Coleman watch Model No. 40-328 How To change from 24 to 12 hour

Look at the manual for this.

Click on your watch model number to open the instruction sheet below.

Your model number is located on the caseback of your watch

go here> http://www.gsi-usa.com/instructions/

See this Coleman website for the full instructions:
http://www.gsi-usa.com/instructions/SB-429A-EN.pdf

I don't know the detail of your watch operation but this may help:-

The "mode" button steps the watch through a series of settings which can be adjusted by pressing one of the other buttons.

Keep pressing the mode button until you reach "24" or something similar and then experiment with the other buttons until it changes to "12".

It may require a little patience but in the absence of any instructions you should be able to work out the correct sequence.

Good luck and don't give up!

The watch has four buttons. The lower left button is labeled MODE on the face of the watch. There are four modes and pressing the MODE button will step through each mode until you return to the mode at the start of the process. Start at the "Normal" timekeeping mode and press the "MODE" button three times until the digital display rightmost two figures for seconds flash.
Press the lower right button labeled RESET until the item you want to change is flashing. Pressing RESET cycles through seconds, minutes, hours, day, month, day of the week in the top sub-dial and then back to seconds again.
When the item you want to change is flashing press the top right button labeled START to step the displayed item to the value you want. When you are satisfied all the settings are correct, press the lower left button marked MODE to return to normal operation.
Coleman 40-408 User's Guide

think of the top buttons from left to right as A & B and the bottom buttons from left to right as C & D. The way to turn the chime off and on is by holding the C & D Buttons simatainiously and the pressing the B button. This will allow you to turn the Hourly Chime Off and On. When you see the digital chime pattern in the display the chime is on. When no pattern is shown the chime is off. Hope this helps the ton of people who have purchased these watches & either did not have instructions with or lost them. This perticular watch has been annoying the whole household for quite sometime and has now been put to rest..lol

The manuals for Coleman watches are at this website. . .

http://www.gsi-usa.com/instructions/

You need to look at the back of your watch to get the model number.

If it is the same as mine just hit mode once to go to the date screen then hit start

From the instructions that came with the watch:

Press the button at the top left to get into time change mode, press on the bottom left button to move between seconds, hours, minutes, etc.

Press the top right button to change numbers; hold to move quickly.

Go up a level, then select your model.

http://www.gsi-usa.com/instructions/

I found my Coleman 40-842 there.