I just fixed mine yesterday. I was doing the EXACT thing on my 54 ton truck, with the foot under the brake pedal.
On my truck there are two springs attached to a bracket mounted to the side of the frame. One is for the clutch and the other one is for the brake return. Now, what I did was take the brake spring off and cut off about 3/4 of an inch off of the long end and bent another hook on it and this added more tension on the spring and worked like a charm. I even tried bending the switch arm some so the brake arm would make contact sooner and would start breakig the contact, didn't work. The cutting off the sping trick did the trick. I suppose after years of use the spring gets weak and doesn't have the tension it had at one time.
Good luck,
John Niekamp
