airtronics rd8000 problems

[1985 kenworth]

hello i need some help here ,i am stumped .i have a tractor that has the rd 8000 radio on it .everything was working fine 2 weeks ago .i turned the radio on a few days ago to run the truck and i got nothing.the mfu unit is centered for the function to operate as this was never touched.i turn the truck on and at first the steering would go to the left and thats all that would happen.no functions at all.so i tried plugging another mfu unit in ,just thinking the mfu was the problem but i still get nothing ,no lights no mfu unit starting up .can anyone shed some light on this.obviously it is not the mfu unit but could it be that the radio is unbinded itself from the receiver possibly.not sure how to bind this radio ,any and all help or suggestions taken..thanks...at my wits end with this