Dandxj Posted February 17 Share Posted February 17 1990 4.0L Renix AW-4 At idle the tach in the dash reads 500 RPM in park. This seemed low so I plugged in a handheld tach into the diagnostic terminal next to the relay center and it was reading 950 RPM. What would cause the difference? Is the 1990 tach adjustable? TIA Link to comment Share on other sites More sharing options...
89 MJ Posted February 17 Share Posted February 17 Seems like there should be a knob for adjusting it. It’s mentioned a little bit here: Link to comment Share on other sites More sharing options...
Dandxj Posted Friday at 05:15 AM Author Share Posted Friday at 05:15 AM Thanks for the info. Does anyone have a photo of the adjustment "knob" or will it be obvious when the tach is out of the dash? Any ideas what would cause the tach to drift ? It is original to the truck and was "accurate" in the past. Link to comment Share on other sites More sharing options...
fiatslug87 Posted Friday at 06:31 AM Share Posted Friday at 06:31 AM Link to comment Share on other sites More sharing options...
Dandxj Posted Saturday at 05:55 AM Author Share Posted Saturday at 05:55 AM Thank you very much for the photo. Now I know what I am looking for. I do not suppose there is an easy way to adjust without removing the cluster, make adjustment, reinstall cluster, verify RPMs, repeat as needed. Link to comment Share on other sites More sharing options...
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