Installing Electronic Gauges - MR2 Owners Club Message Board
 
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post #1 of 15 (permalink) Old April 4th, 2019, 01:36 Thread Starter
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Installing Electronic Gauges

Whats up ya’ll? This is how I installed my two aftermarket electronic temperature gauges. Keep in mind you have several options for how to go about this but I stuck to the basics. This thread is assuming your are going with the aftermarket gauges that require you to cut into one of the coolant hoses.

Tools needed:
  • Aftermarket temperature gauge of your choice, with power harness, and sensor harness.
  • 32 mm water sensor adapter
  • Coolant hose clamps if your adapter does not come with them
  • A sharpie
  • A sharp pocket knife or something to cut coolant hoses with
  • Teflon tape
  • Wire connectors suitable for crimping
  • Wire cutters, crimp tool, etc
  • Wrench and socket set
  • Drill
  • Rubber grommet
  • screwdriver

Optional tools:
  • Electric tape
  • High temperature tape
  • Plastic flex tubing
  • Zip ties
  • Coolant
  • Drain pan
  • Screws
  • Hose supports
  • Car Jack
  • Expandable circuits aka (“piggy backs”)

Before I begin I would like to say that this is not a difficult job. However, you should not do this if you do not plan on bleeding the MR2 cooling system afterwards. This job will most likely require you to bleed the coolant system. If you own an MR2 you should know that bleeding the coolant system is no fun. Also, keep in mind that I did this how I felt was best but I’m sure there are better options out there.

Please do not comment until I finish this DIY guide.
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post #2 of 15 (permalink) Old April 4th, 2019, 01:46 Thread Starter
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Step 1

The Presetup

Locate the hose where you want to install the adapter that will hold your new temperature sensor. All MR2 hoses have a diameter of 32mm but not all hoses are ideal. In a normal car you only have two hoses so deciding which hose to cut into is relatively simple. Ideally, you want to install the adapter into the hose that is receiving the coolant that is exiting your engine. This is known as “the upper radiator hose”.

The upper radiator hose reads the hot temperature that is exiting the engine and so installing the adapter is ideal here. Why? Because the new sensor sits within the adapter, the adapter sits within the upper radiator hose, and therefore will read the temperature of the coolant as soon as it exits the engine. Meaning, that if there is an overheating problem you will know IMMEDIATELY.

The problem with the MR2 is that we technically don’t have a traditional “upper” and “lower” radiator hose. Instead we have 8 coolant hoses due to the mid-engine setup. Regardless, the theory is still the same here. We want to tap into the hose that reads the temperature of the coolant exiting the engine. You technically have 4 hose options here but I personally feel that only one of the options is best.
  • Option 1: Long C shaped hose the connects to the water neck
  • Option 2: Short S shaped hose that sits near the shifter cables
  • Option 3: L shaped hose that sits under the front of the car
  • Option 4: Short hose that attaches to the radiator located in the frunk

Options 2-4 are not ideal if you know anything about the MR2 cooling system. These hoses are not only complex shaped but they are located in bad areas. You will go through lots of trouble simply trying to make it work. I chose option one because it is a long hose and as I mentioned it directly takes the water that is exiting the engine. Below is a picture of the hose that I chose.
Attached Images
File Type: jpg IMG_6053.jpg (1.08 MB, 8 views)

Last edited by MR2ManiacJC; April 4th, 2019 at 02:13.
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post #3 of 15 (permalink) Old April 4th, 2019, 01:54 Thread Starter
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Step 2

Draining the coolant

Find a way to drain a bit of the coolant. You only need to drain enough so that there is no more coolant in the C shaped hose. Because the C shaped hose sits really high it will start losing coolant as soon as the coolant level drops from draining. I chose to drain the coolant from the drain plug that sits directly under the car. Only open the driver side plug.

This is where you will use a 12mm socket and possibly a jack if you can’t fit your arm down there. In my picture you will notice that I have both drivers side and passenger side drain plugs open. I had to do this because I installed two temp gauges. However, if you are only installing one simply use the drivers side drain plug. I drained about a gallon of coolant but you may only need half a gallon or so.



Protip: After you open the drain plug coolant will flow slowly but it will stop draining after a few seconds. Go to the back of the car and remove your radiator cap. Make sure that your drain pan is sitting slightly towards the passenger side of the car because removing the radiator cap will force the coolant to point in that direction as it drains. After removing enough coolant put the radiator cap back on so that coolant no longer flows. Then reinsert the drain plug with your 12 mm socket. You will no longer need to drain at this point.
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Last edited by MR2ManiacJC; April 4th, 2019 at 02:13.
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post #4 of 15 (permalink) Old April 4th, 2019, 02:01 Thread Starter
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Step 3

Installing the adapter

Locate a part of the hose that is relatively straight. This will make it easier to install the adapter successfully. Place your adapter over the part of the hose that you have selected. Using your sharpie trace the outline of the adapter so that you know how much you have to cut off. After your measurements have been done either remove the hose so that you can make your cut or cut leave it in place and cut it from there. I chose to leave it in place when cutting.

Picture of measurements:
IMG_6056.jpg

After you have cut the hose check to see if you have cut enough. Temporarily install the adapter so that you can see if it flows with the shape of the hose. Basically just make sure it doesn’t force the hose into any weird bend that may cause problems. If you are happy with the setup wrap some teflon tape around your new temperature sensor(mine came with my gauge) and then insert the sensor into the adapter. Once that is taken care of, insert the adapter with sender into the hose and tighten the clamps down.

Picture of adapter and sensor installed:
IMG_6057.jpg

Last edited by MR2ManiacJC; April 4th, 2019 at 02:13.
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post #5 of 15 (permalink) Old April 4th, 2019, 02:09 Thread Starter
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Step 4

Preparations before routing the sensor harness

Disconnect your negative battery cable so that your car doesn’t die. After that you can go inside the car and remove your shift knob, shift boot, required trim, and center console(armrest). The shift knob simply twists off, the shift boot unclicks as well as the trim, and the center console is only held by 4 screws.

Picture of center console removed:
IMG_6058.jpg


After removing the console you can proceed to drilling a hole from inside to the back of the car. Ideally I would have preferred to drill a hole from outside to inside but there was no clearance. PLEASE be VERY CAREFUL when drilling the hole. You do not need a lot of force because the metal is thin. Little by little press on the drill until you can puncture through.

Picture of half inch drilled hole:
IMG_6059.jpg

Do not drill aggressively and then later find out you drilled a hole into your fuel lines or something. The size of the hole you drill is up to you. I drilled one that was big enough for the harness to run through without squeezing it. After drilling the hole insert a rubber grommet so that you do not cut the wire when routing it through.

Picture of routed sensor harness:
IMG_6061.jpg

Last edited by MR2ManiacJC; April 4th, 2019 at 02:12.
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post #6 of 15 (permalink) Old April 4th, 2019, 02:26 Thread Starter
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Optional part of step 4

Optional

Because I am a perfectionist, I went out of my way to make this look OEM and safe. I bought some high temperature tape to wrap the harness in and then placed it inside some flex tubing. I am really happy with the outcome and definitely recommend because the harness sits near fuel lines and other hot components. Keep in mind that I ran two harnesses and two gauges which is why I end up with two sensor connectors and two flex tubing hoses. You will only have one.

Picture of tubing routed:
IMG_6064.jpg
Attached Images
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File Type: png IMG_6063.PNG (2.18 MB, 5 views)
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post #7 of 15 (permalink) Old April 4th, 2019, 12:26 Thread Starter
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Step 5

Cleaning things up

I suppose this step could also be optional but I would not avoid doing this. I went and bought some hose clamps with the same diameter as the flex tubing. I then took my drill and used a mid size bolt to drill the clamp against the firewall of the car. This way the flex tubing that holds your harness is not dangling all over the place. Essentially, after this you are done in the rear until it is time to bleed the cooling system. Below is the finished product.

IMG_6089.jpg


Looks pretty OEM if you ask me.
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post #8 of 15 (permalink) Old April 4th, 2019, 12:44 Thread Starter
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Step 6

Routing the power harness


This step is assuming that you will be using expandable circuits aka “piggy backs” as I did to wire the gauges. Basically if you are using expandable circuits you want to remove your center trim that holds the stereo and the bottom trim that sits below your steering wheel. The location of your gauge pod will affect the route you must take. I am using an ashtray gauge pod purchased from Camposites. It works great if you don’t mind giving up your ashtray/holder.

Therefore, I unscrewed my AC unit and slightly pulled it forward so that I could pass my harness through there. I then directed the harness towards the steering wheel and passed it below. It sits next to all the wires that are also under there. Keep in mind that the goal of using an expandable circuit is to tap into your fuse box rather than into your wires. Whatever route you take for your power harness must always end at the fuse box that sits near the clutch pedal if you are using expandable circuits.

I can’t really tell you which way to route your power harness because there are several different gauge pods available for our platforms. So depending on gauge pod and location is the route you will take. But once again, if using expandable circuits the power harness should always end at the fuse box to the left of the clutch pedal.
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File Type: png IMG_6092.PNG (2.13 MB, 4 views)
File Type: png IMG_6091.PNG (1.95 MB, 4 views)
File Type: png IMG_6090.PNG (1.84 MB, 4 views)
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post #9 of 15 (permalink) Old April 4th, 2019, 12:52 Thread Starter
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Step 7

Wiring the gauge


I’m not a fan of wiring, let alone cutting into the OEM ignition wiring for the MR2. Therefore, I used expandable circuits. I HIGHLY recommend the use of expandable circuits if you are not good at wiring either. This will easily be a 5 minute job if you use expandable circuits so keep that in mind. I used a MaxTow gauge purchased off the Glowshift website. In the instructions it says to not take power from a stereo or from a dashboard dimmer. Ironically, I had thought of doing that from the beginning so I'm glad I read the instructions haha. But since I couldn’t I decided to go with expandable circuits.

The logic is simple for expandable circuits. Crimp the wires from your gauge power harness that will receive 12v power into individual expandable circuits. For example, crimp the red cable onto one expandable circuit, crimp the white onto another, and so on. DO NOT CRIMP YOUR GROUND ONTO AN EXPANDABLE CIRCUIT. Instead, crimp the ground onto a terminal connector if it didn’t already come with one.

Below is a picture of my gauge wires crimped onto the expandable circuits. The reason why I have two reds, whites, and oranges is because I had two gauges. You can run up to 4 gauges into a single expandable circuit as long as the power sources are the same.

IMG_6096.jpg
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post #10 of 15 (permalink) Old April 4th, 2019, 13:03 Thread Starter
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Step 7 Continued

The red wire

After you have crimped, go ahead and connect your negative battery terminal again. If you have a test probe you can use it here or you can use a multimeter like I did. The gauge you go with will determine the amount of wires you have. My gauge had only 4: a Red (unswitched constant 12v), a White (switched 12v), a Black (ground), and an optional Orange (switched 12v that receives power from the headlight fuse).

Assuming your gauge is similar to mine . . . for the Red you want to locate a constant 12V source that receives constant 12 volts while the car is off. Therefore, run your probe or multimeter and touch the top terminals of every fuse until you find one that reads 12V. For me this was a 30 amp fuse. Once located, you remove that fuse and place it onto your expandable circuit. Your expandable circuit should have came with a separate 4 amp fuse which you must add to the second slot of the expandable circuit. You will notice each expandable circuit has two slots: one to insert the fuse you will remove from your car and another for the 4 amp fuse that your circuit comes with.
exp.JPG
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post #11 of 15 (permalink) Old April 4th, 2019, 13:15 Thread Starter
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Step 7 Continued x2

The white wire

Again, assuming your gauge harness is similar to mine . . . for the White wire we have to locate a 12V power source that is switched when the ignition is set to on or off. Therefore, have a buddy turn the key to the on position as you locate for a fuse that has 12V when ignition is set to on. Note: this fuse should read 0V when the ignition is turned back off. For me this was a 15 Amp fuse. Below is a picture of the expandable circuits for the Red and White installed into the fuse box. Yours should look very similar.
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post #12 of 15 (permalink) Old April 4th, 2019, 13:24 Thread Starter
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Step 7 Continued x3

The black wire

For the Black, attach a ground terminal if you haven’t already. Locate a good reliable ground source that is unpainted. Luckily for us there is a threaded hole which sits extremely close to the fuse box. I simply found a bolt to match the thread size and tightened the ground terminal with it.

Picture of bolted down black wire with ground terminal
Ground.jpg

If your gauge is anything like mine you are technically done here. You should be able to turn the key to the on position and see your gauges light up. This is assuming you only have 4 wires in your gauge power harness. The Orange wire is optional and does not affect gauge function.
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post #13 of 15 (permalink) Old April 4th, 2019, 13:31 Thread Starter
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Step 8

Optional orange wire

You probably noticed that the brightness of the gauge is very bright at night. You can either manually dim it yourself if your gauge is equipped with a dimming button OR you can connect the orange wire expandable circuit into the fuse box located in the frunk. You need to locate a fuse that receives 12V power when the headlights are turned on aka the 15 amp fuse for either your Left headlight or Right headlight. Either of these two fuses will work. However, you will need to purchase additional AWG wire so that you can extend your orange wires to the frunk. I used a 16 gauge AWG wire.

After doing so your fuse box will not longer fully close which kind of sucks. However, whenever you turn your headlights on the gauges should automatically dim on their own which is cool. Note: inside the frunk fuse box I wrapped my wire in high temperature tape because it sits really close to the relays which tend to get hot.

Route from drivers side fuse box to fuse box at frunk

r1.jpg
r2.jpg
r3.jpg
r4.jpg
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post #14 of 15 (permalink) Old April 4th, 2019, 13:35 Thread Starter
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Step 9

Finishing the job

At this point I would zip tie or find a way to keep your wiring from falling to your feet. You should also reinstall your trim if you haven't already. Make sure to tighten down any hose clamps you may have loosened before adding coolant. Also, make sure the sensor has teflon tape. After that, you can basically begin adding coolant once again and be ready to bleed the system of air.
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post #15 of 15 (permalink) Old April 4th, 2019, 13:40 Thread Starter
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Done

You are officially done!
Hope you guys enjoyed this thread and please leave any comments or questions you may have.

Thanks for reading!




Also, my apologies for the small sized pictures. This forum always shrinks them. I've seen other members post pictures that are enormous but I can never seem to do that. If anybody is kind enough to share the secret, please do. I'd like to make theses pictures larger.
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