CTEK makes nice chargers, but the "Mode" button can stop working properly, rendering a fairly expensive charger useless or just plain difficult to select the mode. The family and I have lots of these chargers that are many years old, some are in open sheds/carports year round. Two have eventually needed this fix. Buttons are common problems that can often be relatively easy to repair with some practice, and with this step-by-step write-up it will be really easy!

1. Usual safety warnings, blah, blah.

2. Remove the screws that hold the case together. Pull both the cord strain reliefs outward, just enough to allow the circuit board to rotate. The button switch, which is activated through a membrane in the top, will become visible. The toothpick is pointing to it below.

3. One can try cleaning by spraying some plastic safe cleaner or alcohol into the switch, turning the button, and drying with a hair dryer -- Then test, and put it back together if that works.

4. If that doesn't work, no problem. Pull the button apart from the housing which is soldered onto the circuit board. If the large diameter button part comes off the stem, put a drop of super glue on it, push it back on, then pull the guts of the switch out. There are four tiny plastic tits that hold a metal retainer that must break off, which will be super glued back later. Below is the switch housing with the guts removed.

And below are the guts removed from the switch. The small brass disc bridges the contacts in the switch housing, and also functions as the spring for a tactile feel.

5. Clean the switch parts, and sparingly apply Vaseline PJ (Petroleum Jelly) to the disc and contacts with a toothpick. PJ obviously isn't required, but it's an old trick to make this switch last a long time. Use it for potentiometers and switches that have low voltage -- inhibits corrosion but still allows good conduction. Put some PJ on the stem of the button as well so any excess super glue used later won't stick. Don't get any PJ on the metal retainer, or where it will be super glued on the switch housing.

6. Assemble the switch. The convex side of the disc goes away from the bottom of the switch so it acts as a spring and bridges the contacts when pressed. Press the button while getting the metal retainer aligned on the plastic tits, and then sparingly apply super glue at the four corners. Test the switch, and admire your work. Below is a side view of the assembled button switch.

7. All that's left is rotating the circuit board back in position, pushing in the strain reliefs, fastening the screws, further admiring your work, and reminding all household members of the vast amount of money saved.