Thank you all. Interesting that it has two thermoswitchs. One thing that I have started thinking about is that if you are standing still with the car or run below "running speed". and then accellerate up to 70 kph, the temp gauge goes down in a matter of seconds... On my car, the temp start to drop after only 5-10 seconds... I am thinking that the cooler temp reading is because the car moves faster forward and that cools the radiator by the wind that the car is running through (and that is probably right). However, how is it possible that it takes less than 10 seconds for the temp to fall when the temp sensors are positioned at the water "manifolds" right before the thermostat? It it really so that the water move so fast that the wind first cooled the water, and then the colder water went through the complete engine...? Sounds strange to me. OR it might happen that the water inside of the radiator was already quite cold and went through the engine.. But then the thermostat can not be open and make the water circulate through the radiator (but it should do as the temp is already very high (at 120 deg C). I did som hard driving today, and it seems like the catalyzers really heat up and the car could stand still idling with both fans on and were struggling to keep it under 115-120 deg. So I put on the heater inside the car at max, and then the temp dropped. I later turned off the engine, and put on the ignition (without starting the car) and let the heater run at full speed. The strange thing is that the heater blew really hot air for a looong time, like two minues. On other cars, the heat usually change to more like outsid etemp in only a few seconds. It felt almost like the water were circulating as the air that came out was warm for a long time. Any info on this? Does it have a circulation pump in the heater or in the engine compartment??!!!?? Thank you again.
Two minutes is not such a long time. There is enough (very) hot water in the heater for that. As to the water temperature dropping 10 seconds after you start moving, that is what I'm seeing with my car in hot summer days. I used to get water temperatures of 110C sitting in traffic at 35C ambient. Then I reduced the antifreeze concentration to 30% (I use Glycoshell, and Shell states that it's safe to go down to 25%) and, probably more important, I cleaned the space between the water radiator and the AC condenser. There was an incredible amount of rubbish in there, blocking airflow. Now in the same conditions the temperature goes up to about 100C. There is still room for improvement, I'm sure taking the radiator out and cleaning it properly would make a difference. Stefano
Hi everyone. Yoday I got the car back from the workshop with new water temp sensors for the fan ECU. The ca stays at 90-95 degrees C in all driving conditions except for highway driving when it drops to about 70. GOOD TO KNOW..: Normally, cars have a temp sensor inside the radiator which SWITCH on the (close the circuit) power to the relays which in its turn switch on the cooling fans. But on the 550 (I suppose also 456 and 575), the TWO sensors are more of a variable ohm design which tells the cooling fan ECU the different temperatures which is constantly changing, and the ECU will then in its turn determine when to switch on the fans. My fans were coming on but at different temps and at a higher and higher temp before it in the end was very hot. So am answer to all you who see high temps, it is not like you have to have a clogged radiator. It can in fact be as simple as the temp sensons for the fan ECU give "false" readings and the fans are not coming on at the right time. FYI!!
One of the sensors is a back-up if the other one does not turn on the fans. The primary comes on at a lower temperature than the back-up.
Taz, as the part numbers are the same, it is more likely that it is the same variable resistance sensor giving a continious variable (with the temp) signal to the fan ECU. Eurospares said the left side sensor gives input to this ecu, and the right side send signals to the Motornic ECU and if it sences a temp of 105 deg Celcius or more, the Motornic ECU oversteer the fan ECU to blow anyway. The right sensor is for monitoring the engine's heat (for mixture purposes). The third is for the gauge on the instrument panel. So the two sensors ar no on or off at 95 and 105 degrees.
Taz is right, both sensors are used only for the fans. They are identical, the ECU takes decisions, not the sensors. The latter only give a temperature signal to the ECU. When one sensor detects 95C the ECU turns the fans on. If this fails and the other sensor detects 105C the ECU turns on the fans. Stefano
456M- Things are not always complicated. If you read the WSM, it explains very simply how most systems on the 550 work. If you want more detail, it is handy to have a 575M WSM. Even if many details differ, the photos are worthwhile and many components are similar or identical. Ricambi sells them for $125 last time I checked.
On my car the temp was always a bit high before the fans came on. During this fall, the temp got higher and higher... My point here is that these sensors most probably will gradually start to give a false temp signal, and that these temp sensors should be replaced every 10 years or so to prevent the engine to run at wrong temperatures. I bought mine from Superformance in the UK and they were very cheap!
I agree! I forgot to ask the workshop to replace the temp sensors last year when my car underwent a major service, which included replacement of a couple of hoses under the plenum. So now I have 14 year old sensors in there, a bit worrying.... Stefano
My 550's cooling fan stays on after the ignition is turned off and runs until the battery is gone. Would this be a symptom of this sensor going/gone bad?
As Taz said..... that or possibly one or several of the relays that control the fans have stuck in their energised position, or the signals that control the relays are still coming in when they're not supposed to (car off). Do one or both fans run all the time? They don't cycle or shutoff? If so, that's a good sign of one or more relays with welded contacts. The A/C ECU is supposed to control the fans according to the signal from the thermistor in the left water manifold. These would be relays 5 & 6 in the schematic below, and H & R in the table. If that circuit fails, then the main Motronic ECU will turn on an Emergency Fan Relay (#7 in the schematic, and Relay "A" in the table), if the thermistor in the right water manifold goes above 221 degrees. If both fans are running after the car shuts off, I'd be suspicious of that Emergency Fan Relay, or if only one is running, I'd look at the relay that controls it. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
John, Did you notice in the diagram "Relays" we have 2 left fuel pump relays and 2 right fuel pump relays? Any idea why or how that works? I got fooled once. Left went dead and I instantly started looking at fuel pumps. I stopped when I saw left fuel pump. I did not read further until my next step in diagnosis passed which puzzled me so I went back to the fusebox. It pays to read.
Carl, yea I'd noticed that once before. Further, if you look at the stick on label that serves as the relay location "key", one set of those relays is referred to as "Left (or Right) Fuel Pump Signal" and the other set are called "Left (or Right) Fuel Pump". So what's the significance of the "Signal" wording? My conclusion, which is total conjecture , is that one relay per pump serves as a "starting" or purge relay, and the other one is for normal running. When you turn the key on, you'll hear both pumps run for about 2 seconds to prime/purge the system. These are one-shots, ie if you don't start the engine then, but turn the key off and then turn it back on, the pumps won't repeat the 2 second prime/purge. Only if you actually start & run the engine will it do the prime/purge the next time. I think these might be the "signal" relays. That's one theory. The other one is that Ferrari/Motronic have one relay in there to run the pump on a reduced voltage circuit, and the other one is for full voltage. This would have been a great idea to keep the pumps from recirculating hot fuel at idle & cruise, but I don't really buy that. It's interesting that both relays are joined somewhere downstream before the hot leads get to the pumps. One of these days I'll trace the circuits and try to figure out what they're doing. p.s. I also don't get the Gearbox ECU or Reverse Control relays, but haven't had any issues with them that I'm aware of, so haven't traced them out yet either.
That is another mystery. I never bothered to find out what reverse control relay is. I pulled that relay to run my dead LH fuel pump. I have not got around to replacing the relay I stole from the Reverse control. So far I have not found a use for it and just figure I run a list of electronic stuff I need and when I get enough I place an order. I hate just sending for 1 thing unless it is a must have.
John. FBB- One may turn on the back-up lights when in reverse. Does the 550 have a reverse chime like the 575M?
