Mirror temp readout inaccurate.

[JimInRadfordVA]

Every time my wife gets in my '05 Trailblazer, she laments the fact that the rear view mirror does not have a temperature display.

Finally got around to installing everything now that the rain has stopped!

Everything went in fine. Compass is calibrated and the temperature works, BUT it reads ridiculously high. Actual temperature was around 58F this morning. Mirror read 101F.

What is the best way to troubleshoot this? Does anyone know what the electrical output of the sensor should be? Can I toss a resistor in there somewhere to check the mirror itself?

 

[Mooseman]

So was all the wiring there or did you have to put in your own, like @$ Khalid ! 9130 ? My guess would be a wiring issue. I know us guys with the digital HVAC and the reading is whacked, we pull the HVAC B fuse for a bit to reset the system.

 

[$ Khalid ! 9130]

Hi

Good to hear that the sensor reading is working. If you look at my build thread u can see that I put it in the wrong place as the sensors clips were all broken. And since when I start my car I get the normal reading of the temperature outside. However after the engine starts running for a while the reading shoots up. I plan on buying a new sensor and placing it in its right position by the radiator shroud. Am not sure if this is the same problem you're having, but I just I'dlet you know

 

[therealsethallen]

I've found that the outside temp sensor can (over time) become a little flaky and fail. It sits somewhere underneath the front radiator crossmember. ACDelco 25775833, it's $5.69 on Amazon. I'd spray the piss out of the connections with dielectric grease and install a new one to start.

 

[JimInRadfordVA]

I had to add everything: mirror, pigtail connector, sensor and wiring.

I know the sensor is in the right place. $ Khalid ! 9130, the display starts out high, say around 51c and moves up and down a degree or two. It does not heat-soak and increase as the underhood temperature increases.

I'm going to re-crimp and solder all the connections again and see if that helps. If not, I'm going to throw another sensor at it.

More as it develops.

 

[Mooseman]

Try unplugging the sensor. You should get an error or something other than a reading. If not, then there's possibly something with the wiring.

 

[JimInRadfordVA]

Tried that. Got the "OC" readout. Wiring seems OK. Still, I'm going to re-work it just to be sure, then try another sensor. They are cheap enough. If I had someone local who had the same mirror, I'd plug it into their vehicle just to make sure it isn't the mirror.

 

[JimInRadfordVA]

Went through the wiring today. Cut out all the crimps. Soldered the connections, shrink-wrapped them individually and bundled in shrink-wrap as well. Checked routing and added zip ties as necessary. Nice and neat.

Digital readout still shows about 35F too high. Next step: new sensor.

 

[AtlWrk]

Sorry I'm a bit late to this. Did you get a new sensor installed?

In case other come to this thread looking for help I checked my sensor last night and it read about 5.3-5.6kOhm at about 77-80F. Usually these are negative temperature coefficient (NTC) sensors so any additional resistance caused by wiring problems, corrosion, bad connections, etc. should show up as an abnormally low temperature (NTC=temp goes down-->resistance goes up), not high. So I doubt wiring was your problem.

 

[JimInRadfordVA]

A few days ago, I installed a new temperature sensor. Success! Mirror was reading in a reasonably accurate fashion. Yesterday, however, the display went wacky and now all the LCD segments are lit.

I'll post a picture shortly.

 

[JimInRadfordVA]

A few days ago, I installed a new temperature sensor. Success! Mirror was reading in a reasonably accurate fashion. Yesterday, however, the display went wacky and now all the LCD segments are lit.

I'll post a picture shortly.

 

[$ Khalid ! 9130]

Oh no. I would be like the guy in your profile picture right now . Is it like that always or only when you start the car ?

 

[Mooseman]

Have you tried unplugging the new sensor as this seems to be the only variable. It looks like the mirror display is in perpetual test mode or has failed.

You have chosen the perfect avatar. Seems to fit well.

 

[JimInRadfordVA]

I tried unplugging it at both the sensor and the mirror. No joy at all.

A few days later, I started it up after having the battery disconnected for an unrelated matter and all was well again!

Except, the compass has the CAL light on next to the readout all the time. I've driven in circles for quite a while and the CAL light is still on.

 

[coolasice]

I tried unplugging it at both the sensor and the mirror. No joy at all.

A few days later, I started it up after having the battery disconnected for an unrelated matter and all was well again!

Except, the compass has the CAL light on next to the readout all the time. I've driven in circles for quite a while and the CAL light is still on.

your mirror might have some cracked solder inside it, mine did a similar thing and still does randomly.. opened it up and looked at the larger surface mount resistors and low an behold almost all of them had cracked solder on one side. resoldered them down and it works fine, still occasionally resets itself when cold. I'll crack it open again at some point and resolder some more.

see here: http://www.the12volt.com/installbay/forum_posts.asp?tid=133501