Ray -
I don't disagree with anything you have said. HOWEVER, I have been unable to find anyone that I consider reputable (including two Ford dealers and at least two transmission shops) that is willing to drill a hole in the transmission pan and install the fitting for the sensor. Some of them have simply declined without explanation, some have told me that they are afraid of the liability issue if there is a tranny failure in the future.
As I recall, you had to jump through some hoops to get yours installed.
By the way, some of these guys have also pointed out that a pan-mounted sensor measures the temp of the fluid in the pan (duh!), which is only loosely related to the temp of the fluid in the torque converter. And it is the temp in the torque converter that matters. I'm not sure what to make of that. I suppose any indication is better than none, which is what I have now. But let's agree that pan temp probably WON'T tell you if the fluid is getting so hot that it is starting to degrade - because the degradation is happening in the torque converter.
So that begs the next question. Where does the OBD-II system measure temperature? I believe that it is measured somewhere in the guts of the tranny, not in the pan. I say this based on the 600-page book of Explorer wiring diagrams that I bought from Ford. It shows the sensor as mounted inside the tranny, with the shift solenoids and the torque converter lock solenoid.
Finally, there is a subtle but interesting implication to the discussion of OBD temperature readouts. The fact that there is a temperature readout means that the vehicle already has a temperature sensor. You don't actually have to buy and install one! And in my Ford, anyway, it is analog to boot! I have been thinking about tapping into the wire that leads to the sensor - it is readily accessible in a connector on the firewall - and using it to drive an analog meter. I may not be able to screw up my courage, since the consequences of messing it up could be severe. But it is interesting to know that the sensor is already there.
Bill
|