Polar mohr 92 EMC error 87

Hi,

We are getting an error 87 intermittently on our Polar Mohr 92 EMC, to reset we will shutdown the unit and power it up again. At one time we got and error 90 too.

where can we find or buy a service manual for this unit that would have the error code detailed and explained.

I was told that it indicate that the knife in not in the fully up position. As we can reset it by shutting it down, I'm suspecting that the problem is electrical and not mechanical. I'm suspecting that the problem is on the feedback circuit, either a relay or switch. If so can anyone tell me where it is located?

Thanks,

vaughan