1995 ford ranger cluster problem?

Everything on my ford ranger cluster works but the rpms don't work except for sometimes it does but most the times it doesn't and i don't know what's wrong with it please help

Only guess is that it's a bad ground. Ford is notorious for it. What i did when my accessories and stereo display started doing funny things is I removed negative terminal, took a wire brush and cleaned all my ground wires. Everything worked perfectly afterwards