I recently purchased a used 1999 model 453 with 1250 hours on the clock. I serviced it, and cleaned it up as it was used in the Pentagon after 9/11 cleaning up the inside of the damaged building. I noticed after about 12 hours of use, that the light on the control panel that has to do with the hydraulics flashes, more so at idle but also a little at full throttle. I have changed the hydraulic oil and filter to no avail. What is going on and what are the consequences if I continue to operate the machine, as it runs OK and is not losing power or capability?