I swear I have read about this problem before, but can't find it in search. I was on my way home last night and it got cold enough my son wanted the heater on, so I kicked it on low. Instantly my overdrive kicked off! Shut the heater off overdrive kicked back on. What causes this? It's starting to hit that time of year when I need the heater again, and I don't want to fry my o/d.
Any help would be great thanks.

 

By looking at the wiring diagrams, they are on separate fusible links and separate parts of the ignition switch. Unless it has be rewired then it's anybodies guess.

 

Well in my search I have found 4 post referring to the same problem. Not one of them had a solution though.: Hopefully I can get it figured out.

 

Check the ground on the radiator support near the battery.