Hi there! recently bought a Ferrari 348 and I’ve just about cured every electrical issue, with the exception of the HVAC heater valve and flap. the issue I have - they both try and over rotate (I’ve disconnected them from anything to prevent damage) the valve works upon start up and does a minimal adjustment, but then if I drop the temp to ‘LO’ it rotates for longer than travel allows. Is this a potentiometer issue? Or an ECU/connection issue? (Possible broken wire between the pair I guess if I test the pot tomo and that seems ok) the flap upon start up wants to do atleast a 360degree circle, rather than the 90degree intended. any help much appreciated!! TIA
Would you clarify what you tried to say here. The hot water valve has 5 wires: Two for the motor and 3 for the 5.2k ohm potentiometer. How do you know what the flap (valve?) wants to do. There should be endstops on the valve assembly to stop it overrotating. I believe only half the pot is used (because of these physical limits), but that is to be confirmed.
Hi, yes- the hot water valve. Problem1 - the recirc flap. Problem 2 they both over rotate. I know because I’ve had to take apart from the actual plastic valve to stop the motor burning out (could hear it straining) the flap motor- is new as the old one had eaten the plastic gearing- presumably because it’s trying to over rotate. (Again havnt attached to flap until I cure problem) seemingly- the stepper motor functions correctly during small increments of temp. But when I rotate to ‘Lo’ it just spins for a time period then stops and error E5 comes.
It's the way it's designed. Some folks have installed limit switches, but it involves lots of fabrication/rewiring. Most folks just install a new recirc actuator and aftermarket brass drive and let it run for another 20 years. Not sure why the hot water valve is over-rotating other than what you have suggested (a potentiometer issue) or something wrong with the ECU. It's not actually a stepper motor, despite what the Ferrari documentation says. We've had 348 and 360 heater actuators apart, and both have ordinary motors. It was suggested that the 360* might be modified to fit to the earlier cars, but the valve seems to have different ranges (despite both using a 5.2k potentiometer). We can give you some potentiometer values for the normal range (if you need them). We're not 100% sure if the heater/hot water valve learns the positions on battery power-up like the air direction actuator. It may just use potentiometer values set in the ECU during manufacture. *The 360 actually has a failsafe mechanism which shuts off the electric motor at the endstops.
The motor/actuator for the valve has the Bosch part number 0 390 721 006. The Bosch 0 390 721 003 looks identical except for the output drive shaft which is shorter and has a cog on it. 006: Image Unavailable, Please Login 003: Image Unavailable, Please Login It seems possible to swap the endplate with the cogs on it with the Ferrari endplate with the long shaft on it (only 2 screws need to be removed) 003 endplate: Image Unavailable, Please Login There are possible issues with this, though: Gear ratios might not be the same Position calibration (internal potentiometer position vs transplanted shaft position) 003 actuator is just as rare as the 006 The original fault with the Ferrari part could be a broken plastic gear on the end of the shaft (inside).
On the Ferrari pump, the shaft of the 006 motor has been shortened (customised) and appears to be the same as long as the shaft on the 003 motor. One thing to verify is whether the shaft diameters of the 006 and 003 are the same. They probably are.
So it turns out, it was the potentiometer at fault. Replaced the valve and all is fine. just need to wire in limit switches for the flap. Presumably this flap works on some form of timer within the ecu. Poor design in terms of it not knowing its location. thanks for everyone’s help
Ran some voltage/movement tests on the -003. The valve has a 180 degree physical limit. The potentiometer is around 4.87k ohms. Image Unavailable, Please Login Fully clockwise (as viewed from the output shaft side of the actuator... see photo above), which I assume is fully open, the resistance between pins is: 2-3 = 235 ohms 3-4 = 4.72Kohms Fully anticlockwise, the resistance between pins is: 2-3 = 4.44kohms 3-4 = 0.512kohms Values for OEM -006 ( thanks to @darrenliu ) Potentiometer is 5.12kohms (400 ohms difference) Valve fully open (when fitted to car)... I assume fully clockwise : 2&3 - 2.720Kohms 3&4 - 2.681Kohms Valve full closed (when fitted to car).... I assume fully anticlockwise: pins 2&3 - 5.39Kohms 3&4 - 13ohms Even with the restrictions on the car, the OEM pot goes to a lower resistance value. I'm wondering if I reassembled the actuator properly. I may be a cog tooth out. 24 teeth per 360 degrees = 15 degrees per cog = 350 ohms per cog (approx) on the -003. This might be something for the too hard basket.
I presume you mean "the motor (003) has a 180 degree physical limit" (the valve has limits at 90 degrees). The heater valve and its motor, as modified and assembled for the 348, each have external limits to their rotation of about 90 degrees. The shaft of the Bosch 006 motor has been shortened and a steel bar has been attached to it. This bar hits the two metal stops on the metal bracket between the valve and the motor (or the motor actually does not hit the stops if the ends of its travel are controlled via the potentiometer; if this is the case, then the stops are just "plan B" if something goes wrong with the control). The "arm" that operates the valve is bent at 90 deg. at its end and attached to the side of the motor's bar with a nut. There are also two plastic stops for the valve "arm" on the plastic body of the valve at about 90 degrees. So, the shaft of the motor does not operate the valve directly but via a "coupling" formed between the motor's bar and the valve's arm. The very crude drawing below shows how Ferrari "married" the Bosch 006 motor with the Volkswagen water valve. Image Unavailable, Please Login The valve in closed position: Image Unavailable, Please Login VW valve before modification by Ferrari: Image Unavailable, Please Login
Some further info on the heater valve I found in my archives: The picture below shows the closed position of the valve to which I brought it on the bench using a battery. The valve itself (the white plastic seen inside the hose adaptor) fully closed just before the motor bar and the valve arm hit their respective stops (the motor bar was ~ 0.5 mm, and the valve arm ~1 mm, away from its stop). At this position, I measured 1 Kohm at the potentiometer pins as shown on the picture. Image Unavailable, Please Login Since the valve is positioned by the AC ECU at various degrees of opening based on the feedback from the potentiometer, I believe that the fully closed and fully open valve positions are also determined (and the motor stopped) by the AC ECU and not by the physical stops. Since the pot based control of the valve degree of opening is already there, it is easy to also include in the AC ECU lookup table: 1K=closed/stop. Running the valve motor up to its physical stops and stalling it would cause serious damage to the motor's reduction gears since this motor is considerably more powerful than the motor operating the recirculation flap. Image Unavailable, Please Login
So pins 3&4. That doesn't seem to match any of darrenliu's values. Having said that, we still have to determine if his valve is functioning properly.
yes Ian, Miro measured 1K between pins 3&4, and i measured 13 ohms. I think its possible that my pot is faulty, causing the motor to hit the extremes and stall, drawing more current. i measured 240 Milliamps when the motor was in stall. Do you think this much current would blow the op amp on the ECU (as in case of my HVAC ECU)? when the motor is free travelling (moving the valve), the current draw was 70 milliamps.
The recirculation flap actuator is just stalled at end positions and seems to remain stalled as long as the ignition is "on". It does not seem that there is any timer (or overcurrent sensing at stall) circuit in the AC ECU which would cut the power to the motor short time after it has been stalled at the flap fully closed or fully opened positions. I never had a working AC ECU in my 348 so I was unable to verify whether there is a timer or not and, as far as I know, nobody else has, so far, established that there is such timer or overcurrent cut-off function. In my 348, due to non-functional AC ECU, I wired a switch and added a small relay to operate the recirculation flap actuator. To prevent the motor being stalled at the flap end positions, I added two microswitches - attached them to the body of the heater box and added an "arm" to the actuator shaft to activate the micro switches, as shown on the pictures. I used thin aluminium sheet and made the arm like a fork so that I could "fine-tune", by bending the fork slightly, the point of switch-off of the motor when the flap fully closes (fine tuning of the switch-off at the flap open position was not necessary as it was not critical to set it at some precise position of the open flap, i.e. you can have some of +/- here without much effect on the fresh air flow). Image Unavailable, Please Login Image Unavailable, Please Login Added actuator Arm/Fork: Image Unavailable, Please Login Wiring of the Limit Switches: Image Unavailable, Please Login
