Add an outdoor thermometer to your car
I always wanted an external thermometer in my car. I find it useful for ice warning and general information.
Unfortunately, my 1999 Citroen Xsara mk1 doesn’t come with one. I had to hack it.
I bought the Auriol Internal – External Thermometer from lidl. It has Ice alarm, min/max settings, and long 3m cable. Everything you need from a car thermometer. It only costs 3.99€. Sweet.
The difficult part is finding a path for the external sensor cable. Of course you can leave it hanging by the door, but it’s not elegant, and eventually you will severe it.
Some choose to install it in the engine compartment but this way you get false readings from the engine heat.
After a lot of thinking, I ended-up mounting it inside the mirror. This way it’s very well protected, hidden, provides an accurate measurement, and it’s an easy path for the cable near the dash.
First step is to dismount the mirror. Check the forecast before you start. Rain is annoying.
Use a flat screwdriver to un-clip the internal bezel
Un-latch the controller knob to free the bezel. Take care not to break it.
Then un-screw the screws that hold the mirror in place. Make sure you hold it when you unscrew the last one, or it will fall-off.
So I removed the mirror and took it home. That left a gaping 5cm hole back at the car, but it shouldn’t be a problem unless you’ve got heavy rain. Fingers won’t fit through to disengage the lock.
The under-side. There’s a cap in there. Use any of these tabs to remove it with a flat screwdriver. This will give us a better view and access inside.
Carefully remove the blue cover to reveal the insides. Use a flat screwdriver, but make sure not to mark the plastic.
Inspect the lens-adjusting cables. The sensor cable will follow the same path into the car.
Thread it through the 2 entrances.
It will end-up on the rear side of the mirror, where the blue cover was.
Now test-fit where everything will be. Make sure there’s enough cable left outside of the mirror to mount the display anywhere you want it.
To permanently fix the sensor into place I used a two-part epoxy putty. It’s the same stuff I used for my gear-shift mod. When it dries it becomes hard as rock.
I also fixed a small crack I found that made the whole mirror to wobble when in motion.
Now re-fit the mirror on the car without putting the cover back on, to make sure that everything looks ok, the lens still pivots the way it’s supposed to pivot, and there’s enough slack cable for you to mount the display where you want it.
I super-glued the display on the door card. It should be easy to remove it in the future if needed.
To change the battery on the rear I need to roll-down the window. Easy enough.
Some final thoughts:
It’s more usable if you mount it somewhere on the dash in front of you. This way the information is there without having to take your eyes off the road. The problem with that is that because of the movement of the door, the cable will show, which makes the setup a bit uglier, and more importantly, it will wear fast.
Also, note that my car is a left-hand drive. The way the thermometer is mounted, the display is under an angle and makes it a bit hard to see depending on the lighting. In hindsight I should have installed it on the other mirror on the right side, so that I can look at it across the car as it would face the driver.