Do i need to replace a fuse when the speedometer stops working on 1988 grand marquis?

It's *possible* a blown fuse is the reason your 1988 Grand Marquis speedometer stopped working, but it's not the most likely cause. Speedometers in that era often rely on a cable driven mechanism, not electronic signals heavily dependent on fuses. A more likely culprit is a problem with:

* The speedometer cable: This is the most common cause. It can break, fray, or become disconnected at either the transmission or the speedometer itself.

* The speedometer itself: The instrument cluster might have an internal issue.

* The speed sensor (if equipped): Some late-model 1988s might have a rudimentary electronic speed sensor, but it's less likely. A faulty sensor is more common on later model cars.

Therefore, while you *should* check your fuses (consult your owner's manual for the correct fuse for the instrument cluster or gauges), don't expect that to solve the problem. Start by inspecting the speedometer cable. This usually involves accessing it under the dash and at the transmission. A broken or disconnected cable is visually apparent.