I have a Dick Smith Q-1419 multimeter and i just changed the battery for it. Now its measuring wrong. If i put it on a fully charged 9v battery is says 4.2v. I found a small knob that i can put a screw diver in to change it but is can only change it by about 2/3 of a volt.
Not a valuable multimeter - can usually get models with similar features for around 10-20 bucks.
When you've got it hooked up to your battery and it's reading 4.2V - I'd trying jiggling the range dial and see if it's position has an effect on the reading. If I was fixing it I'd check the wires from the battery, and clean all the contacts (especially behind the dial) - but if I wasn't having any luck within about 5-10 minutes - I'd just go buy a new one.
i did. i could only change it by about 2/3 of a volt
By the range dial, I mean the big one on the front of the case - where you select the measurement.
Underneath the front range switch will be a large circle of copper rings - I'm just wondering if there is a poor connection and it's causing it to do something weird. By 'jiggling' you might see the value change or read correctly.
