I swapped out the stock 85mph spedo cluster in my 86 RS for a cluster out of a 88 with 110mph speedo and 5500rpm redline tach. all went well, the only problem is the turn signals indicators do not light up when I use the turn signals. I did replace all of the bulbs on back of the cluster before install. they worked on the original cluster..... is there some sort of difference between them??? the only other thing I noticed is that the oil pressure guage on the new cluster reads to 80lbs where the old one read to 60lbs

 

Welcome to TGO. Since electrical gremlins sometimes crop up in "cluster" swaps, I always recommend simply swapping the speedo head (and perhaps in your case, the tach) into your original cluster (if it functioned as designed, which yours apparently did).

JamesC

 

How's your tach functioning so far?

I know, if the Tach's oil pressure gauge says 80 lbs, then you got yourself a V6 tach or cluster. If you take it apart to swap the speedo or whatever, you might find a small tag that states a set of numbers, then the CYL part will state 6 to confirm.

I bought a V8 tach on eBay for my Sport coupe and half of the cluster doesn't light up and turn signal indicators are dead, the circuit board on the back usually is at fault.

My only suggestion is look for another instrument panel

 

yeah. I kind of figured it out today. drove the car...... and to my delight my little 305 buried a 7000RPM tach.... how awesome is that? Oh well live nad learn. got the piece from a local yard for $20. can't complain. used to be into Mustang's ...... learning something new
thanks

 

As JamesC said swap the new gauges into your original housing and reinstall it. Should fix that pesky light problem.