Tachometer only works intermittent and speedometer is inaccurate

[Joe7709]

98 z71 Tachometer can go months without working and then will work for a few days. Speedometer always works but is roughly 8mph off at highway speeds and 4 mph off on city speeds. Everything is stock as well. Any suggestions

 

[Scooterwrench]

A tire size change will make the speedo off. Sounds like an intermittent connection problem with the tach.

 

[Joe7709]

Where is the connection? I pulled the cluster and put it back in so it should be connected to that port well. Tire size is stock

 

[Scooterwrench]

This may help

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Caman96]

Do you have a multi meter? Have you checked tach wire for voltage?

 

[Joe7709]

Which is the tach wire

 

[Caman96]

I think there’s a few different places to access tach wire, but since your tachometer is the issue here, the wire going to your tachometer would be where I’d start. Go to YouTube, got to be a ton of videos.

 

[Scooterwrench]

On 98 the wire is either a white or white with a black tracer where it plugs into the back of the IP. With an analog multimeter set on 12V DC you should see the needle twitching with the engine cranking or running.