Golds gym cross trainer g451 no tension?

I have a Golds gym cross trainer model no: g451, which seems to have no tension. The computer unit switches on, but the machine is very 'easy' to use with no tension, no matter which level you select. All of the counters show 0, instead of showing your calories and distance etc. The motor appears to be making a noise likes its changing settings, when you change the level of the tension. But there is actually no change in the tension. I have opened up the main section of the unit where the motor and belt is, and the belt is very loose on the wheels. I am not sure if its simply a case that the belt has 'fallen' off somehow? or that the belt needs replacing, or if its nothing to do with the belt. I have tried hooking the belt around the large wheel and 2 small wheels but its still seems loose. The motor seems to be working ok, but again, I can't be sure. If any one could help at all I would really appreciate it.