2001 Modena 360 Cruising along at 70-80 MPH for an extended drive, the oil temperature suddenly spiked from 180 °F to peg the gauge, causing the red light to come on. Before I could ease the gas, it settled down to about 230 °F then back down to 180 °F. All the while the water temperature was rock-solid at 180 °F and the oil pressure was 75 PSI. Ambient temperature was approximately 70 °F. My initial thought is that is a fluke (Right, just keep telling myself that. ) but I replaced the oil temperature sending unit because that was the first thing I thought of. Yesterday the oil temperature gauge was tracking the water temperature gauge fairly closely, as it should be. This was after a thirty minute highway drive home when it was 90-95 °F outside. This morning on cold start, the oil temperature moved off of zero sooner than before, again following the water temperature. At the end of the commute (same highway distance, but 75-80 °F outside) although the water temperature gauge was steady at 190 °F, the oil temperature flicked from 190 °F to 250 °F to 230 °F to 190 °F all in a matter of ten to fifteen seconds. Any clues as to what might be the culprit? At the bottom end of the wire under the car, it plugs directly into the temperature sending unit. At the top end of the wire behind the instrument cluster, does it also plug directly into the back of the gauge or is there some sort of “interface module” between the gauge and the wire connection? From the sending unit to the temperature gauge, is it a continuous run of wire or are there junction points to check for along the way? If so where and how many are there? Perhaps behind the seats or some sort of terminal strip in the footwell?
I realize that, but until I get my hands on the wiring diagram, my query is if anybody might suggest any specifics, as opposed to high-level commentary.
and I am no mechanic for sure...the first thing I would think about doing is changing the temperature sending unit. Those things don't cost too much and should be an easy job to do. And, since the sending units are known to fail it would be preventative maintenance if nothing else. I was having similar strange fluctuations in oil pressure in my 360. Changed the sending unit and the issue disappeared.
I did, as stated in the second paragraph of the opening post. My presumption is the wire from the oil sending unit is not a continuous path to the gauge in the instrument cluster. Knowing how Ferrari may have junction points, my question is if anybody knows about any inline connections in that wiring ... behind the seat, under the center console, above the footwell, etc.
Grounds (under engine cover on the frame and wire to engine on drivers side). Clean them... and then reseat the connector from the engine harness behind the drivers seat into the main wiring harness. Did you check for oil film in the coolant reservoir?
I had mine acting up a couple months back. I elected to replace it. http://www.ferrarichat.com/forum/360-430-sponsored-yellow-compass-group/520893-oil-temperature-sensor-104628-replacement.html
Is this a large braided cable from the engine block directly to the frame? Could you describe the location of the pin connection behind the seat, and-or the wire color? No oil film in the coolant reservoir and no frothy coolant in the oil de-aerator. Because the oil and coolant are not cross-mixing, and because sometimes the gauge needle twitches, that concludes in my mind it must be intermittent electrical.
Assuming I made no errors following the wiring diagram, the oil temperature sender is 25T and has one brown wire. The other side must be the engine block ground. From the sender, the brown wire goes to connector 26H/12H, pin #7. This connector pair is behind the driver seat next to the big + power post. There are three connectors in that location and this one is the top pair. From there, the wire goes to connector 25D/8D, pin #15. This connector pair is in the central tunnel, probably near the gear shifter. The wire terminates on the cluster 6E, pin #11.
+1. I had a similar issue with reading very hot suddenly on a previous 308GTS I owned...replacement of the sending unit fixed it right up, and was a simple DIY. Unless the sender is crazy money, I would replace it before I wasted too much time tracking down a bad connection, that may not exist. After all, a bad connection could cause a loss of signal...showing cold...but hot? Unlikely in my experience...but I'm no expert by any means.
my experience is a bad ground makes the temp guage read higher. make sure your engine ground strap connection is secure and clean
The first comment suggests a loose ground connection causes a cold (zero) reading and the second comment suggests a loose ground connection causes a hot (pegged) reading. I don’t know if the oil temperature sending unit is referenced to “positive” or “negative”. Depending on how that circuit is designed, an electrical open (loose ground connection) will cause the needle to swing one way and an electrical shunt (short) will cause the needle to swing the other way. make sure your engine ground strap connection is secure and clean The water temperature sending unit works on the same principle, that it needs to have a good engine-to-frame ground to complete the electrical circuit. My water temperature gauge works perfectly, which implies the main ground is good. By process of elimination, this implies the wire from the sending unit to the instrument cluster is the culprit. Although it requires more work because the undertray needs to be removed, my bet is to begin at the bottom of the car, to inspect the wire where it penetrates the bulkhead at the rear of the cabin. That is the low point, where rain splash (from highway speeds for example) might compromise the wire.
Unless the hot indication is random, and not the result of rising with engine use or time since it was started from cold, I would still believe a faulty sender is most likely the issue. But if you have the time, there is no reason not to eliminate other possibilities. The other possible issue is a bad oil cooler thermostat...or thermoswitch to the fan on the oil cooler (if a fan is present).
The temperature sending unit was replaced as the first step. On a 360 there is no fan on the oil cooler nor is there a thermostatically controlled bypass / mixing valve. Oil is forced directly into the cooler from the pump then gravity drains back to the pan. Apart from the cooler being a static component of the oil plumbing, there are no external influences (other than airflow, which is moot in this case) that affect oil temperature. There are only three culprits in this situation … sending unit (replaced), instrument cluster (not likely as everything else works fine), loose wire or ground. For those who have looked at a Modena wiring diagram, if I counted correctly there are seven-three different grounds in the various electrical circuits. But from what I can tell there are only two on the instruments circuit. One is behind the driver’s seat which is tight, and the other I have not gotten to yet because the undertray has to be removed. The only other possibility is abraded insulation on the wire from the sending unit, which should be an easy repair.
When I used to test jets prior to turning over to a customer often we would see issues with an installed wire harness before final button up. First order of business was to touch the whole thing and free up any strains and check it's clamping locations and bulkhead penetrations. If you have the time to trace the harness with your hands and wiggle it you may find someplace that lends itself to a break in continuity by being too tight or kinked or bunched up at a grommet where it passes through to the cabin or a junction box. Just a thought.
Here's my take on this... Perform a resistance measurement between the engine block and frame ground. You should see about 1-1.5 ohms. Anything higher, I would check for grounding issues between engine and frame ground. Depending on the quality of your VOM, you might need to zero out the meter or take the resistance of the test leads into consideration before making the actual measurement. It's possible that the gauge itself has an intermittent problem. It's also possible that the analog signal (variable voltage level) from the oil temp sensor is being re-translated by the smarts on the instrumentation cluster and driving the gauge using a pulse-width-modulation method instead. You can test the above by substituting the oil temp sensor with a 10K potentiometer using one of the outer and center connections of the potentiometer. With the ignition on/engine off, turning the pot CW/CCW will result in movement of the gauge needle. This will allow you to test the wiring to the gauge as well as the full mechanical range movement of the gauge.
I was seeing these symptoms last year on the oil pressure gauge. I tried cleaning the contacts on the sending unit and saw it stabilize for a while, but the problem came back. I ended up replacing the sending unit. I would not be surprised to learn that your sending unit may be faulty. Steve
He changed the sending unit per his post #1. OP - did you check the two connector pairs per my earlier description? Those should be relatively easy to get to. I would scrape the two corresponding pins clean and spray some contact cleaner on the female sides. Maybe scrape those too if you can. If you can access the sender again, I would just unplug the brown wire. If the instrument cluster gauge then pegs at max you'll know the wiring sense/design. And while you are there, check the brown wire connector for any sign oxidation or fraying.
Duh! I cannot believe I missed the part about him replacing the sender in his first post! Alright....slinking off to nearest corner...
I checked the connector pair behind the seat ... easy access. (Thank you for the wiring diagram!!!!) I did not feel like taking the tunnel apart to test the other connector pair. The ground bolt behind the seat on the driver's seat is tight. Next week I will have the car on a lift to clean the engine-to-frame ground and to inspect the brown wire from the sending unit to the rear cabin bulkhead penetration. To further exacerbate the sporadic nature of finding electric gremlins, the oil temperature gauge has been rock-steady for the past month. I drive the car two or three days a week. The fluctuating needle has done this only two or three times in the past fifteen months.
I am not familiar with a 360 but in regard to the sender, can you put the sensor in some water and heat it up slowly, use a kitchen digital thermometer and attach a meter to it, or does it need a 12 volt supply ?. Or you fit some wire extensions to the original connections and heat it in water. The water temp should register in the car and be the same as the water temperature. If that is the case it should prove the gauge and wiring- when it is hot you can jiggle the connectors about to see if the temp jumps about.
^^^^^^^^^^^^^^ Yes, they are being made different now or the markings are different than they used to be. I put some pictures in my thread of the markings and I think the ones that are readily available are of a different make and perhaps quality.
How many linear feet of wiring does a Ferrari have in it? What are the chances of finding this? What are the chances of it being located directly under a screw that holds the fuse cover in place which is behind the driver's seat? That may or may not be the problem (have not gone on the test drive yet) but it is testimony of how tedious chasing a wiring gremlin can be. Image Unavailable, Please Login
