[mycbarnes]

Lots of discussion on merging of the house and engine batteries on other threads. I just changed my merge relay for a couple of reasons, it was old, hot and it had some internal resistance across the contacts producing a voltage drop. I think Newell recommends changing this relay every year. So I cut mine open to show why. It is a simple coil magnet plunger with contacts. The contacts were pitted and burned a little, the contact disc was the same.You never know when the next closing will either weld together the contacts, or the coil fail to pull down the plunger from heat damage. The part for mine was a Cole Hersee 24106 found easily on Amazon. It is very easy to change. But I recommend disconnecting shore power and batteries isolated first. A short to ground while energized will be same as a welder.