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DIY Automotive Resource

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Q.   Why is my fuel gauge not working? 

A.   The most common problem is the circuitry is not complete.
       To test this out, use a voltmeter and check the continuity on wires going to the fuel sender. Next,
      disconnect the wire from the Fuel Gauge and check for continuity to the ground.

 Q.   Why is my tachometer jumping?

 A.   Check:

  • Is your ground on the engine block? And NOT NEAR THE ALTERNATOR?
  • Is your engine grounded to the chassis?
  • Is the body grounded to the chassis?
  • Is your red B+ wire going to the battery, when using the pink wire as key on power?
  • Make sure the Tachometer wire is not near power wires or touching coil.

 Q.   Speedometer

 A.   Check:

  • Black wire goes to where the dash is grounded at the back of engine block.
  • Red wire goes to key on power or same as pink wire.
  • White wire is speedometer output wire and goes to the white wire on the Intellitronix Dash.​

Q.   Speedometer Speed Sensor Wires        

       My Speedometer is bouncing when I rev my engine on my car/truck.  Why is that?

A.   Check:

  • Check ignition key on power and ground source are hooked per the install guide!               
  • If using Intellitronix speed sensor, take the three wires and make a 10 to 12 foot pig tail. Place connector end in a vice. Place all three wires in a drill and twist them together. Use Zip Tie to tie wires every two (2) foot and put them in a wire loom. 
  • Make sure speed sender wires are not running next to any other power wires or spark plug wires.​



For the speedometer in these years you need the wire diagram. GM was not consistent with wire color or pin   location, also they sometimes used what is called a VSS Buffer if this is being used the best place to pick up Speed Signal is the Output side or Factory Speedo wire. The other way is from the ECM/PCM VSS Output Signal wire.


Here is the most common fix to the RF noise problem. Check to make sure you are not using solid core ignition wirer or non-resister spark plugs. When using a HEI Distributor or an Ignition box will also omit high frequency noise. With these you will need a Tachometer Filter a Search for a 75-91 Chevy Tachometer Filter. Click on the link below, this the best one to use. 



We are updating the Circuit Boards here at Intellitronix to make improvements. Some of the power wires may not be correct in Installation Guides. The most common one is on the dashes with one power wire it will be Key On Power Pink or Red.

  • If your dash has Pink and Red, the Pink is Key on power and the Red is going to be constant Power.
  • If you have just Red and No Pink, then the Red wire is Key On Power. 
  • You can always verify the wires by looking at the Board where the wires are. The board is marked by wire position.


If doing a LS engine swap, pick up the Speedometer signal wire from the PCM Pin 50 on the red connector. This is the pin I have found to be right most of the time. To be sure you should find a Pin out Chart to be right. 

If doing a LS engine swap, pick up the tach signal wire from the ECM/ECU and then set the tach switch to 4-cylinders. You may also need to order the Intellitronix LS Engine Swap Adapter Kit – for Series 1, 2 and 3 engines. The part number is 8014LS. If you are getting the tach signal from the ECU, the resistor in the adapter kit will help pull a stronger signal for the tachometer.


N4026 Some of our Tachometer Recall Switches were wired wrong and may have been shipped. The Gray and Green wires are switch. So green goes to coil and gray goes to green tach wire to dash. 


If the fuel tank you are using does not have a baffle around the sending unit is going to move from fuel moving in tank. Since digital is a faster signal unfortunately you are going to see every movement. 


When installing LS Temp sensor bushing. Place Temp sensor in the bushing snugly then install sensor and bushing and crush washer. Tighten bushing to 15 NM then tighten sensor down. 


The Purple wire is looking for a 12V signal, which can come from the head lights or the marker/park lights. This is your preference of when you want the dash to dim. 

This wire cannot be hooked up to the factory switch for dimming. This is a Rheostat which works off resistant this will cause damage to the circuit board.