Instrument pack My '97 900 SE Turbo instrument pack (speedometer, tachometer, etc.) will go completely dead for less than a second while driving, then restart as if I had just turned the car on.  It does not affect any other systems and the car continues to run as if nothing happened.  Any ideas?

Speedometer
The instrument cluster receives the vehicle speed sensor (VSS) signal from the PCM through the SCP communication network. The instrument cluster micro-processor monitors the VSS input from the PCM and commands the speedometer with a corresponding movement of the pointer.

Tachometer
The instrument cluster receives the tachometer data from the PCM through the SCP network and commands the tachometer according to the data.

Taking your vehicle to a qualified repair shop that has diagnostic tool to scan the instrument cluster for DTC'S - diagnostic trouble codes an also view sensor input data to the PCM engine computer an the I/C would be your best bet .

Sorry but it's not a fuse problem . There is not a fuse just for the speedometer . The microprocessor inside the instrument cluster determines where the speedometer needle points , just like the fuel gauge , tachometer etc... Having the vehicle checked for DTC'S would be the proper step to take .
Vehicle Speed Signal
The vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4-wheel anti-lock brake system (4WABS) module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems which require a vehicle speed signal input.
Speedometer
The electronic speedometer receives a speed signal from the 4WABS module.

• The Speedometer/Odometer Is Inoperative

• Circuitry.
• Speedometer.

• GO to Pinpoint Test E .

No where in this factory diagnostic step does it say to check a fuse !

PINPOINT TEST E: THE SPEEDOMETER/ODOMETER IS INOPERATIVE CONDITIONS DETAILS/RESULTS/ACTIONS E1 CHECK THE VOLTAGE TO THE INSTRUMENT CLUSTER
Instrument Cluster
Measure the voltage between instrument cluster C288-7, circuit 1001 (WH/YE), and ground.

• Is the voltage greater than 10 volts?

Yes GO to E2 .

No REPAIR circuit 1001 (WH/YE). TEST the system for normal operation.
E2 CHECK THE INSTRUMENT CLUSTER PRINTED CIRCUIT
Instrument Cluster
NOTE: Measurements must be made to the speedometer gauge pins that are inside the instrument cluster printed circuit clips.

Measure the resistance between the speedometer pins (which can be seen in the middle of the instrument cluster printed circuit clips) and the corresponding instrument cluster terminal. Refer to the table for the pin and terminal assignments.

Instrument Cluster Terminal Speedometer Gauge Pin C286-13 C287-1 S C287-2 G C288-7 BATT
.

• Are the resistances less than 1 ohm?

Yes GO to E3 .

No INSTALL a new instrument cluster printed circuit. REFER to Instrument Cluster Printed Circuit . TEST the system for normal operation.
Your best bet , take it to a qualified repair shop

The speedometer is operated differently then the tachometer. Tachometer
The tachometer displays the engine speed in revolutions per minute (RPM). Voltage pulses are taken from the ignition control module (ICM) (Gasoline) or the generator (Diesel) and sent to the tachometer. Solid state circuits convert the pulse frequency in order to move the pointer of the tachometer.

Tachometer Inoperative (Gas)
Step
Action
Value(s)
Yes
No
1
Did you perform the OBD II System Check been performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check (5.0L/5.7L); Powertrain On Board Diagnostic (OBD) System Check (7.4L)
2
Remove the I/P Cluster.
Disconnect the Ignition Coil connector.
Connect a J 39200 DMM (continuity) between I/P Cluster connector cavity 6 and ground.
Is continuity present?
--
Go to Step 3
Go to Step 4
3
Locate and repair the short to ground in CKT 121 (WHT) between the Ignition Coil and the I/P cluster. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
--
Refer to Instrument Cluster System Check
--
4
Connect a J 39200 DMM (continuity) from I/P Cluster cavity 6 to ignition coil connector cavity B.
Is continuity present?
--
Go to Step 5
Go to Step 6
5
Replace the I/P Cluster. Refer to Instrument Cluster Replacement .
Is the repair complete?
--
Refer to Instrument Cluster System Check
--
6
Locate and repair the open in CKT 121 (WHT) between the Ignition Coil and the I/P Cluster. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
--
Refer to Instrument Cluster System Check

Two things. The ground wire from the cluster is loose or the power wire to the cluster may be loose at the connector.

new alternator

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Check the connections on the back of the instrument cluster. It sounds like you have a faulty instrument cluster board, a poor connection and perhaps, but less likely, an ECU issue.

Hi Norton,

What has happened is your speedometer and tachometer drive motors are failing inside your silverado instrument cluster. I see this very often in GM trucks, to fix the problem you need to have your instrument cluster rebuilt.

Check out this article that talks more about it http://drspeedometer.com/chevy-silverado-instrument-clusters-why-they-quite-working

Thanks,
Fred

Pretty common problem with these. Here's a guide to learn how to fix GM instrument clusters yourself, I used it to fix mine and it worked great.How to guide for Silverado instrument cluster repair
Pretty common problem with these. Here's a guide to learn how to fix GM instrument clusters yourself, I used it to fix mine and it worked great.How to guide for Impala instrument cluster repair

there is a wiring package that contains a wiring connector for the back of the cluster.the part number is 5016261aa