With the recent cold weather, furnaces and water heaters often will not start. In cold weather, the quality of the electrical connections can determine whether you will have heat or hot water. The first step is to carefully clean the copper circuit board terminals using an ink eraser to gently clean them. Then lightly "scratch" the metal tabs within the white push-on connectors using a fine screwdriver tip or awl. The "solution" is to then apply just a drop of Corrosion Block® on each terminal connection and reinstall the connector. That should keep the corrosion at bay for 18 months or so.
On all push together connectors simply pump a drop or two of Corrosion Block® at the junction of the two halves of these connectors and watch it wick up to protect each one. If you have them apart for other reasons then apply Corrosion Block® before reconnecting them. I do not recommend taking them apart unless there is a specific need to do so.
Check out each of these Tech Tips for further information: #8(furnaces), #32 (both water heaters and furnaces), #35 (water heaters) and #41(Info on Corrosion Block®). Keep warm and have a hot shower!