1995 nissan pickup new alternator and battery

It is problem with main +ve supply for alternator from battery, fix new wire to alt to batt only for +ve supply and then try ,it will start charging,if it wont charge then problem with instrument cluster, only two could be cause.

Check the battery, make sure it's full,(if it's not sealed) then check the batt. for 1 or more dead cells.
The test is done with a hydrometer, to test specific gravity. If you don't have one they are fairly cheap at
any parts store, but if your going to the parts store
anyway, they will do this test and a load test for free.
If the battery checks out ok, check the connections
at the alternator if they look good, you may have a
defective alternator. I forgot to mention, that if you
have to add water to the battery for the specific gravity test, you will have to wait 24 hours for an
accurate result. Hope this helps. Good luck.