I had to boost my 96 Diesel Dodge yesterday. It does get run alot but that is beside the problem. The batteries are only a few months old, so that is not the problem. This has happened before but only in the colder weather.

I am assuming that the problem lies in the heater. I am assuming that it is getting the signal to run when the truck is not on, hence running the batteries low in the truck.

So my question, after a long winded explination, is which relay under the hood can I unplug so that the heater shouldn't run. AND after it is unplugged, is it imperative that it gets plugged back in prior to the next time I run the truck?