External Air Temperature Troubleshooting

[mockfish]

I've got a 97 Limited with the 4.0 SOHC.

My overhead computer display has started reading the outside air tempature incorrectl, including saying the old -40 degree reading from time to time. I did a litle research and here and everyone seemed to think it's the ambient air temperature sensor. So after calling three dealers and getting a large spread in price for one (from $21 to $101!), I bough a new motorcraft one and put it in. It did not change the problem.
Does anyone have any other ideas? I did notice there was another "plug" looking thing on the same wiring line as the Ambient air temperature sensor that snapped on to the frame somewhat close. I also notice a picture of what appears to be the same "plug" in the photo gallery titled "temp sensor 1", "temp sensor 2", and "temp sensor 3". (Sorry I don't know how to paste it in) I pulled it out and it had a old part number on it that said "D9AB-14489-CB"

Anybody know what that "plug" thing is and what it does? I can't find it in my Haynes book, and Ford dind't seem interested in trying to figure it out at the parts counter. Do you think that's it?
Any suggestions? Thanks!

 

[Stic-o]

The Sensor should look like this. It should be right above the Driverside airbag sensor above the frame rail, behind the grill. Napa has them for $21.49 Part # ECHTS5047

The other part you stated above with the pictue "temp sensor 1-3" is actually just the plug in for the sensor. As for why it's not working? Not sure. It could be the overhead itself. I just installed the overhead in my truck, and it seem to work ok. but not as acurate as the one in my wife's volvo.

 

[mockfish]

Correct "Stick-o", that's the sensor I replaced.

The new sensor worked just like the old one. All over the board and not reading correctly (e.g., 10-20 degrees under the real temp to minus 40 degrees). It seems like it would have to be a signal sent to the display, right???

What do you mean the other plug is "the plug in for the sensor". What does the other plug do then?

This is really bugging me. Thanks!

 

[Stic-o]

I ment this piece. I think this is just the plug in for the sensor. My truck does not have one because I kinda just wired in the sensor. My truck did not come with the overhead originaly

 

[mockfish]

We're talking apples and oranges then. I'm not talking about the plug the ambient air temperture sensor goes in, I'm talking a different plug/relay thing that is connected to the same wiring, and attaches a little below the temperature sensor (Which is up by the left headlight), and still snaps into the frame. I unplug it, and the overhead reads -40 degrees. I plug it back in, and it reads all over the board including -40.

 

[Stic-o]

Now that is interesting. I'm not sure what that is. I wired mine straight into the overhead. Brown and green wire. Nothing in between. It's not for wind speed, because that is a seperate wire from the overhead. I wish I could help more. It sounds like a wire is lose some where. Before I hooked mine up, it did the same thing yours does.

 

[mockfish]

I'm still open for suggestions. Anyone? I'm stumped.
Thanks.

 

[Homerexplorer]

A reading of -40 indicates that the circuit is broken (I know, duh)- or at list broken intermittently - either a bad sensor or a bad connection. A bad connection would explain why it fluctuates, sometimes working, sometimes not, sometimes in between. It's like a bad ground on a tail light - it can cause the tail light not to work at all, work sometimes, or in some cases work but be very dim. It sounds like you have the same thing going on with your temp sensor. A thermocouple (temp sensor) works by sending a millitvolt signal and a bad connection will cause an erratic or erroneous reading.

I would disconnect the sensor and put some dielectric grease in the connection, then plug and unplug it several times to remove any oxidation. If this doesn't help, get a helper to watch the readout (system on) while you carefully wiggle the wires (be gentle) where they meet the connections. You're trying to find the bad connection and you'll know it when the temperature jumps. You'll want to do this for each connection in the circuit. It's frustrating like a bad ground. Good luck

 

[mockfish]

Nice suggestion Homerexplorer. I'll try it.

Anyone else?

 

[mockfish]

A quick update. I tried calibrating it (which I didn't know about before) and it seems to be working for a while (couple of days), Every now and then it puts up a wild temperature but seems to go back to normal. If it gets stuck reading bad temeratures, I calibrate it again, and after a day it's back to normal.

I actually put the old sensor back in originally because they both seemed to do the same thing (Pre calibrated). Should I have originally immediately calibrated the new sensor when I put it in, or should it in theory have worked right from plug in and driving for a bit? I'm considering going back , buying a new one, calibrating it immediately, and seeing if it ever gives me bad readings again.
What do you think?

 

[df_EB2000]

I have been having a similar problem since I got my Ex used last year. Except mine seems to consistently read 6-10 degrees high. I too replaced the sensor to no avail so put the old one back in.

How did you calibrate the temperature?

I have been frustrated with this problem as well. When I had it in for a check, ford says the overhead unit must be faulty? No explanation, just that.

 

[mockfish]

Just hold down the middle mode button until it says VAR. From there i kind of guess a bit you can finally get it to say CAL. You push it a couple of times to get a random number. Then after about a day it goes away and reads ok. I'm sure someone can clarify the process better then that. Sorry!

Hope it helps

 

[pj8847]

Actually the "CAL" setting on the overhead console is for the compass. Each number represents a certain magnetic geographical location. It uses this information to calibrate the compass to display direction correctly.

the only thing you can change as far as temp. is the display of either Celsius or Fahrenheit.

As far as your problem with intermittent temp. fluctuations and erroneous readings, it is definitely either a wiring problem, or the overhead itself is malfunctioning.

 

[budwich]

the temperature sensor is just a simple thermistor that varies its resistance with temperature. With the sensor plugged in, unplug the connector at your overhead console that is going to the sensor. Take a meter and measure the resistance. It should be stable and either high or low... can't remember which... I think high for cold and low for hot. Anyways, in 96 (my drawings), there are three connectors in the circuit so you could have problems along the circuit route. Next, get a helper to hold the sensor in their hands while you measure the resistance, the resistance should move and go in the direction indicate (low???).

 

[mockfish]

Thanks for clarifying the "CAL" reading. I guess I'm back to jiggling wires and trying what Budwich suggested. Thanks again.

 

[rweyant]

I am having the same prob, in for the results..

 

[TongueTied]

Overhead readout ...

"I am having the same prob, in for the results.." - me too - my 97 Eddie Bauer - the compass works fine - but the ole -40 degree thing - do we have a definitive answer?

Thanks

 

[orangeX]

Hi guys. I have the ford #DY841 or NAPA ECHTS5047 outdoor console sensor. I have had the console temperature reading correctly or as high as 60 c or 140 f. I understand when it reads 60 C or 140 F that the temperature sensor wires are shorted. I have checked the sensor's resistance and it was OK. I put my other explorer sensor in its place and it works. I think it is the plug or wiring harness. Can you guys have me the correct test precedure to find my problem or short. Is the vehilce ground used in the circuit or are the wires separate. Tks.

 

[budwich]

Not sure that I quite understand but I assume that you unplugged the external sensor (near the bumper area)... right? Then plugged in another sensor, and the reading was fine. Hence, it would "appear" that it is testing out the wiring all the way back to the console. Probably true. The sensor has two wires (at least in 96 drawings). I would suspect a bad /marginal wire near / around the plug area which you might have disturbed when you did your swap / check OR a bad / marginal sensor that works some time and not others. Try a hair dryer on it and check if it goes "short" when it warms up... measuring right at the sensor.

 

[TongueTied]

Ok ..been a Long time ...

and still have the same problem; Overhead console reads -40 degrees all the time ...not sure how we said to fix this ..but ...help? someone have a definitive answer for this? If so ...educate me??

Thanks to all

TongueTied :exp: