How to modify the stock dummy water temp gauge to real water temp gauge?

SuperTurbo · 01-29-2008, 12:29 AM

OK... at the NA gauge post, we all understand that the temp gauge inside the dashboard is a dummy gauge.

So... can we modify the wiring or cut some parts off to make it become a real gauge?

If we can do that, in another word, we can put 1 more gauge into that slot.

impreza_GC8 · 01-29-2008, 02:04 AM

I'm not sure I understand what you are saying....I would like to know though. I was under the impression my temp gauge was "real" LOL.

EDIT:
Is this what you are referring to? (Stolen from another thread

Quote:

Originally Posted by H-Dtech

the stock subie water temp gauge is basically a dummy gauge, its only moves at set temps. so when your car is first warming up it won't move until a set temp, then when it is at normal operation temp. it won't move until temps get into a dangerous area. basically they didn't want every commuter idiot that didn't know anything about cars bringing in there car every time they got stuck in traffic and the temps climbed abit. so the stock gauge only gives you enough info to get into trouble, and not enough to prevent it.

SuperTurbo · 01-29-2008, 12:08 PM

Bingo! that's what am I referring to!

I just don't want to buy put so much of those stuff into the car, and attract Police & Thief's attention!

2.5i · 01-29-2008, 01:16 PM

I didnt know gauges attracted the attention of the police.

joecerv · 01-29-2008, 03:06 PM

In older cars, I can remember cars from the late 70's, that the temp gauge provided an actual reading.

As indicated above:
"basically they didn't want every commuter idiot that didn't know anything about cars bringing in there car every time they got stuck in traffic and the temps climbed abit."
that the manufactures made the 'upgraded' temp gauge.

Take a look at the MY08 impreza 2.5i. The temp gauge has been replaced by a dummy light that stays on until it reaches safe normal operating temperature.

I do not have an answer, but, I do believe it can be done.

RaceFaceXC · 01-29-2008, 08:14 PM

Does anyone know what type pf sending unit is used? If you know the sending unit (I think voltage range is really the only important detail) then you should be able to wire the OEM sending unit to any gauge that is compatible. If the sending unit is a "dummy" sending unit (only sends a cold/hot signal) then the gauge you use wont help. Need more info! And out of curiosity, being a dummy unit, how does the OEM gauge climb from cold to operating temp slowly? Seems like a dummy unit would be either all the way cold or almost immediately at operating temp once the sending unit gave it the signal. Feed my brain!

Plays_With_toys · 01-29-2008, 11:59 PM

That's wierd... See my temp gauge gradually rises with the warming of the motor. And further more, earlier, the gauge deflected 3-4 degrees of angle while sitting at a light (I'm having cooling issues). It's also gone up 3/4 of the way, and as soon as I got moving in traffic again it began dropping down. Now you're saying these things aren't really actively giving the driver info?

Patrick Olsen · 01-30-2008, 04:29 AM

No, they're not. My factory gauge sits at its "normal" indication with actual coolant temp being anywhere from 70 - 100*C. I haven't had temp any higher than that, so I don't know at what point the gauge will budge. 70*C is well below the thermostat setting, so 70 is not what I would consider "normal", but the gauge thinks it is.

This isn't just a Subaru thing. There are very, very few cars that have real gauges, and it's for exactly the reason that H-Dtech said (and that I've said in other threads).

As for the original question, unless you're going to tear apart the instrument cluster and put a new gauge head behind the existing gauge face I don't see any way to make the dummy gauge into a real gauge.

Pat Olsen

subikid · 01-30-2008, 10:23 AM

Pat and OP,

Excuse any typos, I'm on my phone...

My aftermarket temp gauge follows the oem gauge almost perfectly (or visa versa). Also, when I driver slowly or let it warm up just sitting, the oem temp gauge goes slowly up, following my other temp gauge.

Another thing I notice is the popping we get sometimes. When my car is very cold and you get on it (don't do that!) and shift, it doesn't pop. However, as the oem temp gauge goes up a little, in between the first and second hash, and you get on it, when you shift, I get an EXTREMELY loud pop, so loud it has scared people. Then, when the oem temp gauge reaches normal operating temp, no more extremely loud popping.

I say this because I based my driving on my oem temp gauge before I got my aftermarket, so that I didn't pop and scare people sheeetless.

Based on these things, I don't think the oem gauge (at least for the 05) is a dummy, but I do think that it works in intervals, maybe of 5 or10 degrees, and thus slowly rises, paralleling my other wt gauge.

Kevin

RaceFaceXC · 01-30-2008, 07:42 PM

well i think it depends on the sending unit more than the gauge.. the gauge would be more complex as a "dummy" gauge than if it were just a voltage sensitive gauge. and the sending unit could be a "dummy" quite easily with the use of a bimetallic strip or bellows, etc. I would guess the newer stuff is a solid state sending unit and im sure they could make it send whatever signal they want @ whatever temp they want with that type. Still, no one knows if the sending unit is the "dummy" or if its the gauge?

RyanE · 01-31-2008, 12:13 PM

My Legacy has a "dummy" gauge as well, so I poked around in the service manual to see what the schematics say. In my car, the gauge gets its info from the ECU. I think that would make it pretty hard to make it accurately move.

You folks might want to get ahold of the factory service manual page that shows the "combination meter" (instrument panel) wiring diagram and see if that's the case for your cars as well.

-Ryan

8Complex · 01-31-2008, 12:41 PM

I know the ECU gets a real temperature reading off of the stock sensor, so I suppose it'd just be a matter of making tick marks on the dash gauge at certain temperatures so you're actually able to read it.

RyanE · 01-31-2008, 01:50 PM

Quote:

Originally Posted by 8Complex

I know the ECU gets a real temperature reading off of the stock sensor, so I suppose it'd just be a matter of making tick marks on the dash gauge at certain temperatures so you're actually able to read it.

I think the OP's desire was to have a gauge that fluctuated as the motor heated and cooled, such as when the car was stopped in traffic. The (late model only?) stock gauges are "damped" or "dummy" gauges so that they don't move from the middle position unless it's almost too late.

-Ryan

RaceFaceXC · 01-31-2008, 09:32 PM

Does the ECU send the gauge real temp data that is "dampened" @ the gauge or does the ECU do the "damping" to the signal it sends the gauge before it leaves? I guess im just trying to find out of the gauge being replaced with a accurate gauge will allow for accurate current temp readings or if the ECU needs to be reprogrammed to send the more accurate data to the gauge in the first place. I guess im asking about an 07 2.5i specifically but info about any year would be appreciated by someone im sure.

Guerice · 02-01-2008, 06:38 PM

Ok let me get this straight....

When you want to wire up a water temp gauge, whitch wire do you take?
The one going to the gauge or the one from the sensor?

Can you tell me what are the voltage of both wires from the service manual?

I know it's alot of questions but I think i can figure how to do it with those answers.
I'll check in my service manual too see if i can figure it out in the meantime.

01-29-2008, 12:29 AM	#1
SuperTurbo Scooby Newbie Member#: 152318 Join Date: Jun 2007 Chapter/Region: E. Canada Location: Toronto Vehicle: 2002 mazda mpv	How to modify the stock dummy water temp gauge to real water temp gauge? OK... at the NA gauge post, we all understand that the temp gauge inside the dashboard is a dummy gauge. So... can we modify the wiring or cut some parts off to make it become a real gauge? If we can do that, in another word, we can put 1 more gauge into that slot. Last edited by SuperTurbo; 01-29-2008 at 12:05 PM.

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01-29-2008, 12:08 PM	#3
SuperTurbo Scooby Newbie Member#: 152318 Join Date: Jun 2007 Chapter/Region: E. Canada Location: Toronto Vehicle: 2002 mazda mpv	Bingo! that's what am I referring to! I just don't want to buy put so much of those stuff into the car, and attract Police & Thief's attention!

01-29-2008, 01:16 PM	#4
2.5i Scooby Specialist Member#: 112986 Join Date: Apr 2006 Chapter/Region: NWIC Location: Camano Island Vehicle: N/A Cam'd & Cornfed DOM TUNED 06 Impreza	I didnt know gauges attracted the attention of the police.

01-29-2008, 03:06 PM	#5
joecerv Scooby Specialist Member#: 110459 Join Date: Mar 2006 Location: Somewhere in the DFW area Vehicle: 2006 Impreza 2.5i Steel gray metallic	In older cars, I can remember cars from the late 70's, that the temp gauge provided an actual reading. As indicated above: "basically they didn't want every commuter idiot that didn't know anything about cars bringing in there car every time they got stuck in traffic and the temps climbed abit." that the manufactures made the 'upgraded' temp gauge. Take a look at the MY08 impreza 2.5i. The temp gauge has been replaced by a dummy light that stays on until it reaches safe normal operating temperature. I do not have an answer, but, I do believe it can be done.

01-29-2008, 08:14 PM	#6
RaceFaceXC Scooby Specialist Member#: 165749 Join Date: Dec 2007 Chapter/Region: South East Location: stupid Florida Vehicle: 2007 No YELLING on the bus!	Does anyone know what type pf sending unit is used? If you know the sending unit (I think voltage range is really the only important detail) then you should be able to wire the OEM sending unit to any gauge that is compatible. If the sending unit is a "dummy" sending unit (only sends a cold/hot signal) then the gauge you use wont help. Need more info! And out of curiosity, being a dummy unit, how does the OEM gauge climb from cold to operating temp slowly? Seems like a dummy unit would be either all the way cold or almost immediately at operating temp once the sending unit gave it the signal. Feed my brain!

01-29-2008, 11:59 PM	#7
Plays_With_toys Scooby Specialist Member#: 82556 Join Date: Mar 2005 Location: Parker, Colorado Vehicle: 1996 Legacy L wagon	That's wierd... See my temp gauge gradually rises with the warming of the motor. And further more, earlier, the gauge deflected 3-4 degrees of angle while sitting at a light (I'm having cooling issues). It's also gone up 3/4 of the way, and as soon as I got moving in traffic again it began dropping down. Now you're saying these things aren't really actively giving the driver info?

01-30-2008, 04:29 AM	#8
Patrick Olsen NASIOC Supporter Member#: 120 Join Date: Jul 1999 Chapter/Region: AKIC Location: Where the Navy sends me... Vehicle: 1997 Legacy 2.5GT QuickSilver Metallic	No, they're not. My factory gauge sits at its "normal" indication with actual coolant temp being anywhere from 70 - 100C. I haven't had temp any higher than that, so I don't know at what point the gauge will budge. 70C is well below the thermostat setting, so 70 is not what I would consider "normal", but the gauge thinks it is. This isn't just a Subaru thing. There are very, very few cars that have real gauges, and it's for exactly the reason that H-Dtech said (and that I've said in other threads). As for the original question, unless you're going to tear apart the instrument cluster and put a new gauge head behind the existing gauge face I don't see any way to make the dummy gauge into a real gauge. Pat Olsen

01-30-2008, 10:23 AM	#9
subikid Scooby Specialist Member#: 114122 Join Date: May 2006 Chapter/Region: South East Location: St. Augustine, FL Vehicle: 1990 miata(RIP 05rs) red	Pat and OP, Excuse any typos, I'm on my phone... My aftermarket temp gauge follows the oem gauge almost perfectly (or visa versa). Also, when I driver slowly or let it warm up just sitting, the oem temp gauge goes slowly up, following my other temp gauge. Another thing I notice is the popping we get sometimes. When my car is very cold and you get on it (don't do that!) and shift, it doesn't pop. However, as the oem temp gauge goes up a little, in between the first and second hash, and you get on it, when you shift, I get an EXTREMELY loud pop, so loud it has scared people. Then, when the oem temp gauge reaches normal operating temp, no more extremely loud popping. I say this because I based my driving on my oem temp gauge before I got my aftermarket, so that I didn't pop and scare people sheeetless. Based on these things, I don't think the oem gauge (at least for the 05) is a dummy, but I do think that it works in intervals, maybe of 5 or10 degrees, and thus slowly rises, paralleling my other wt gauge. Kevin

01-30-2008, 07:42 PM	#10
RaceFaceXC Scooby Specialist Member#: 165749 Join Date: Dec 2007 Chapter/Region: South East Location: stupid Florida Vehicle: 2007 No YELLING on the bus!	well i think it depends on the sending unit more than the gauge.. the gauge would be more complex as a "dummy" gauge than if it were just a voltage sensitive gauge. and the sending unit could be a "dummy" quite easily with the use of a bimetallic strip or bellows, etc. I would guess the newer stuff is a solid state sending unit and im sure they could make it send whatever signal they want @ whatever temp they want with that type. Still, no one knows if the sending unit is the "dummy" or if its the gauge?

01-31-2008, 12:13 PM	#11
RyanE Scooby Newbie Member#: 118354 Join Date: Jun 2006 Chapter/Region: MWSOC Vehicle: 2005 Legacy GT LTD Regal Blue Pearl	My Legacy has a "dummy" gauge as well, so I poked around in the service manual to see what the schematics say. In my car, the gauge gets its info from the ECU. I think that would make it pretty hard to make it accurately move. You folks might want to get ahold of the factory service manual page that shows the "combination meter" (instrument panel) wiring diagram and see if that's the case for your cars as well. -Ryan

01-31-2008, 12:41 PM	#12
8Complex Moderator Member#: 922 Join Date: Feb 2000 Chapter/Region: MWSOC Location: Schaumburg, IL Vehicle: 04 FXT Red	I know the ECU gets a real temperature reading off of the stock sensor, so I suppose it'd just be a matter of making tick marks on the dash gauge at certain temperatures so you're actually able to read it.

01-31-2008, 09:32 PM	#14
RaceFaceXC Scooby Specialist Member#: 165749 Join Date: Dec 2007 Chapter/Region: South East Location: stupid Florida Vehicle: 2007 No YELLING on the bus!	Does the ECU send the gauge real temp data that is "dampened" @ the gauge or does the ECU do the "damping" to the signal it sends the gauge before it leaves? I guess im just trying to find out of the gauge being replaced with a accurate gauge will allow for accurate current temp readings or if the ECU needs to be reprogrammed to send the more accurate data to the gauge in the first place. I guess im asking about an 07 2.5i specifically but info about any year would be appreciated by someone im sure.

02-01-2008, 06:38 PM	#15
Guerice Scooby Newbie Member#: 51519 Join Date: Dec 2003 Chapter/Region: E. Canada Location: Moncton, NB Vehicle: 2000 SRP GF AKA Lilwgn	Ok let me get this straight.... When you want to wire up a water temp gauge, whitch wire do you take? The one going to the gauge or the one from the sensor? Can you tell me what are the voltage of both wires from the service manual? I know it's alot of questions but I think i can figure how to do it with those answers. I'll check in my service manual too see if i can figure it out in the meantime.