Hello, I have a 1985 fiero that the speedo does not work. I baught the car with no gear on the sensor for whatever reason. I have since put in a new sensor I had a gear that is one tooth off that I installed on the sensor. I have checked the current to the plug seems to be OK. I have also checked all fuses. The old 85 mph gauge didn't work so i put in a 120 it doesn't work either. when you crank the car the speedo gauge pops up to zero and when you kill it it drops back down Does anyone have any suggestion.
Posts: 1466 From: Salt Lake, Utah, United States Registered: Oct 2005
You check the connection in the dash. Is it getting a signal? I dont actually know much about how the whole thing works but that is just my two cents. If it is getting something (IE turning on) but not winding up then I would assume that something isnt getting signal, either the ECU or dash connection to the speedo. Check with multimeter.
Posts: 7288 From: Edmonton, AB, Canada Registered: May 2001
You can disconnect the the for the speedo and put a multimeter across the speed wires (should be a yellow and purple) - meter on ac voltage. Now remove the sender from the transmission and spin it with a drill. You should read a couple of volts if working correctly. If you are not reading anything, try connecting the meter directly up to the sensor, if you got something now when spinning it, you will need to check the wiring.
Additionally you can check the continunity of each wire from the speedo to the sensor plug.
NOTE: make sure you check the fuses that they are good as well. The fact that the gage moves to 0 when the key is on indicates power to the gage, but double check all your fuses first.