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Old 07-19-2012, 06:03 AM   #1
02CWRX
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Default Version 7 JDM STi Cluster Outside Air Temperature Sensor

I had posted links to this around here, but since then, the site it was on went down so I decided to repost it here because there seemed to be some interest in it. Be forewarned though, this is really long.

So, I have a 2002 WRX, and my gauge cluster is a version 7 STi cluster. At the time when I originally did this (2010) everything I found said that making the V7 OAT work hadn’t been done yet, or people asking how to do it. I found a write up on a few sites by the same person about installing the OAT sensor in cars that are using a version 8 cluster. The V7 and V8 clusters are pretty different though. To start, the version 7 cluster has incandescent lighting, and electromechanical gauges (but they’re not stepper motor controlled like the V8 cluster), and the V7 cluster also is missing the DCCD displays (except for a rarer version which does have it). The version 8 cluster has stepper motor control gauges, LED lighting, does the opening ceremony sweep on key-on, has the DCCD display with internal CPU for display, etc. When installing the version 8 cluster, the wiring for the gauge lighting (dimming) is known to be an issue, as is a wire which needs to be cut when installing the cluster in certain chassis because it causes fuses to blow, and something about an ABS light working backwards. This all confirmed my concern that the wiring would be different in the clusters seeing as the version 7 cluster is direct plug and play in the 2002 chassis. So, I looked into it on my own.

I got my hands on some wiring diagrams for a US model 2002 Impreza Outback Sport, which happens to have the OAT sensor and display stock. The theory was the wiring diagrams for the chassis and gauge cluster pin outs should be the same, seeing as they were both 2002 Imprezas. As it turned out, they mostly are. The wiring diagrams specify a 5 volt signal which is needed to “activate” the OAT circuit, which the write-up for the version 8 cluster also speaks of. It also shows the pin outs for the inputs of the OAT sensor, in-line resistor, etc. All which are mentioned in the how-to for the version 8 cluster. What I did, was I took what I knew about the USDM Outback Sport wiring, and combined it with the how-to information, and came up with my own circuit and implementation.

Assembling the regulator:

Now, to accomplish this, you need the same supplies as the version 8 how to which consists of:

• OEM Subaru OAT sensor (PN 73730FE010)
• Spare gauge cluster pin with a few inches of wiring attached
• 5 volt regulator (Radio Shack PN 276-1770)
• Watt 2.2K Ohm resistor (Radio Shack PN 271-1325)
• Misc electrical connectors as needed
• Lengths of 16 gauge wire or so in colors of your choice. You need enough to build the circuit, but also run from behind the cluster area to the front of the car where the sensor mounts. I used red, black, blue, and yellow.

Tools you will need:

• Phillips screwdriver
• Wire cutting/stripping/crimping tools
• Electrical multi meter or a volt/ohm meter
• Soldering iron with solder
• Heat shrink tubing

First, remove the gauge cluster from the car. I wont touch on this too much since you most likely swapped clusters already and just want the OAT gauge to work. In simple form however, remove the two phillips screws at the top of the cluster surround, lower the steering wheel, and pop it out of there. Next, pull the 3 phillips screws holding the cluster into the car. Pull the bottom of the cluster towards you so you can reach behind and unplug the three harnesses across the back. Once thats done, set the cluster off to the side for now.

To get started, we need to assemble the 5 volt regulator circuit. It’s basically the same as the version 8 how-to, but then again, it’s a 5 volt regulator, it’s a simple concept. There's an input, a ground, and an output, haha. There is a diagram on the back of the package which comes in identifying the leads, so let’s get started.

Here is the regulator:



First we will solder a wire to the input lead. This is what you will connect to a 12 volt source:



Solder a wire to the ground. Obviously, you will ground this wire:



Solder a wire and also one end of your 2.2K ohm resistor to the output lead of the regulator:



Solder one last wire on the empty lead of the resistor:



When the regulator sees 12 volts across the input and ground, it regulates an approximate 5 volt output on the output lead. This is what we are going for. Now, hook the positive and negative wires up to a power source and make sure you are getting about 5 volts out the output lead using the volt meter. If you do, you wired it up correctly. If you get 12 volts, you need to reverse the positive and negative leads. For fun, you can also check the output of the 5 volt lead through the resistor and see the difference between the resisted voltage and non-resisted.

Once you know the circuit works, go ahead and heat shrink over all your soldered wires and clean it all up as seen in the pictures below. I chose to heat shrink the individual wires, then all together for strength:





You should now have a regulator with 4 wires - a positive, ground, non-resisted output, and a resisted output. I chose red for positive, black for ground, blue for non-resisted, and yellow for resisted. Color choices are up to you, it’s just what I had handy:



Installing the regulator:

The first step is supplying the CPU with 5 volts to operate. To do this, we need to wire the output of our circuit to the B12 pin of the gauge cluster, which is missing a pin in the center plug. Solder the non-resisted output wire to your spare cluster pin and install into the B12 position.

The second step is supplying the CPU inside the cluster with a resisted power source on the B11 pin, and at the same time, we need to get this same voltage into one side of the OAT sensor. This wire is the voltage the CPU will compare to the resisted voltage of the OAT sensor. I chose to run the wire from the resistor, to the gauge cluster plug, then from the plug to the OAT sensor.

So, take your resisted output wire and either tap into or cut the B11 wire on the chassis side of the cluster harness. If you choose to cut it, the resisted output wire needs to connect to the plug side of the cut wire, not the chassis side. Thus the voltage would be going into the cluster, not the car. I personally chose to simply tap into this rather than cutting it by back probing the wire into the connector.

The last thing to do would be to run one more wire from the other terminal of the OAT sensor back to the gauge cluster pin B8. Again, I chose to back probe the wire into the cluster plug rather than cutting anything. Here's what I ended up with after it was all done:



The version 8 how-to talks about pin B28 – "version 7 cluster in a bugeye" people can ignore this pin. It doesn’t have the same problem when the version 7 cluster is installed in an 02/03 chassis. Just leave it as is.

At this point you should have everything wired up except the power for the regulator and the ground for the regulator. What I chose to do was find a switched positive wire in the cluster wiring, as well as a ground for my regulator circuit. This way the circuit only sees power when the key is turned on. I found a power lead in the plug to the right (as you are facing the dash as if you were driving), and I found a ground in the plug to the left. I don’t have the pin numbers right now, but they are easy to find with your meter, any 12V power and ground will work, it doesn't even have to be in the cluster wiring. I just chose it for simplicity and convenience. For both the power and ground, I again back probed into the plug as to not cut/disturb anything. The circuit draws such a small amount of power/current there should be no problems drawing a small amount of power from the cluster harnesses to power the regulator.

Testing the operation:


Once you have the power and ground wired up, go ahead and install the cluster back into the dash and turn the key on. You should see a temp display on the gauge - something like 40 or 50 degrees Celsius is what I was seeing on initial power up I think, but its possible it will give you an "actual" reading. If you get the same dashes you used to see, give it a second, but if nothing comes up, you need to check all your wiring. It should give you a number fairly quick if it's done right.

The ambient temperature CPU has a few processing routines which we need to overcome to test the circuit. The CPU has a mode which prevents heat soak false readings. To do this, they made it so the sensor will show you a temperature, but it will be the last “known” temperature until the car moves over 0.3 KM at over 10 KM/H (or so). When stopped and running, I believe that live readings again stop until the car moves again. When you shut the engine off completely for parking and return to the car later, the gauge does one of two things. If it has been LESS than approximately one hour, the cluster will show you the last temperature known before turning the key off and go back into its routine of live/static data. If it’s been MORE than an hour or so, the cluster will show the current ambient temperature when keyed on, but will not show live changes until the car moves under the parameters listed above.

That said, start the engine and take the car for a spin. Alternatively, put the car up on 4 jack stands securely and “drive” the car in place (which is what I was doing to build/test this setup). If the cluster displays 50 degrees Celsius like mine did when first connected, it should change to the correct temperature after meeting the driving parameters listed above. Sometimes it changes rather slow, one degree every few minutes or so, its not typically a “fast” response. I have noticed however that temperature changes going DOWN in temperature are much faster to respond than changes going UP in temperature. Its like the threshold for increasing is higher than for lowering. This hardly bothers me, as I would prefer it to respond quicker when Im driving up a mountain for instance. It will update to freezing temps faster ascending, and would show me still in freezing temps slightly longer descending. Obviously, this is the safer way to go. Im not sure if this action is caused by the circuit, or if the thresholds were purposely programmed like this.

Anyway, after the test drive , the circuit should be working and you should have a functional OAT sensor circuit! To convert from degrees Celsius to Fahrenheit, multiply the temp in Celsius by 1.8 and add 32.

So, to convert 8 degrees Celsius to Fahrenheit it would be:

8 * 1.8 + 32 = 46.4 degrees Fahrenheit



As you can see, my gauge is reading 8 degrees Celsius, and at the time, my thermometer said it was 46 degrees Fahrenheit outside. Pretty accurate! For what it's worth, my gauge has been working since late 2010 when I first did this, and on average, it's within a degree (two at the most) of what is outside.

Hope this helps someone out there.

~T.J.
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Last edited by 02CWRX; 07-19-2012 at 12:33 PM.
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Old 11-08-2012, 10:36 PM   #2
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This write up was super helpful thank you I just got mine working this afternoon. The only difference with mine is that mine is in MPH. Any answers as to how to change the display from Celsius to Fahrenheit? I am perfectly content with Celsius but I'm just curious.
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Old 11-09-2012, 11:59 AM   #3
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Very helpful, ive been hoping to get this figured out on my 04 since im using the same JDM V7 sti cluster. Hopefully ill get a chance to try this and see how it works in the next couple weeks.
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Old 12-21-2012, 12:29 PM   #4
02CWRX
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No easy way to change the actual display from C to F that I am aware of, but a rough estimate to convert is to multiply by 2 and add 32. That at least gets you within a few degrees, haha. Side note, I would LOVE LOVE that MPH cluster. It's a UKDM cluster I'm guessing, I wish I could have found one of those when I was doing my swap.

Glad the write up could help a couple people.

~T.J.
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Old 12-21-2012, 12:34 PM   #5
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Subscribed for winter project
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Old 04-22-2013, 07:13 PM   #6
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Subscibed!
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Old 05-06-2013, 08:11 PM   #7
CAPTAIN1N5ANO
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So 2 of the 3 wire in the odometer harness already have wires in those spots and you only add the one in b12? I just was a little confused because the illustration said the violet ones were added?
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Old 05-07-2013, 02:11 PM   #8
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The guy in the pics chose to insert the wires into the connector directly so he wouldn't have to use vampire tabs for the connections.. There are wires in the existing terminals except for b12.. You can do it his way or splice into the wires if you want, doesn't matter..
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Old 05-08-2013, 03:43 PM   #9
CAPTAIN1N5ANO
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That's what I thought. Just making sure. Is there a trick to getting the plug to release the wires?? Thanks.

Last edited by CAPTAIN1N5ANO; 05-08-2013 at 04:10 PM.
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Old 05-12-2013, 12:19 PM   #10
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There's a lock bar on either side of the connector.. Use a dental pick or an actual wire terminal tool and flip the bar open. Then you just use your pick to pry up the little tab in the terminal and pull the wire out.
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Old 05-14-2013, 07:36 PM   #11
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For those that don't know how to do it
Attached Images
File Type: jpg image-1566721027.jpg (38.7 KB, 87 views)
File Type: jpg image-92564066.jpg (55.0 KB, 84 views)
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Old 07-15-2013, 08:24 AM   #12
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Does anyone here happen to know where I can get a spare cluster pin?
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Old 07-16-2013, 11:26 PM   #13
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If anyone here have they're clusters read outside temp in C and want them to read in F or other way please contact me. Also I can adjust mileage thanks
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Old 07-17-2013, 08:24 AM   #14
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Quote:
Originally Posted by ilarson007 View Post
Does anyone here happen to know where I can get a spare cluster pin?
Got mine a the junkyard, $2. Honda I think uses same aqua color block and pins.

Have a unique problem. Well over a year ago bought a jdm v7 cluster and had a local speed/electronics shop perform the KM to miles on my odo. Installed and worked great...tested against marked miles on interstates.

Recently saw my mpg go from 24-25 mixed up to 30 and latest 39 highway mpg. Too good to be true. Clocked odo against marked highway miles and the odo reads KM.

What happened?

Milinwrx can you reflash so mine accumulates and reads in miles? Can you also do trip A and B to read miles? I know Tacoma Speedo Shop can do the reflash.

Also, followed the OAT install directions on post 1 and mine won't display.
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Old 07-17-2013, 08:58 AM   #15
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Quote:
Originally Posted by malinwrx View Post
If anyone here have they're clusters read outside temp in C and want them to read in F or other way please contact me. Also I can adjust mileage thanks
Quote:
Originally Posted by mhoerath View Post
Got mine a the junkyard, $2. Honda I think uses same aqua color block and pins.

Have a unique problem. Well over a year ago bought a jdm v7 cluster and had a local speed/electronics shop perform the KM to miles on my odo. Installed and worked great...tested against marked miles on interstates.

Recently saw my mpg go from 24-25 mixed up to 30 and latest 39 highway mpg. Too good to be true. Clocked odo against marked highway miles and the odo reads KM.

What happened?

Milinwrx can you reflash so mine accumulates and reads in miles? Can you also do trip A and B to read miles? I know Tacoma Speedo Shop can do the reflash.

Also, followed the OAT install directions on post 1 and mine won't display.
I'm fairly certain it's a programming change in the IC that stores the mileage.

So my other question is, what exactly is the cluster pin? Is that like the entire pigtail so I can get the wires out of it?
i.e.: this piece: http://forums.nasioc.com/forums/atta...3&d=1368574559
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Old 07-17-2013, 09:08 AM   #16
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For anyone having issues with Celsius and Fahrenheit:

This thread talks about what you will need to do:
http://www.rs25.com/forums/f105/t105...pped-dash.html
And, specifically:
http://www.rs25.com/forums/f105/2371352-post35.html
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Old 07-17-2013, 10:40 AM   #17
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Quote:
Originally Posted by ilarson007 View Post

So my other question is, what exactly is the cluster pin? Is that like the entire pigtail so I can get the wires out of it?
i.e.: this piece: http://forums.nasioc.com/forums/atta...3&d=1368574559
the pin is attached to each wire as seen in the pic, one pin per wire. Sometimes the pin is naked with no wire attached. You remove the pin from the junkyard block.

You solder your car's wire direct to the pin or solder to the wire already on the pin. Then push the pin into the correct space on the terminal block on your car, it clicks when seated.
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Old 07-17-2013, 12:26 PM   #18
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Quote:
Originally Posted by mhoerath View Post
the pin is attached to each wire as seen in the pic, one pin per wire. Sometimes the pin is naked with no wire attached. You remove the pin from the junkyard block.

You solder your car's wire direct to the pin or solder to the wire already on the pin. Then push the pin into the correct space on the terminal block on your car, it clicks when seated.
Got ya. So, in my case, I'd probably just want to get the plug with a pigtail amount of wire coming out anyways. Then I'd have my choice of color and have some extra if I mess up.
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Old 07-17-2013, 01:14 PM   #19
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Quote:
Originally Posted by ilarson007 View Post
Got ya. So, in my case, I'd probably just want to get the plug with a pigtail amount of wire coming out anyways. Then I'd have my choice of color and have some extra if I mess up.
yup. a junkyard will sell you the block with cut wires or if you do the work yourself you'll cut the wires as shown. check hondas, older subarus had different terminal blocks.
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Old 07-17-2013, 01:25 PM   #20
ilarson007
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The block from an 07 should be the same as my 02, right? If not, that will be really fun cutting and soldering wires...
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Old 07-17-2013, 03:45 PM   #21
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check the color - aqua - and if same color than prob the same pin type.
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Old 07-17-2013, 08:08 PM   #22
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Quote:
Originally Posted by 02CWRX View Post
No easy way to change the actual display from C to F that I am aware of, but a rough estimate to convert is to multiply by 2 and add 32. That at least gets you within a few degrees, haha. Side note, I would LOVE LOVE that MPH cluster. It's a UKDM cluster I'm guessing, I wish I could have found one of those when I was doing my swap.

Glad the write up could help a couple people.

~T.J.
Yep it's a UKDM cluster. I searched ebay.co.uk and found it for $115 shipped. It's never too late to get one.
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Old 07-17-2013, 11:27 PM   #23
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Quote:
Originally Posted by zach_rice View Post
Yep it's a UKDM cluster. I searched ebay.co.uk and found it for $115 shipped. It's never too late to get one.
Again, it's a simple programming change in the chip that stores the mileage.
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Old 07-18-2013, 09:57 AM   #24
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I've got one v8 Sti prodrive clusters for sale with DCCD blue faced
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Old 07-31-2013, 12:43 PM   #25
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So my plan is to put the sensor in the intake track, post intercooler. Anyone have any ideas on how to seal it to hold boost?
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