So, since I just had this problem with my rear window...and I happen to know electric motors pretty well.....check the contacts on the switches......I replaced the motor (as it was dead) but I still had intermittent issues with one switch or another....I am in process of removing, cleaning and snugging the wires/connectors and each time it gets a little better....the only other thing to really check is the wires, to make sure they have not been compromised....but switches are easier to start with and if it is old, mine is an 88 which was well loved by it previous owner, and even then man are those contact points dirty....
as for the window ECU, I defer to the vast knowledge of someone else, becuase I have not discovered anything like that...... as of yet...
good luck, and a boddington for good measure wont hurt...
