I have some questions regarding exactly how the Mondial 3.2 heater controls, sensors and valves pumps are doing. For posterity having done some repair work on my heater system, I recap my understanding of the Mondial 3.2 heater operation, applicable to my 1988 model, with some questions littered throughout my summary. The Mondial 3.2 heater controls use a cabin air sensor (fed by a tiny suction fan), a heater box sensor and an evaporator sensor, along with the rheostat temperature control on the consol, all connected into a computer ecu. The system is activated when the console control push buttons are pushed, which will turn the fan on. The fan is always on, even at the lowest setting, once the pushbutton actuation of the system occurs. The ecu then controls provisioning a 12 volt supply, or zero volts, to the heater valve. 12 volt supply is always on when the climate controls are in their off positions, meaning the heater valve solenoid is energized to keep the heater valve plunger in an up position which in that position prevents coolant from circulating to the heater core. When the climate control is turned on (ie. the fan is activated), and the rheostat is positioned for heat, the ecu calls for heat, the solenoid is deenergized and the plunger defaults into its down rest position which is full heat. If the rheostat calls for cooling, the 12 volts would continue to supply the heater valve and it would remain in its up/no heat position, while allowing the ac compressor to kick in and offer the cooling effect. If less than full heat is called for the plunger cycles on and off as the ecu occilates the supply of the 12 volts to zero volts, and modulates the temperature of the cabin presumably to a set point defined by the cabin air sensor relative to the heater box sensor? If the heater valve solenoid fails, the plunger will be in the down position and the cabin will have full heat regardless of the rheostat setting. A small circulation pump in the engine bay area is also actuated when calling for heat, and only goes on if the controls call for actuation of the heater valve. There are three relays that are under the dash just above the console that appear to also be part of the system, one of which eg. triggers the ac compressor to turn on if the rheostat calls for cooling. Not clear what the other two relays are controlling, one would be the fan and the other the supply to the heater valve? Beyond the relays, my further question is as follows: If I put the rheostat control on the highest heat setting, what the does the computer tell the heater valve to do? Does it put out maximum heat, meaning the valve would be closed fully, or does the cabin temperature interact with it such that eg. if you put on full heat on a very hot day, would the units still call for max heat or does the cabin sensor affect how much heat is put out? If it is really cold, does the max heat setting put out more heat than if really hot outside? What are the cabin air and heater/evap box sensors actually instructing the ecu to do? If I removed eg. the cabin air sensor, or any of the other sensor connectors, how would the system respond in each case? The sensors can be tested for resistance as per the workshop manual as to whether they are functioning as intended, so the ecu must be a resistance recorder that interprets the sensors and acts in accordance with some programming. I presume this is a very rudimentary auto climate control system. (The wiring diagrams for my car are not so easy to read, so forgive my questions regarding the relays.)
I think your best F reference would be Chapter H of the TR WSM. TR don't have the auxiliary hot water pump, but the rest of it is very similar (if not identical). Not sure it will answer all of your detailed questions, but I think it's all there is. Only thing in your post that I don't agree with is the direction that the plunger moves inside the hot water valve to be energized/closed or unenergized/open: When the key is "off", or the key is "on" with a pushbutton pressed and the HVAC ECU wants heat = 0V applied to the two terminals of the hot water valve = the hot water valve piston is in the up position = valve open When the key is "on" and a pushbutton is not pressed (or a pushbutton is pressed, but the HVAC ECU does not want heat) = 12V applied to the two terminals of the hot water valve = the hot water valve piston moves down = valve closed. See the drawing of the hot water valve in Fig 18 on page H28 of the TR WSM.
The "A/C" relay actually provides constant power to the ECU's AC section when "ON" is pressed. There is a micro-relay inside the ECU that triggers the clutch when necessary, using power provided by the "AC" relay. The "heater" relay provides a ground to the heater valve when the system is "OFF", incl. with the ignition is on. This leaves the heater valve open when the car is "powerless", for example during filling of the coolant, allowing the heater to be filled and bled during production or servicing. When you press "ON" that ground is broken and the heater system power transistor inside the ECU provides a ground when the AC is active, and breaks that negative when heating is required. When the fan speed knob is turned to its full position it activates a microswitch.You can hear this. This microswitch bypasses the power transistor that controls fan speeds below that threshold and activates the "fan" relay providing full power supply to the fan. By the way, the rheostat doesn't control the cooling or heating directly. It serves as the input signal of your desired cabin temp and the ecu compares that to the measured temp (suction fan input) and the bleed air temp (inside the HVAC). The ecu then decides if cooling, heating or nothing (your wish is corresponding the the measured temp) is needed. The larger the measured difference of the cabin temp to your desired temp is the longer the ecu will activate either the heater or the ac via pulses (cycling of the AC clutch or heater valve, since they are on/off systems). If the temp cannot be reached, either will stay on permanently. In case of the AC, this might lead to evaporator freezing, especially if the fan speed is low - that's why there is a sensor there that will cut the clutch if the evap temp drops near freezing level - protecting the AC system from over-pressure (additional the hi-lo pres switch at the dryer, which is an emergency system). The evaporator freezing issue is also the main reason for the fan to run permanently at its lowest level when ON is pressed. The secondary reason is to pressurize the cabin enough to avoid any exhaust gas to enter via the outlets, especially when backing up. There is also a little "leak" tab on the fresh air flap of the AC which lets a minimum quantity of fresh air enter the cabin even when you press AC (aria circulata = air recirculation). AE mean aria esterna, external/fresh air. So, pressing AC doesn't activate the AC - it closes the fresh air flap, while AE lets fresh air enter the cabin.
That is an AMAZING explanation! Clever system. Should prove invaluable for posterity for others who need to sort out this system. I was always unsure why there was always a low fan speed on when the system was activated, and that explains the related evaporator sensor (which I actually can't see how one would get at that one under the dash if it ever needed replacing). Seems to be a reliable system but for the heater valve that has to have the small thin rubber plunger valve seat and bellows withstand the ongoing coolant immersion. Not sure I have ever heard an FChatter have an ECU fail, but maybe as age marches on that will change. I wonder if that Bosch ECU was proprietary to Ferrari or was also used on the Mercedes and later Bentley's that seem to use a similar heater valve. Would be interesting to know what the actual temperature and differential maps are that are programmed into the ECU. Having fully sorted my system, after isolating the problem to a weakened spring in the heater valve plunger, I went deep into testing and diagnosing everything, but not fully appreciating how it all functioned. So thank you for completing the knowledge base on this, sometimes fixing things but not fully understanding exactly what one fixed is less satisfying than knowing exactly how things are supposed to work.
When you remove the rain protection under the windshield wiper grill, you can sort of see/access it but it's not really removable without taking the dash out and dismantling the HVAC unit. You could sort of just stick a new on into the unit somewhere nearby... I had the micro relay inside the ecu fail and replaced it. I also unloaded the ecu on my car by adding a dedicated relay for the ac clutch in the engine bay, which draws 12V from the starter motor supply. So effectively, my ecu just commands a dedicated relay, reducing the load inside to "electronic" levels. I think "our" ecu is basically the same hardware as used on other cars but programmed for Ferrari - the response curves to achieve the desired temp change gradients vs outside temperature are linked to the output of the ac and heater system and the cabin air volume. The workshop manual shows the principle of the heater valve regulation; the AC clutch is probably similar: Image Unavailable, Please Login
1988 Mondial 3.2 - As for the two heat/ac Italmec relays under the dash area Ferrari Part number 110356 that are no longer available, I have determined the Bosch replacement that was OEM after the Itlamec was extinguished to be Ferrari part number 4013007, and Bosch part number 0 986 AHO 251. This was and is used on some other Euro cars like Jaguar and Mercedes so the stock should be around for a while. But those Mondial 3.2 owners might want to buy the spares while they are still available. The third single relay F part 110355 updated Bosch equivalent part is the same purple current Bosch one that would be used when updating our fuse box relays, that would beFerrari F part 40130106 and Bosch part o 332 209 151. Image Unavailable, Please Login
Correction: The purple Bosch relay 0 332 209 151 (old Ferrari pn 110355 and new Ferrari pn 40130106) is not in fact the correct part. This is despite it being on all the various part suppliers exploded parts diagrams, so if you order one from them you will not get the correct relay. The original Italmec relay does not have the centre pin. The only marking reference on the Itlamec relay is "12v - 056" . The hunt continues for the correct new Bosch equivalent. Or could one just chop off the center pin on the Bosch one? This relay actuates the heater valve. Image Unavailable, Please Login Image Unavailable, Please Login
The purple relay might be OK to use if you move a wire in the relay socket. I think I can see in the photo that the missing center terminal on the Italmec is labeled "87", but can't see the label for the bottom horizontal terminal. If it is labeled "87a", then by moving the wire in the relay socket normally going to this 87a terminal on the Italmec relay to the center position in the relay socket so that it connects to the 87a terminal on the purple relay = should work OK. If that bottom horizontal terminal on the Italmec is another "87" terminal, then, yes, you could just cut off the center terminal of the purple relay (or even just leave it there if there is no wire in the center position of the relay socket for it to touch). Please advise how that bottom horizontal terminal is labeled. PS They did the same thing on late TR where the HVAC relay that closes the hot water valve when the AC is "off" has no center terminal and has an 87a terminal in that bottom horizontal position. Maybe they thought that they were saving a few lira, but using a single special oddball relay rather than another purple one (that is used in a lot of other places) was a long-term mistake IMO. My guess is that the vendor making the HVAC system made this design decision to use an uncommon relay (and the Ferrari engineers would've used a purple-style relay if it was their decision).
There is no 87a on the Italmec. The top vertical pin is 30, left vertical 85, right vertical 86, and the middle and bottom horizontals are both 87. Would this Bosch item be the correct replacement? 0 332 119 166 (Their drawing is upside down from my Italmec pictured one) It is normal open, with no diode or resistor. Image Unavailable, Please Login
Yes, it would, but I'm not sure that I would trust that Italmec terminal labeling (knowing how the hot water valve works and what's shown on the euro 3.2 Mondial schematic where the relay controlling the hot water valve uses an 87a terminal and does not use the 87 terminal). My suggestion would be to measure the resistance between terminal 30 and that bottom terminal 87 on the Italmec with the relay unenergized and energized. The way the hot water valve works is: With the relay unenergized = terminal 30 should be connected to that bottom horizontal terminal (i.e., 0 Ohms or just a few Ohms) = closes the hot water valve. With the relay energized = terminal 30 is not connected to that bottom horizontal terminal (i.e., infinite Ohms) = leaves the hot water valve under control by the HVAC ECU. If the Italmec relay works in the opposite way = then that Bosch 0 332 119 166 would be the same. Does the relay socket not have an open unused slot in the center position? I.e., Does it have to be a 4-pin relay? If it does have an open center slot (and you do need the function of an 87 terminal in the bottom horizontal terminal), you could use the more common Bosch relay with two 87 terminals or even the purple relay as that also has an 87 terminal in the bottom horizontal position.
There is no wire for the centre relay pin in the connector. The Italmec relay when unenergized, terminal 30 to 87 reads 0 Ohms. When energized, reads infinite. I presume this means it is a normal closed relay. The Bosch purple relay, is the opposite. ie. Inifinte when unenergized, and zero when energized. The purple Bosch relay does not function in my car. It is a changeover relay, but because I have no 87a pin connector, it is functioning as a normal open relay. If the Italmec is a normal closed rather than a normal open type, the 166 Bosch part would not be correct. Based on the heater valve being always energized to stop the heat flow, and deenergized to cause heat, it makes sense the normal closed is the correct part for this application? I presume there is no diode or resistor in the Italmec relay?
What year is your car, as based on my preceding post, as there is no centre pin connector wire, removing the relay centre pin would have no effect? My car is the 1988 Mondial 3.2 Cab, CH88 version.
The purple relay will function as a normally closed (when unenergized) relay IF you move the wire in the relay socket from the bottom horizontal position to the center position -- i.e., move it to the 87a terminal of the purple relay. I'll give Italmec a big "that's a bad, bad thing to do" to use a relay base that mislabels the functions of the terminals.
Got it, I appreciate I am learning about relays as I go through all this. I get that the wire being moved to the 87a pin on the purple Bosch replacement will make the relay function like a Normal Closed relay. There is no direct replacement NC relay I have been able to find that would be "plug and play" in the existing relay socket and wire set up. Very odd they did that, must have been some leftover tractor relays that the factory acquired a big batch of.
I think it's more a case of an Engineer at the HVAC company picked an unusual, and little used, relay configuration from the relay manufacturer's list of possible relays -- disregarding what are the popular relay configurations. In theory, that Italmec relay will be less expensive than the purple relay because the Italmec relay only has one set of contacts inside; whereas, the purple relay has two sets of contacts inside. However, a special configuration, although possible and maybe cheaper, is always a hassle, and the relay industry virtually standardized on either relays with two 87 terminals or relays with one 87 terminal at the bottom and one 87a terminal in the center for everything. Doesn't surprise me that you can't find a relay exactly like that Italmec -- the demand for such a relay is so low that it would have to be special ordered (in a big run from the relay manufacturer).
1983 RHD quattrovalvole - this setup works. The heater valve socket on mine was marked with a red paint dot to identify during production where the "other" relay type goes. Image Unavailable, Please Login Image Unavailable, Please Login
So you must have moved the brown/white wire into the centre part of the socket? In my case the wire would be in the empty spot just above in your picture. With that change, I can see how the Bosch purple would function properly.. I know the move the wire trick now, it was still interesting to try to find a plug and play to make this relay replacement a more straighforward one for future owners. Add this relay replacement quirk to the little bag of tricks in unraveling the secrets of this car.
Yes I did - I think that's a pretty easy way to use a readily available relay and fully reversible for originality purposes if required. But it's not plug'n'play... sorry, I don't have a solution for that.
