Do you remember the song “Take it on a 10 day trial”? We’ll go for 30 days… We do not guarantee that this device will fix your problem, or that you cannot have problems in using it. The device operates from a 9 volt battery. It should NOT be used if you are pregnant, or using a heart pacemaker, due to insufficient testing for people with those conditions. We have not done clinical testing, or double blind studies. We are not treating disease, or prescribing treatment. We provide a device that allows you to do your own testing. However, if you are not happy with the device, we offer a 30 day money back guarantee. If you happen to live in our city, and you return it to our premises within 30 days of your purchase, we will refund the amount of your purchase. If you live elsewhere, we can ship it to you, and you can ship it back, but any refund will exclude third party shipping cost. For the warranty to be valid, you must have filed with us at the time of purchase, a signed copy of the invoice for the product. We ask that you state the reason for your return, so that we can correct any issues possible. The red light will flash if the battery is low when the zapper is turned on, and if you touch the two probes to the contacts on the side of the zapper at the same time, the green test light should come on. If the green test light does not work, your zapper needs repair.