I never did any of this on my 9860 and now my 9870.I just went through the header calibration and it works great, everything.Not completely true. First you will have to find the right address to turn off the accumulator system. Next you have to change the height range from reading 100 inches to 50 inches....this is another address. Next you will have to dial in the header height sensitivity....yet another address. This all sounds like a lot but if you find the right Macdon dealer they have all this info in manual. I changed all this in our 9860 the other day in a few minutes. Once getting all this set and calibrating the head the header height system works great. It stays pretty much locked on whatever height you choose.
Well then you lucked out. Mine always seemed slow to react so I went through the set up sheet that Mac don has for JD 60 and 70 series combines. I found out that my sensitivity was set as slow as possible, around 150. Mac don book said the normal range for their head was 60-80. I set the sensitivity to 60 and now it works like it should.I never did any of this on my 9860 and now my 9870.I just went through the header calibration and it works great, everything.