i thought it was stated in this thread somewhere. also any good electronics shop should be able to change out these chips. its very easy. i youtubed it and did it myself
Did some diagnosis yesterday, the 360 ECU definitely does not work with the 355 or there are some electric gremlins... The voltage 12v is coming from the ECU to the heater valve motor no problem, the valve moves when you apply voltage manually to it. I also tried to measure the potentionmeter of the heater valve motor, it reads 4,8K Ohm as it should, but then i tried to move the motor some steps and stop to measure and the resistance changed, but after a minute later the resistance changed again without moving the motor. What is going on here? potentiometer failing? it should read different constant resistances depending how much the motor has turned right? Anyone know the correct resistance for the different dial positions on the control panel that it sends back to the ECU?
The control panel pin assignments we know are: 1. Earth 2. Background lighting 3. Panel power in (12v) 4.??? 5. Temperature control output (4.9volts to 24mv) 6. STOP 7. ??? 8. RECIRC With panel powered up the voltage on pin 5 (Yellow) varies as the temperature control is rotated :- Min 4.95V 64F 4.62V 68F 3.61V 72F 2.58V 76F 1.57V 80F 0.63V Max 24mV
But the voltage from the ECU to the motor should be a constant 12V despite potentiometer setting right? The above values are those from the control panel to the ECU?
As far as I know, yes. Someone else measured them. Well, the motor changes direction, so +/-12 volts and reduces to zero volts a few seconds after the valve hits the endstops. The current in the circuit was reportedly like this: It seems odd, though. You would think that the ECU would know where the endstops are, not wait for the valve to hit them.
Yes that is the purpose of the potentiometer. The potentiometer receives a fixed voltage (most probably 5V) from the AC ECU across its end pins and sends back to the AC ECU a varied voltage (from its mid-pin) in the range of approx. 0.5 to 4.5 Volt, depending on the pot's position (i.e. the valve's degree of opening). By this voltage, the AC ECU "knows" the degree of opening of the valve and should also know when the valve is approaching fully open or fully closed position and should stop the motor before it hits the stop. However, if something goes wrong with the AC ECU's "lookup table" and it is unable to recognise the approach to the mechanical stops, the motor will hit them so, perhaps, the AC ECU has another "fail-over" protection circuit which cuts power to the motor if it gets stalled (starts drawing high current). This circuit would also protect the motor if the valve gets jammed. However, I do not know whether the mentioned protection circuit actually exists in the AC ECU.
The protection is possibly the failed amp IC chips . I mean it protected the car from burning.. I guess.
Might the system be auto-calibrating? I don't know the conditions under which the measurements were being done. If the system had recently been powered, could the ECU possibly have been determining the potentiometer resistance at the endstops?
The ECU logic includes reading and reacting to the outside air temp as read by the sensor on the mirror compared to the inside cabin temp read by the sensor on the left hand side of the dash.
Yup. Yea. I know....but thought I would toss that out there so folks know there is a lot of sensor reading / reacting that we really don't know how to measure. Hate to bring the car in for an SD computer read for the damn HVAC!
Anyone tried to get hold of the old circuit board schematics for these ECUs? Was it Delphi who aquired Motulo and is Delphi still alive or aquired also?
So this inspired me to finally dig into mine that has a control valve issue. Last fall I had pulled the motor off the valve to manually control the valve as needed for those last few drives before hibernation. At the time I spot checked the motor on the bench and chalked it up to ECU. I now have the the amp ICs shipping. However I figured I'd check the motor more thoroughly before fixing the ECU to possibly kill it again. What I've found is that my motor operates and the potentiometer works... however.. during operation cycle testing the motor at certain times of startup would draw high current and instantly smoke even. I can easily believe that a motor working like this would cause havoc at the ECU. I'm going to dig into the servo motor itself before I call it a loss as these seem hard to find even in substitute forms.
Confirmed the motor is shagged. Disassembled and found 2 components loose inside. This disk has detatched as well as another piece. I've cleaned it all out and reassembled and the motor is operational. I'm convinced this cheap motor self destruction likely takes the ecu with it. The motor was operational, but had some intermittent odd noises and high current immediate shorting. Well thats been found. Image Unavailable, Please Login Image Unavailable, Please Login
If that is in fact the case, then that is some shotty engineering in my view. ECU's generally operate a control circuit to ground a relay coil and let the relay handle the higher current to operate the motor. That design architecture keeps the ECU all low voltage between .5 to .7 Volts and thus protecting the ECU for higher current. Another measure (not sure if it would be cost prohibitive) is a thermal breaker built into any circuit that handles a load so that in an event of a short or high load, the breaker would just open instead of smoking the ECU. Maybe an EE on here can jump in?
I generally agree. I'm actually a retired EE, although I've forgotten more than I knew. As a whole I'm not entirely impressed with the entire suite of Bosch engine management, electrical systems, and harnesses. but stating that may be on the same level as bringing up politics and religion at a holiday dinner. May just be a sign of the times. Considering the usage and mileage, things seem to be on the "fragile" or Frageeelay side. You could argue that the ECU is really an integrated control module in this case... The failing IC's are amp drivers. That said yes shoddy design not having protection integrated to prevent failures.
The disk that detached is a varistor probably for electrical noise reduction in this case, maybe some surge suppression. The motor is functional without it, but it was there for a reason. I may try to source another motor or harvest one out of something that is still available. There are no worthwhile markings to cross reference a direct replacement from Johnson. This is likely used in a lot of applications though.
@Qavion You have the diagrams associated with P/N 63307100 Timing Actuator? I have the part out and would like to test it. Wires: Index hole Purple Green Yellow Black Red This is the actuator that moves the air diverter flap. Mine, as many here, is stuck on defrost. I did replace it many years ago, so think it is OK, but testing it's movement would be a logical next step. Image Unavailable, Please Login Image Unavailable, Please Login
This post might help: https://www.ferrarichat.com/forum/posts/146316299/ Red and black is the motor Yellow is power to the potentiometer Green is the potentiometer earth Purple is the potentiometer signal going to the ECU (i.e. the wiper arm) Full diagram here for the 5.2 https://www.dropbox.com/t/bbKPkYmZ4QV999j2
I'll see that amd raise you one. Lol Anyone have the heater valve potentiometer values at each end of the travel? Its possible to calibrate through a tiny hole. I actually did take measurements prior to disassembly but they are innacurate now after cleaning it all up.
