Gauge Face Replacement

Last updated: March 27, 2001

Date: Wed, 14 Mar 2001 15:22:11 EST
Subject: (rx7) [3] swaping gauge faces and calibrating instruments

Hey guys I just swaped the faces on my gauges. It is not easy.

I very carefully removed the instrument hood and then separated the gauges. The actual gauge assembly is a pain to get apart. The whole thing snaps together and is difficult to take apart.

The gauges are screwed in from the back side and all the screws need to come out. I was very nervous taking the needles off. This time I made a note of where they were so it would be right when I put it back together.

I did this with the speedo by turning it all the way clockwise untill it came to a stop. I found it lined up exactly with the 6 where 60 is written on the bottom right of the face. If you do this make sure you don't force the needle past where it stops. I popped the needle off by grasping the base with one hand on the long side, and then very gently pying it up with a small flat screwdriver on the other side. Grasp it by the orange needle, not the black center because it will crack.

The face of the speedometer was glued on so I very carefully pealed it off and helped it up by prying around with the small flat screwdriver.

Next I put the new gauge face on and secured it with a drop of glue. The tachometer face secures with tiny pop rivets.

I then put the needles back on in the same positions they were when I removed them.

I left the oil pressure, temperature, and fuel faces alone because they are the same for all rx-7s.

I screwed all the guages back to the assembly and temporarily hooked them up. The tach, temperature, and oil presure seam to be working right.

The speedometer also works but I want to make sure it is still calibrated properly because I had to take the needle off. How would I do this? I just drove around the block side by side with my sister. I had her go 20mph, 35, and 30 and my speedometer was showing the same so I think it is right.


Date: Tue, 13 Mar 2001 18:07:16
From: "Mike Putnam" (

    >I have my gauges apart so that I can swap the instrument faces from my 93
    >into the 94 (I like the 93 finish with more tick marks
    >better) and to swap tachometers (buzzing noise when rpm's drop) I
    >already pulled the needles off the tach and speedo and then
    >something came across my mind.

Holy Sh%t, don't remove the gauge needles!! While working on improving the temperature and oil pressure gauges I have completely disassembled several instrument gauges. I have found that removing the needle from the gauge is death for the gauge about 50% of the time. If the needle came out with the metal pin attached you're probably screwed. It is very difficult to get every thing lined up (the pin acts as an axel that keeps all the little pieces together). Even if you get everything aligned and the pin back in the needle usually doesn't move as smoothly as it originally did.

    >Does it matter where the gauge is when you put the needle back on?


    >Would this throw off the calibration?


    >I am also going to do the water temp mod while I'm at it.

Good idea, but you may still be up the creek.

    >How do I make sure the gauges will read right when I put them back in?

For the small gauges you need:

  1. A power supply (or use the battery)
  2. A ohm meter
  3. A potentiometer 0-100 ohms.

Reassemble the small gauge except for the needle. On the back of the gauge there are three brass screws, power signal and ground. See the crude diagram below.

                  X   signal

       X ground               X power

Attach the power supply to the power screw, ground to the power supply ground, and the pre-adjusted potentiometer to the signal and the other end to power supply ground. You need to adjust the potentiometer to a known sensor resistance value. For example, if memory serves me right, with the oil pressure gauge 26 ohms is 60psi, 10 ohms is 120 psi. Dial in 26 ohms and push the needle on so it is pointing to the 60 mark. Then readjust the potentiometer to 10 ohms the needle should move to the 120 psi mark. Cycle the potentiometer between 10 and 26 ohms several times if the needle doesn't move to the proper mark each time the gauge is unreliable and shouldn't be used. I haven't messed with the speedometer or tach so I profess ignorance on how to go about adjusting them.


Also see: Dash Removal

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