Home Thermometer Modification for Air Conditioning Inspection - Temperature Split.

A very simple modification to a dual-scale (indoor/outdoor) household thermometer, which I have used for many years when annually checking the air conditioners at home. Of course, there are specific thermometers on the market for air conditioner use, but why not do it with something simpler?

If you have an old thermometer at home, you can always use it. I used to leave mine on the air conditioner or hanging from the cable, but it would always end up falling to the floor.

I thought of an improvement to be able to comfortably use the household thermometer I already had, instead of buying another one. This improvement consisted of adding “a hook”—a moderately thick wire shaped to fit the side of the air conditioner unit—which allows for easily checking the temperature differential of the air conditioner.

And checking if it is working correctly with at least a 15° difference between the air intake and output.

The thermometer used is an inexpensive, dual-scale household model with a wired probe. The important part of this tutorial is the idea; then, each person can adapt it to their particular thermometer.

I use a 2 to 3 mm thick wire, a piece of black heat-shrink tubing on the end of the hook so it doesn't scratch the device's housing when hooked into the top grille, and a screw with washers and a nut on the thermometer's housing.

In my case, since I have 3 identical units, I made a specific hook with the most suitable shapes for the side of my home AC units. (Right angles don't work well, in case you were already thinking about it).

Photo 1: Detail of the back of the thermometer, I have reused the screw hole where the device would be hung.

Photo 2: Detail of the wire, as you can see it is bent to match the center axis of the box so that when hung, the thermometer box does not tend to rotate, you cannot know or take this into account until you perform tests, (As you can see, even the simplest thing has its little secret or detail).

I attached an unused alligator clip to the temperature probe at the end of the cable and secured it with heat shrink tubing. If you don't have an alligator clip used in electronics and electrical work, you can use a clothespin or make another type of hook; it's all about seeing what you have and using a little imagination.

What do we check with the thermometer in the air conditioner? THE THERMAL DIFFERENTIAL, it is a basic check of its operation, we measure the ambient temperature and the supply temperature of the cold air stream.

Guidance video I made 12 years ago On the thermal differential as you will see, without the modification made, the thermometer was much more complicated to handle.

This other video is more current:

Other complementary checks performed on an air conditioning unit, but not included in this tutorial, are measuring compressor power consumption with a clamp meter and measuring gas pressure with pressure gauges; however, these measurements require specific tools and knowledge.

The focus of this tutorial is the thermometer; thank you very much for your interest in reading it.

END of the Guide.