Chances are good that the meter movement has suffered physical damage,
or has had a mechanical part failure.

Damage can be related to harsh handling or misuse. Checking a battery
voltage that exceeds the selected range/type can cause irrepairable
damage. In many cases, this will open the moving coil windings (fuse
action).

I suspect that since the meter will deflect down-scale (as well as up),
that the problem is a damaged hairspring. There are almost always 2
hairsprings, which are wound in different directions, at each end of
the armature.
As each hairspring tension opposes the other, if one were removed or
weakened, the other would be stronger, moving the pointer "harder" in
that direction.

If the meter movement isn't the moving coil type, then a hairspring or
the band has possibly been damaged (weakened or distorted) by
overvoltage or misuse.

If the meter wouldn't deflect down-scale, I'd suggest that the problem
might be a small bit of debris inside the meter movement that was
stopping the coil from returning to it's zero position. Sometimes a
small magnet flake or other material will cause this.

Resetting hairsprings is (not can be) a very delicate procedure. Meter
manufacturers used to actually list hairsprings as replacment parts.
The tension needs to be precisely balanced for a precision meter
application. Many armatures also utilize counterweights fitted on pins
that extend outward radially.

If it's a separate panel meter (not built into the tester's case), and
you can see some numbers on the meter, you may be able to find a
suitable replacement meter assembly. Many meter movements have a full
scale current value printed on the meter faceplate/scale plate,
something similar to 100uA DC F.S. (full scale deflection at 100
microamps).
For using meters of different ratings as substitute replacements, refer
to books covering meter shunt resistors and similar topics.

Cheers
WB
.................

Mike Muderick wrote:
I have a battery tester meter (Mallory) that came from a retail store. The
meter is magnetized and now sits center scale, instead of over to the left.
Any solutions to return it to it's normal state. I tried reverse polarity-
it goes to the left, but then returns to center.

thanks