Dash gone wild 454SS

[scottcleaver]

A little back story first. I have a 90 454SS. I changed the dash over to a 91 to get a tach. Repinned and ran tach wire. Everything in new dash works fine. Pull engine for a rebuild. Put together a nice little 454 and decide to run new Holley Sniper EFI. Engine runs fine. No tachometer and no speedometer. All other items in the dash work fine, all warning lights as well as fuel, oil pressure, temp, everything is fine. I pulled the dash module and check my connections on tach wire. Has tach signal. What could have happened? Is the dash or at least the tach and speedo fed via a hot wire or a ground that is sepererate from the rest of the instrument cluster?Thanks Scott

 

[DerekTheGreat]

If I remember right, the speedo is fed by the BRAKE fuse, power goes there, splits to supply the VSS, then goes to the cluster and from there it feeds the ECM. SO you could hook a scanner up to it to see if the ECM is still seeing the speed signal. Has it thrown any codes? Our '88 had rotten connections in the fuse block for that circuit, ECM threw a code as it detected a short or bad VSS. I don't remember if the tach is also fed from the same circuit, I believe it is. That '88 was my first swap and so when I hooked it up I had no speedo or tach, sent it straight to SpecMo in Madison Heights, MI to have them repair it. They put a new tach stepper motor in it but I'm not sure it actually needed it. Tach still didn't work nor did speedo which is what sent me down my rabbit hole until I found that circuit was bad at the fuse block.

 

[Sanctified]

If I remember right, the speedo is fed by the BRAKE fuse, power goes there, splits to supply the VSS, then goes to the cluster and from there it feeds the ECM. SO you could hook a scanner up to it to see if the ECM is still seeing the speed signal. Has it thrown any codes? Our '88 had rotten connections in the fuse block for that circuit, ECM threw a code as it detected a short or bad VSS. I don't remember if the tach is also fed from the same circuit, I believe it is. That '88 was my first swap and so when I hooked it up I had no speedo or tach, sent it straight to SpecMo in Madison Heights, MI to have them repair it. They put a new tach stepper motor in it but I'm not sure it actually needed it. Tach still didn't work nor did speedo which is what sent me down my rabbit hole until I found that circuit was bad at the fuse block.

Can you elaborate on where I can find that circuit?? I have the same issue. I have a 1992 with a TBI to Carb swap on it. All gauges work except Tach and Speedometer.
Thanks.

 

[DerekTheGreat]

My service manual is for the '88 model year, but perhaps it could still help you out. You might still run into an issue or two as they moved to an external DRAC in 1992 and they didn't have a tach in '88 though:

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[Sanctified]

My service manual is for the '88 model year, but perhaps it could still help you out. You might still run into an issue or two as they moved to an external DRAC in 1992 and they didn't have a tach in '88 though:

You must be registered for see images attach

Oh okay. Thank you.