Fluke8840A stuck at value DC

[gossamer]

I got a Fluke as used/working item. Self test is passing without any errors. Measuring voltage seems fine, it gives what looks like a reasonable value (can compare it only to handheld MM which shows approximately same value).
The problem is when I set meter to Digit6(Auto), Digit2, Digit1 mode on DC voltage measurement, it is showing OK value from the power supply. Changing the value up/down on PSU settles fast on the fluke. Seems to be operational. But, when I unplug the lead it get stuck to that value and it starts to drift toward +Inf. Interestingly enough, Digit3, Digit4 and Digit5 mode get reset to 0 after unplugging the leads.

Didnt have a chance to crack it open. Any suggestions how to troubleshoot this issue ?

Thanks

[Kean]

That sounds completely normal.  Selecting those different modes is changing between the various fixed (or auto) voltage ranges.
Per the manual, in 200mV, 2V, and 20V ranges, the input impedance is very high - 20Gohm,  vs the 10Mohm in 200V & 1kV ranges.
With such high impedance, it isn't at all unusual to see this drift.

[Specmaster]

I agree, its perfectly normal because of its exceptionally high input impedance, I have 2 of these lovely meters. If your in any doubt about it, after disconnecting from voltage source, touch the probe tips together and the display will zero and as soon as you seperate the tips, the display will slowly increase again due to EMF field in the air being picked up by the leads.

[gossamer]

Spot on. As said, touching the probes together zeros the input. It starts drifting again after.
Makes sense 

Thanks for pointing that. I suppose I should download the manual