How do i fix the tachometer?

It's possible that the 2004 Ford Ranger's engine or the tachometer itself is to blame for the difficulty you're describing with the tachometer reading. A crankshaft position sensor issue is one typical reason for a tachometer to read high. To determine the engine's RPM, this sensor transmits signals to the engine control module (ECM). The tachometer may show a reading higher than the real RPM if the sensor is broken.
There are several possible causes for this issue, including a problem with the tachometer itself, a problem with the sensor that sends information to the tachometer, or a problem with the vehicle's electrical system. It is also possible that the tachometer cable is loose, damaged, or disconnected.
It's recommendable to take your truck to a professional mechanic to diagnose and fix the problem. In some cases, the problem might be fixable by replacing the sensor or cable, but in other cases, it may require more extensive repairs or replacement of the tachometer itself.
It's also important to note that even though the tachometer is not working properly, it does not affect the performance of the engine, but it will give you a wrong idea of the RPM, which could lead you to over-rev the engine and cause damage.

The first thing you do is check for system fault codes, then if no joy check the fuel pressure next.

Its either the tach censer or the wire that its connected with. Sometimes the connection on the back of the tach gets coroded, try cleaning that first, then check the wires on the back of the tach. If all is well you might need a tach censer.

The speedometer and tachometer problem on your Trailblazer instrument cluster is very common on the 03-06 models. It's caused by failing stepper motors on the cluster's circuit board and can be fixed. Check out this page for more on how to get it fixed - Trailblazer tachometer problems

Same exact issue with 99 Windstar...is it the alternator, contacts in cluster or what. Checked the fuse and all was good. Anyone have any ideas?

Not sure about the tach, but the link should give you ideas to check on.
Do It Yourself Diagnosis and Repair

Common issue with the 04-05 Impala instrument clusters. It's caused by a failing stepper motor on the cluster's circuit board behind the tachometer but it can be fixed. Check this page for more about it and how to get it fixed - Impala tachometer does not work

Check wires from battery to starter motor and altinator are clean and tight.If they are ok i would change the starter motor.

the dash voltage egulator probably went bad. First,check the battery & make sure you have 12 volts,not running. Check it again running & you should see about 14.5 volts. If that's good,I'd replace the guage assembly.

On the 03-06 Trailblazer instrument clusters this is a common problem. It's caused by a failing stepper motor on the cluster's circuit board and can be repaired. Check out this page for more about how to get it fixed and other common cluster problems with the Trailblazers - Trailblazer tachometer broken