The sensor is as old as the truck Darrel. Also surprised that there was only one other owner who said they had the same problem considering the age of our trucks. I'll get a price for a new sensor beffore I try to check out the wiring. May be a while but I'll report back on progress. Thanks again for all the help.

 

Darrell-
Would you think that a display that shows only -40*F is also an open circuit?

Thanks,
Drake

 

If the readout on the console never changes, there is something wrong. I cannot say whether it is an open or short in the circuit. That is why we test, although some just swap parts. Throwing parts at the problem is the expensive way.
I don't know which way the circuit board is set up on each model. The interpretation of the resistance from the sensor is determined by the way the circuit board is built. The same resistance could be shown as either 140 or -40, depending on how the electronics on the circuit board are put together.

 

Throughout this thread, I have ignored the possibility of the electronic circuit board having issues. I KNOW that some console circuit boards DO have problems, since there are plenty of posts on FTE about it. There are posts on how to fix those boards as well.
I also have seen a few sellers on ebay that have refurb boards for the consoles in the Ford SD trucks.

 

I do know for a fact that my board is good since I just got it back from a popular ebayer who refurbs. them. His ebay name is Warhl.

When I sent mine to him it was blank. The only issue I'm having now is the constant -40*F outside temp. reading. I will do the resistance tests you suggested earlier Darrell and see what I find.

It could be that others may be having issues with their boards though.

Thanks,
Drake

 

Darrell-

I took a continuity reading from the ground wire plugging into the overhead console and the two ends that the sensor plugs into. Neither gave the beep on my meter indicating continuity. However, when I went to read the ohms, one wire read 7.49 kohms. What does that tell me? I happened to be using a 10 - 15 ft jumper wire to reach to the front of the truck. I don't know if that makes any difference when I am doing this or not.

Thanks,
Drake

 

Not sure I understand.
You ohm out the wires that are attached to the sensor from the overhead, correct? You should get an ohm reading. If no ohms, jumper the wires at the sensor end (without sensor) and re-ohm the loop from the overhead. If you get no ohms at that point, bad wiring. If you get ohms with the jumper wiring, wire loop is good.

If you get ohms in the jumper wire step, unplug the sensor and ohm ONLY the sensor. Sensor range should be 100 to 150 ohms, depending on ambient temps. Above or below that, the sensor is bad. Ohms through the sensor only should be close to ohms through the sensor loop (with sensor) if the sensor is good.

7,490 ohms (7.49kohms) means you have high resistance somewhere. Much more than you should. That is a bad connection if it is just wires. If it is only through the sensor, the sensor is likely bad. Which wire pair did you get that reading from? If that reading includes the jumper wire, you may not have had a good connection.

The ground wire should be low resistance to ground. The sensor wire loop without the sensor, and jumpered at the sensor end, should be low resistance with NO continuity to ground.

 

The wire that I got the 7490 ohms was the ground beginning at the overhead console plug to the other end where the outside temp sensor plugs in. Obviously taken with sensor removed. Was I following a path that should have shown continuity or only an ohm reading? I will have to ohm out the sensor by itself later tonight or tomorrow morning and ill let you know what I find.

Thanks,
Drake

 

If that was a single wire as stated, you have problems in the wire. That wire should have continuity, with very low resistance. I'm guessing around .203 ohms total (or less) would be about correct. If that wire was 20ft long, it would mean 374.5 ohms/ft. 18 gauge annealed copper wire is .006 ohms/ft. That section of wire is possibly frayed, pinched or you didn't have a good return loop.

The wire specs are from Uglys' Electrical Reference Book.

 

Better weather has permitted replacing the ambient air temp sensor which appears to have soved the problem of 140deg temperature shown on the OH consol. Ford part # F87Z12A647AA $44 plus tax at dealer and Oreillys #WT3098 for $22 plus tax which I used. They had to order it in as didn't carry in stoe. Hopefully will continue to work. THanks for help with location pic. Just needed to remove grill to replace. Some screwws on top and two clips to pry up with big screw driver on bottom.

 

I wanted to update everyone on my overhead console outside temp. sensor reading -40* all of the time. I already figured out it was a ground, but I discovered exactly where the open ground was at the same time I was trying to resolve a problem with my fuel gauge stuck on full and my coolant gauge not working.

Turns out it was in a connector just under the dash on the driver's side towards my right knee when sitting in the driver's seat and just behind the fuse panel.

It all works now. I'm very happy that I was able to figure this out.

Drake

 

I . ?

 

This is for the Intake Air Temperature (IAT).

This one is for the ambient temperature for the overhead display.

 

My overhead display is accurate once in a while. When it hits -40F, it is RIGHT ON! LOL