My son has an 1986 bronco 302 efi and twice in the last 2 weeks overnight the seatbelt light comes on dimly and the eec relay starts engaging rapidly which in turn excites the fuel pump relay and runs the battery down
What I have done so far is change the eec relay and made sure the ignition switch is properly adjusted but it did it again last night?
Any ideas would be greatly appreciated
Thanks in advance!

 

Looking at the Haynes manual, the EEC relay contacts are fed thru a red fuse link. The ignition switch when switched on (electrically)(key on)- power the coil (EEC) closing these( EEC) contacts and power the fuel pump relay. If the ignition switch isn't causing the contacts to close- something is. As the print shows it can be pin 12 (ignition switch) pin 11(ignition switch).If you have changed the EEC relay ,my guess would be the ignition switch itself .The ignition coil is also powered by this switch -key on .TR