I have a hobbico digital voltmeter and it is about 8 yrs old never dropped or mishandled. When I go to check out my rx batteries the volt readings go up and down as in malfunctioning . I changed the 9 volt battery and still has the same thing . if I switch it on and off and get it to read steady 0 v then I get a solid reading . Do they wear out over time there's very little that can wear out . could my switch be bad ???? Please advise and thank you in advance for all your help ...
Ken

Use a new set of wires/leads. You could have a probem in one of the bananna plugs. Very common problem.

I think I would be very glad if I could say if mine lasts a full 8 years.  Mine is around 2-3 yeqars old and works just fine.  Its just that I worked avionics for 31 years and I am used to a much higher quality voltmeter.  A fluke or a simpson are built to last.  Maybe I am wrong but my Hobbico looks and feels like it was made to be replaced fairly soon.  All that being said K-Bob is right.  Often times its just a lead problem.  Can you take your banana leads apart and check the connections?  They may have worn thin and need re-soldering. 

my banna plugs worked perfect on my radio shack exp scale meter but no load that's why I don't use that good meter . thanks for the heads up on the plugs guys I appreciate your help this is such a great site.

Ken

I use the Heathkit expanded scale voltmeter I built in about 1972 when I built an 8 channel Heathkit R/C transmitter. The meter has no battery, as far as I remember. It works perfectly. Every time. That is 39 years!