Testarossa was not starting. Engine cranked but With Steve's help I was able to figure out the problem. The culprit was the black flywheel TDC SEN8 sensor. It measured 2MOhms instead of ~700 Ohms. Ordered one from F-Quebec in Montreal and installed it yesterday. The car started right away. Thanks Steve for your helpful posts, pictures and PMs. While getting the car ready for a drive I noticed that both the main temperature gauge and the oil temperature gauge are not working. They do not seem to register at all. It is possible I may have done something to them during the earlier diagnosis as I pulled out many connectors and reseated them. The C11 (9pin) connector is intact and so are the various other ones - I double, triple checked them. There is not much on the forum on this topic of temperature gauges not working. Any ideas where I should look to troubleshoot?
Because it is very improbable to have only those two gauges not working at the same time Seriously, the electrical paths for the sending units for those two gauges are completely independent, and if the (common) +12V power was lost, there should be more gauges not working. Are you saying that only those two gauges aren't working, but the oil pressure gauge and fuel level gauge are working OK?
Steve, Yes. Only the two temperature gauges are not working. The oil pressure gauge and the fuel level gauge are fine. Is it possible I may have disengaged a thermistor somewhere?
It would have to be "disengaged TWO thermistors" as they don't share any common connector. The water temp thermistor is at the back end of the water Y-pipe on the top front of the engine; the oil temp thermistor is at the bottom of the oil tank.
I am wondering if there is a common electrical connection for the two temperature gauges as I never went anywhere near the oil temp thermistor. I did play around with the water y-pipe to measure 12V.
Not in a way that would affect those two gauges, but not the other gauges nearby (i.e., a common +12V and ground is supplied to the oil pressure gauge and the oil temperature gauge; and likewise, the common +12V and ground is supplied to the oil temperature gauge and fuel level gauge).
Beats me. The car starts now and runs well but the temperature gauges never register anything. I don't feel comfortable driving the car not knowing if it might overheat. I will go through all the fuses again tomorrow and will reseat the relays and connectors - but this is just another iteration of what I already did today. Let me know if you think of some tests I can do? Thanks
I started looking at the Testarossa Workshop Manual online to see if I could trace the problem on the schematic but have run into a roadblock. 1. The manual points out the main temperature gauge (H2O temperature gauge) as #46. 2. The Engine Oil temperature gauge as #61 3. The Oil thermometer control thermometer (oil thermistor) as #106 4. The H2O Thermistor as #116 I can't find 61, 106 and 116 on the schematic. Does anyone have a better schematic? I need to find the right terminations to check the trace with the multimeter. Has anybody got any experience with this? Have attached the schematics. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Go to All Ferraris Under "Other Manuals", download either of the TR wiring diagrams (Fig 7 in either IIRC). They are maybe for little bit newer TRs, but, for this temperature stuff, they are all the same (e.g., the "106" got truncated to "10nothing" in the official printed TR WSM so that's why you can't find 106 in that horrible scanned copy).
Isnt that where the temp sensors are located? Go back and re-seat, verify the brown Bosch connector is(?) is connected properly.
Thanks for the lead Steve. These schematics are much clearer. Chris, you mention to "verify the brown Bosch connector is(?) is connected properly". Where is it?
Traced the H2O temp gauge connection to C11 (pin 7, grey wire). It measures +7V when the engine is running. I am not sure if its supposed to be +12V as +7V sounds like an odd reading. It is terminating at connector C6 (under the passenger footwell). The grey wire is buried but I will get to it to take a measurement. This is a real gremlin. I am surprised that nobody has experienced it yet.
Getting a non-zero voltage there is a good thing (confirming some power is reaching the gauge), but the easiest first diagnostic step is to just unplug the grey wire from the water thermistor and touch it to ground (like the Y-pipe casting) with the key "on": If the water temp gauge goes to maximum = that's what it should do (and suspicion would shift to the thermistor) If the water temp gauge stays dead = got to be something in the gauge or the gauge wiring IIRC, there is a ground wire connection to the Y-pipe -- you didn't remove that did you?
Steve, you wouldn't happen to have a picture of the y-pipe with the ground wire connection handy? I just want to make sure I am looking in the right spot.
In the below thread go to post #3. Steve has a picture with a red arrow. Just to the right and slightly above the arrow you will see a brown and black connectors. correct me If im wrong but dont these sent temp info to the cockpit? http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/194997-testarossa-no-start.html
No, the black one is a 2-channel thermistor that sends water temperature information to the two KE-Jet injection ECUs, and the brown one is the thermo-time switch. Only the 1-channel thermistor (with the single grey wire) at the back end of the Y-pipe is involved with the water temp gauge operation in the cockpit. Image Unavailable, Please Login
It's the wire terminal mounted on the stud (and nut) on the RH side of the Y-pipe pointing towards the AC compressor -- but after thinking about it more, if it wasn't connected, that would mess up the operation of the "black" 2-channel thermistor for the injection system that Christian mentioned (so, since you say the engine is running well, all that must be OK). Try that simple diagnostic test... Image Unavailable, Please Login
The ground connection is fine. The diagnostic test you mentioned is difficult to do because I cannot access the grey wire connector on the Y-pipe without removing the fuel injectors (carbs?). Even if i could get to it I noticed that it has been sealed with silicon caulking (i wonder who did that - its got a gob of silicon on it?). There has to be a common circuit for the water temp gauge and the oil temp gauge as they are both not working. I am at a loss.
Let us know when you find one that wouldn't affect the other gauges too Yes, that's not a good sign. You wouldn't have to unplug the wire - if you just touched a grounded metal probe to the metal of the plugged-in wire terminal or the spade terminal on the sensor with the wire still connected, that would work too, but if it's coated in RTV, you'll need a very sharp "pointy" probe to penetrate the RTV and contact the metal.
Steve, I will do the the diagnostic you mentioned but in the meantime if you look at the attached schematic you will see the oil thermistor terminates at the C3 connector (brown wire) behind the vertical console where the oil temp gauge is mounted. Since i have the vertical console undone and have access to the C3 connector, I measured the operating voltage at C3 on the brown wire. With the engine running it starts at +7.6V and as the engine warms up it gradually drops to +6.8V, however the needle on the temp gauge does not budge nor needle on the engine temp gauge. I don't know the relationship of the voltage to the temperature for this transducer but there must be some correlation. It beats me as to why the temp gauges are not registering anything but the fuel gauge and oil pressure gauge are fine? Image Unavailable, Please Login
I can't recall anyone posting voltage on the thermistor wire vs gauge needle reading, but you can do the same sort of diagnostic test with the oil temperature system -- just touch a jumper wire to ground that brown wire pin (while it is still connected) in the C3 connector with the key "on"= oil temp gauge should go to maximum temp. You can also confirm/deny if 12V power is reaching the gauge by measure the voltage between the N (black) ground wire pin 2 and the VB (green-white) wire pin 7 in that same C3 connector = should be 12V.
1. Measured the voltage between the N (black) ground wire pin 2 and the VB (green-white) wire pin 7 at C3 connector. It is about 11.5V. 2. I put a jumper wire to ground the brown wire pin (while it is still connected) in the C3 connector with the key "on". The needle does not move. The measured resistance between ground and brown wire is only 56 OHMS. Is something shorting out the gauges to ground?
That's good (and not surprising since you report that the fuel level gauge is working). Not good, but I believe that you've got that a little backwards -- if the brown wire was shorted to ground = the gauge would wrongly read maximum all of the time (not be dead all of the time). Have you confirmed that the brown wire at connector C3 has a good connection to the terminal on the back of the oil temp gauge itself?
Yes that would be the case so I guess its not shorted to ground but the resistance is low (I guess thats normal). The brown wire is secure on the gauge. I decided to re-measure the grey wire at C11 with the engine running. Its not showing any voltage anymore whereas before it was ~+7V. This is for the water temp. I wonder what happened here? Its the weekend and I really would like to take the car out today but dont want to risk it.
I have a feeling the C11 connector is causing all this problem. It seems that the grey wire (water thermistor) is shorted with the yellow-green (alternator). C11 is in bad shape. It must have have been broken at some point both ends have been sealed with silicon. I will have to clean it up and separate it, (picture attached) but it will probably break. Any idea where I can find a new C11 and is it easy to put on? Image Unavailable, Please Login