Reverse Lights

By Jeff Klein

When my 1991 Miata back-up lights failed to light, I pulled out the "15 minute" repair procedure discussed in the Miata Magazine (Winter 1993, pg 48). Having replaced both the alternator and starter motor on my 83 RX-7 GS, I felt eminently qualified for the job.

Looking back on my experience (it took me about an hour, not including the time for the exhaust pipe to cool down) I would like to provide some helpful hints and a little more detail which will allow the task to actually be accomplished in fifteen minutes (see attached).

Procedure for back-up lights switch replacement

According to the 1991 Miata workshop manual (page T-72), there are three failures which could cause the back up lights not to work. The fuse, the bulbs or the switch. Check the fuse and bulbs first.

Tools required: Adjustable wrench (2.5cm), jack/ramp, safety stand.

  1. Lift vehicle in accordance with workshop manual. Use appropriate safety precautions.
  2. Assume appropriate position underneath the car and locate switch (look at new switch so you know what you're looking for).

    Caution: Exhaust pipe may be hot. Since the switch is located very close to the exhaust pipe allow for a 30 to 45 minute cool down period after getting back from the dealer with your new part.

    The switch is located on the top right side of the transmission housing. The hardest part for me was figuring out the best angle of attack. I found I needed both hands (more on that later) to reconnect the wires. If you are using a floor jack like I did, this means getting your chest underneath the transmission housing. Since I am right handed and needed to have my right hand on the same side as the switch, my head was under the engine and my feet under the trunk.

  3. Remove switch housing using adjustable wrench.
  4. Disconnect the wires using a good tug (no need to tag, polarity not important).
  5. Open wiring harness and remove switch assembly. After you disconnect the two wires and un-screw the switch, a wire harness still holds the wires in place (This harness is shown in the exploded view provided in the article). I wound up using a mirror and flashlight to get a good look. The harness is flexible and can be opened up with your finger.
  6. Install new switch using washer from old switch.
  7. Connect wires (polarity not important) I found the only way for me to connect the wires was to reach around the top of the transmission housing with my left hand and hold the female connectors then use my right hand to push in the wires from the switch. I felt the connectors snap into place. This procedure allowed me to connect the wires after installing the switch.
  8. Position wires in wiring harness and push closed.

Note from Ken Stoorza:

I just replaced the backup light switch in my '90 Miata. It had failed some years ago and I finally got around to it.

The articles in discussed making blind connections to the switch leads. I was surprised, as no respectable Japanese engineer would create such a maintenance nightmare. Also, the twisted leads on the old (factory installed) switch suggested there was an easier way. There is.

Simply unscrew the switch, reach up and bend the flexible cable clamp upward, remove all the bundled cable and feed the switch over the top of the transmission. The switch, leads and connectors will be in easy reach on the side of the transmission opposite the switch. Installation is the reverse.

Piece of cake when you do it this way!

Randy Meyer (USVV7W6N@IBMMAIL.COM) details the installation of a reverse lights switch - one of the few failure prone parts on the Miata.

With the help of a few responses, and with having just completed doing it myself, here is the update on installing your own reverse lights switch.

You'll need to get the part from the dealer. The local discount stores don't have this part. I paid about $17.00 for mine. Be sure and specify manual transmission vs. automatic. These instructions are for the 5-speed. I'm not sure if it's identical for automatic or not.

The switch is located on the top side of the transmission, near the tail end of the transmission. It's just about right under the very center of the car, maybe a little to the front, drivers side. You will see plainly the plug-looking switch, with the white caulk material around it. It screws into the transmission, and there are two wires which need to be disconnected and connected.

You'll need to get the car up on the front end, either lift, ramps, jackstands. A lift would cerainly make the job much easier. Once under the car, locate the switch on the tail end of the transmission. I don't think it matters much whether you unscrew the switch first or disconnect the two wires going into the switch. I unscrewed the switch first. You'll need a large open-end wrench. I used an adjustable crescent wrench. The switch will be torqued tightly, but it shouldn't be too difficult to remove. I didn't look at the manual for specs on the torquing, but I'm wildly
guessing that it was in the neighborhood of 15-20 ft-lbs. Once the switch is unscrewed you can disconnect the two wires. Just pull on them until they come out. They are simple plug-in connectors, which just pull straight out to disconnect and push in to re-connect. The only problem with this is that you won't be able to see the wires. They are on top of the transmission and you'll have to feel for the connectors with your hands. It will also be difficult (unless you have a lift) to disconnect and re-connect them because it's difficult to get both of your hands on them. Just pull hard with one hand and they should come loose with no damage done. Now to put in the new switch, once again, I don't think it matters much whether you connect the wires first or screw in the switch first.

I screwed in the new switch first. Then the most difficult part of the whole job is reconnecting the wires. You'll have to use both hands, putting one hand on either side of the transmission from underneath. With one hand hold steady the female connector, and with the other hand push the wire from the switch into the connector. You won't need to push hard, but the hard part is getting them to line up without being able to see them. You'll have to be a little dexterous with your hands to do this. Once you've got them connected, that's it. Total time for me was about 30 minutes max and most of that was spent feeling around the wires getting them lined up.
With a lift, it's probably about a 5 minute job.

From another reader:

My dealership quoted over $100.00 for the switch, so I ordered from NAPA and got my switch in 3 days for about $20.00.

I couldn't get an adjustable wrench in place, but a 15/16" open end works perfectly.

There was no gasket on the original switch or the new one, so I wrapped the threads with Teflon tape and screwed it all the way down snug. Result: the backup lights come on the reverse AND in fifth gear. I had to go back under and unscrew the switch 1/2 turn and it works properly now. We'll see if I get a leak. I recommend you get an o-ring or gasket 1/32" - 1/16" thick to seal the switch and provide the depth for the switch sensor.

Back to the Garage

16 December, 2007