes I don't like that WSM hahahaha witchcraft and snake oil spoken in those I think.

 

Can a bench test be done on the inside cabin rotation/vent direction motor? I think it has 4/5 wires

Can a bench test be done on the in cabin vent direction/flap motor in the same way? 5 pin round plug

 

Yes, it can. This is for the actuator on 348, most likely same on the 355 and with same wire colours. It will change the direction of rotation according to the polarity of supply (12V) on the "motor" pins. Again, the ohmmeter goes between the "mid pin" and one of the "end pins".
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I guess part of the description is a puzzling due to translation Italian to English. It probably means:

"impulse cycle of variable length" - the ECU switches the motor on for a period of time, longer or shorter depending on what valve position is to be reached.

"impulse cycle of variable frequency" - how often the ECU switches the motor on and of, in one or the other direction, to fine tune the valve position; I would take the "frequency" to mean how many times (on-off, cw-ccw), not to mean frequency of a PWM signal.

 

Anyone tried this alternative part?
Part No: 63306400/A

https://www.ferrariparts.co.uk/part/ferrari/63306400

Less than half the original cost.

I've seen some selling the motor alone for that price (and it still has to have the shaft shortened to fit)

 

You would just need to confirm the No on the Bosch motor on that unit
(0390721006) I have tried recently to acquire one. Most places are out of stock even the Saab equivalent is unavailable. That price is about right with the exchange rate still be around the$800 AUD

 

According to FChat, the part number is insufficient for identifying the correct motor. There are sub-types with different case stampings.

 

Doesn't suprise me. Unless someone with stock actually checked/confirm the No it could be hit and miss. I tried every Saab dealer and wrecker in Aus. With no luck new or 2nd hand. Luckily enough mines fine after testing. All motors actually so I suspect the ecu is the culprit. I will know next week when it gets back from chip change.

 

TUV regulations require a default of hot air and defroster on when there is a system failure. So any time the heater valve control loses signal it will open the valve.

 

More food for thought... A gentleman on another Ferrari forum has just provided some feedback, today, on the hot water valve.

If power is removed from the valve when it reaches the fully closed endstop, then won't it spring back open?

 

The ecu knows when it's getting close to either end stop due to the potentimeter inside the unit(my observation shows the ohms dropping or rising pending direction). I'd say by the torque application through the motor and gearbox it would need to be a pretty hefty spring to open or close the valve.

 

Assuming the pins are numbered consecutively 1, 2, 3, 4, 5, with an ohm meter set to the 10k ohm scale, connect one lead of the ohm meter to pin 2 and one to pin 4. The resistance should be around 5k ohms. Then connect one lead to the center pin (3) and the other to either pin 2 or 4. You should see a resistance somewhere between 0 and 5k ohms. Now, with a 12 V source, connect on side of the 12 V to pin 1 and the other to pin 5. The motor will move as long as it is not against a stop. The resistance should change as the motor moves. Run the motor all the way to a stop. Then reverse the voltage. The motor should reverse. If one of the leads of the ohm meter was connected to pin2, move it to pin 4, or vice versa and repeat the application of voltage again and monitor the resistance. If the motor moves and the resistance varies between 0 and 5k ohms (approximately) in both directions everything is ok with the motor.

 

If you're having a problem, don't just check at the connector. Mine in the 348 was malfunctioning because the signal from the potentiometer wasn't working. I took the whole thing apart and found that there was a break on the circuit board between the potentiometer and the connector. There was no visible crack, but it showed up when I put a continuity tester on it. I took the board to an electronics repair place and had them solder a bridge wire in for me (my solder beads end up looking like metallic tumors). It solved the problem I was having with the heater throwing an error code (E5 or E6 I think, I've forgotten) and shutting off all heat.

Here are before and after photos.