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2012 Outback 3.6R Premium
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Discussion Starter #1
Hi All:

I've been wanting to install an aftermarket temp gauge for my 2012 3.6R, and was wondering which radiator hose to tap into for the sensor? I know there are options for the gauges that fit into the OBDII port, but I really don't like the looks of them and would prefer more of a regular "gauge" with a needle and such over a digital readout.

Searched around on several Legacy forums but with no luck on which hose.

Any help is greatly appreciate it! Thanks!
 

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2011 OB 2.5i Prem CVT HK/AWP, Ruby Red Pearl
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3,321 Posts
Well, it can't be on a ‘hose’… that’s going to leak (if not blow out). It needs to be on a threaded manifold/block/housing (somewhere).<O:p</O:p
The OBD2 port actually seems to be the simplest/cleanest approach, with a digital dial/needle display/interface.<O:p</O:p
 

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2012 Outback 2.5i CVT
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The upper radiator hose is the return one, which is where you would want to take the reading. So what type of sensor would you get that mounts on the hose? I haven't seen one like that.
 

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^^What GasGuzz said^^

The sensor would have to be in the flow of coolant to get an accurate reading. Now, there are adapters to put a sensor in the upper radiator hose, but those are only accurate when the thermostat is open and the coolant flowing.

http://www.ebay.com/itm/38mm-Water-...pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

Quicker and easier is something like:

Scangauge II Scanguage 2 OBD2 Auto Computer Code Reader | eBay

or:

http://www.ebay.com/itm/TurboGauge-IV-OBD2-4-1-Car-Auto-Trip-Computer-Digital-Gauge-Scan-Tool-Scanner-/150921188618?hash=item23239a950a&item=150921188618&pt=Motors_Automotive_Tools&vxp=mtr
 

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Discussion Starter #6
Bradze:

I waas thinking of either on the steering column, or take out the defrosting vent and mold a cup mount into it.

GasGuzz, vtmecheng:

The gauge manufacturer sells a hose adapter that's made from aluminum with a hole for the sensor to screw into. Here's a link on it (it's towards the bottom):

Sensor specification | Defi – Exciting products by NS Japan

I personally like this gauge, but there are others out there:

ADVANCE CR Water temperature | Defi – Exciting products by NS Japan

So about the upper radiator hose, is that where you would want to tap into? Which way does the coolant flow? I'm trying to figure out which hose to tap into to get the closest temp, the one flowing out or flowing into the radiator?

I know this is not as accurate as a sensor tapped into the block, but I just really don't like the look of the other options like Scangauge, etc. Also, isn't the most important thing about temp gauge the upper ranges? Which by then, the thermostat should have openned and the coolant should be flowing between the radiator and engine right?
 

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You do not want to put the sensor on any hose to or from the radiator. Every time the thermostat opens or closes, your temp guage will go nuts.
 

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2013 3.6R SAP BBP Outback
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Before you cut into your cooling system, firewall, dashboard, and make a mess, run a Google search for analog gauges that plug into the OBDII port. There are many, including several with customizable analog (or digital) displays for parameters of your choosing. All of the multi-display mode gauges can display temp (engine, transmission, or exhaust gas, etc.). This would be much more accurate, reliable, and easier way to get the temp displayed in analog, with the added bonus of having a code reader/clearer always at hand (all the multi-use devices I found that plug into the OBDII port can read/clear codes too).
 

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2015 2.5i Limited Carbide Gray
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I would look into the wiring for the idiot light for the dash and see if you can't tap into that with an aftermarket gauge. Just because Subaru was too short sighted to put a gauge in the cluster doesn't mean they aren't interested in the temperature of the coolant. I would think that there has to be some sort of sensor somewhere. The ECU has to have some reference from somewhere.
 

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I would strongly recommend going with a OBDII plug-in system for both simplicity and accuracy. Putting a sensor on the cooling line will have reduced accuracy because coolant only flows once the car is warm enough for the thermostat to open. Also, you are introducing another connection to the cooling lines which just means another point of possible failure. Isn't it just easier and cleaner to plug into the OBDII port and call it a day?
 

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I would look into the wiring for the idiot light for the dash and see if you can't tap into that with an aftermarket gauge. Just because Subaru was too short sighted to put a gauge in the cluster doesn't mean they aren't interested in the temperature of the coolant. I would think that there has to be some sort of sensor somewhere. The ECU has to have some reference from somewhere.
There is a sensor on the engine, actually there are a couple, which take temperature readings for the ECU. What would be difficult is finding an aftermarket gauge that can take the simple voltage drop signal provided by the sensor and translate that to the proper temperature across the range of readings it will output. The gauge needs to know that say 0.8 V is 102 degF and 1.2 V is 183 degF. From an graphical point of view the gauge would need to know the Y intercept point and slope for the line which represents temperature vs. voltage.
 

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Discussion Starter #12
I agree with everyone's suggestion on a gauge that plugs into the OBDII port, and also agree it is the simplest and most accurate method. However, I don't think any of the current crop of offerings look anything like the gauge I listed in my link. In case there's any confusion, I want something that actually has a needle that moves around, like the stock gauges, and not something that is displayed on a digital screen to represent a needle.

I also agree with the fact that whenever you introduce an additional joint into the system, it is an additional point of possible failure, but they seem very well made, thus should be pretty durable. Granted, it may not be as durable as the original uncut hose, but it's not too much of a compromise is it?

An additional food for thought: if these gauges and their methods of installation are inaccurate and causes reliability issues, then why is it that these gauges are very common in most high performance cars? You would think these cars are under much higher degrees of stress than our Outbacks will ever be exposed to right? Pick up a copy of "Modified" and you will see that most of the cars inside have additional gauges installed to monitor critical stats of the engine, and I can tell you, not all are hooked up directly to the ECU (or any other form of aftermarket engine management system) or utilize sensors that are tapped into the engine block for temp measurement. So the people who tune those cars, do they not know what they are doing?
 

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I say go for it, and let us know how it works out.

I agree with everyone's suggestion on a gauge that plugs into the OBDII port, and also agree it is the simplest and most accurate method. However, I don't think any of the current crop of offerings look anything like the gauge I listed in my link. In case there's any confusion, I want something that actually has a needle that moves around, like the stock gauges, and not something that is displayed on a digital screen to represent a needle.

I also agree with the fact that whenever you introduce an additional joint into the system, it is an additional point of possible failure, but they seem very well made, thus should be pretty durable. Granted, it may not be as durable as the original uncut hose, but it's not too much of a compromise is it?

An additional food for thought: if these gauges and their methods of installation are inaccurate and causes reliability issues, then why is it that these gauges are very common in most high performance cars? You would think these cars are under much higher degrees of stress than our Outbacks will ever be exposed to right? Pick up a copy of "Modified" and you will see that most of the cars inside have additional gauges installed to monitor critical stats of the engine, and I can tell you, not all are hooked up directly to the ECU (or any other form of aftermarket engine management system) or utilize sensors that are tapped into the engine block for temp measurement. So the people who tune those cars, do they not know what they are doing?
 

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2015 2.5i Limited Carbide Gray
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There is a sensor on the engine, actually there are a couple, which take temperature readings for the ECU. What would be difficult is finding an aftermarket gauge that can take the simple voltage drop signal provided by the sensor and translate that to the proper temperature across the range of readings it will output. The gauge needs to know that say 0.8 V is 102 degF and 1.2 V is 183 degF. From an graphical point of view the gauge would need to know the Y intercept point and slope for the line which represents temperature vs. voltage.
I understand the relationship would still have to exist, but I wonder if the aftermarket senders don't work in the same way. Another option could be the simple thermocouple like dakota digital uses for some of there temperature gauges.

I wonder if a '13 cluster has the same harness plugs as the '10-'12. I know the new cluster has a different center section but I wonder if the new cluster would plug in.
 

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...one word...Ultraguage.

Gives me my engine temp along with a host of other guages that nice to have.
 

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Discussion Starter #16
Thank you for your suggestion, but again, an actual analog gauge with a needle that moves is my goal. Again, I agree the digital gauges using OBDII are easy and accurate, but not what I'm looking for.
 

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I understand the relationship would still have to exist, but I wonder if the aftermarket senders don't work in the same way. Another option could be the simple thermocouple like dakota digital uses for some of there temperature gauges.

I wonder if a '13 cluster has the same harness plugs as the '10-'12. I know the new cluster has a different center section but I wonder if the new cluster would plug in.
I thought only SAP models had a different gauge cluster (including an analog temp gauge) for 2013 and all non-SAP models had the same cluster as 10-12.
 
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