Changing a watch battery in a Gruen Precision watch is a straightforward task that requires few tools and little skill, but caution should be exercised. Quartz Gruen Precision watches are low to moderately priced timepieces powered by a battery. Contemporary Gruens are produced by M.Z. Berger and Company, which had purchased the Gruen name to market its products. These Gruens are not related to the original Gruen watch company that ceased operations in 1957 and never manufactured battery-powered watches.
Use the case blade to pop open the snap-back Gruen Precision watch. Use a jar grip opener if the case back is a screwdown model. Secured by a side-mounted spring or a topside flat strap is the battery, which is a small silver disc. Insert the screwdriver between the battery disc and spring and loosen the battery. The battery will easily come out. Use a screwdriver to loosen the screw that fastens the strap over the battery if the watch is the strap version. Do not remove the screw, but simply loosen it. Remove the battery using the tweezers.
Use the jeweler’s loupe to read the voltage size on the battery. It is likely a 1.5-volt alkaline or silver oxide battery. Both are efficient batteries and it makes little difference which is chosen as a replacement.
Use the battery as a guide for the replacement at any watch repair shop. Cost is usually under $5. Remove the battery from its packaging with the tweezers. Try not to touch it with your fingers, which contain oils and contaminants.
Hold the new battery with the tweezers in one hand and use the screwdriver in the other to push back the retaining spring. Insert the battery in the holder. If the battery is held by the strap, move the strap over the battery and tighten the screw with the screwdriver.
Snap the case back into place and ensure that it’s flush. Use the rubberized jar grip opener to tighten a screwdown case. Ensure it’s tight. A case press can be used to install the case back, but the device can be expensive and is only recommended for watch enthusiasts who routinely service their watches.
It’s possible to replace the battery without tools by using your fingernail instead of a screwdriver or case blade and your fingers instead of tweezers, but only if your hands are clean. It's not recommended.
Do not force open a case back or a battery from its holder under any circumstances. You will damage the watch. Take stubborn watches to a watchmaker for a battery replacement.