Speedo Pulse Question - Fixed
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Speedo Pulse Question - Fixed
Do any of the electrical guys know what voltage the speedo pulse for an '81 should be? I'm getting around 6 volts. Should it be 12 volts? I'm trying to track down the problem with my speedometer. Thanks.
Last edited by Boatman; Dec 13, 2011 at 07:30 PM. Reason: Fixed the problem
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I've followed posts describing the sensor circuit. Testing in the spare tire compartment I verified that the switch on the diff was working making and breaking a circuit as the wheels turned. On the central electrical panel I checked voltage at H1 - 12v. At H2 I got a pulse of 6v when the wheels turned. Pulling the dash I followed the circuit paths from the rivets behind the speedo and had 12v at 10r on the right plug (power in) and ground at 7r on the right plug which connects to 11r. Reconnecting the plugs to the cluster I measured a pluse of 6v at the center rivet behind the speedo as I turned the wheels. Everything seems to check out except the pulse is only 6v and I didn't know if 6 is okay or if it should be 12v. If it is supposed to be 12 I'm not sure were I'm getting the loss. Thanks for your help.
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From: Ball Ground, GA
As you found, it is a simple circuit - switched 12 volts. While there are other possibilities, poor connection in the spare tire well and at the instrument pod connectors and foil seem to be the most common problems.
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I followed the great write-up in Dwayne's Garage (thanks Dwayne) and fixed my problem. I cleaned all the contacts and found that I had continuity issues behind the speedo. I soldered all the rivets to the traces, put in all back together and now can tell how fast I'm going. Another problem soved. I'm getting there.
