A friend of mine just had his u joints replaced in his half shaft passenger side of an 89 coupe, He got it back and now his speedo and tach jump around. Is there anything they might have damaged during his u joint replacement to cause this?

Thanks

 

ttt

 

You never know - tach signal is from the distributor, through the tach filter to Pin C5 on the Dash Connector - hard to imagine how that wire got disturbed. Speedo is from the VSS on the tranny to Pins D11 & C15, so you might want to check the connector at the tranny - if cruise doesn't operate this is a good suspect. More than likely, this sounds like an intermittent ground or a bad display. Check ground Pin D3 which runs to the ambient overide switch and then out through the ECM harness (passenger side of the engine) to the block below the driver's side valve cover. That ground is spliced into most of the ECM driven sensors, so if the motor is running good, an open is probably very close to dash or maybe it got disconnected at the ambient switch above the brake pedal. The other dash ground is from Connector Pin D1 to the left footwell behind the carpet. It too is spliced into a host of other grounds, so if everything else is working ok, check close to or at the dash. Prior to '89, these grounds took a somewhat different path and the trick was to simply solder them together at the dash (assuming if one was still good, problem solved). You can still try that though if you bypass the ambient temp switch, cruise will operate below freezing temps.

 

Thanks, I'll let him know :cheers: