# Temp Gauge wiring



## dreamteam (Jul 29, 2005)

I am installing an aftermarket temp gauge. 1992 sentra E
Did a search and found the coolant gauge sensor is located behind/below the distributor. Is this correct, and will an aftermarket gauge function on this sensor?


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## smj999smj (Jan 1, 2006)

I believe it is under the distributor. Should be a single wire, yellow with a green stripe. If it's not there, check near intake manifold runner #1 near the ECT sensor. Aftermarket gauge may work with the factory coolant sensor, but you should check with the gauge manufacturer to be certain.


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## LvR. (May 26, 2010)

that................ and also remember that even if the new gauge spec says its fine ito sensor properties, then you cannot operate both the original and new gauge off the same sensor - they each need individual dedicated sensors


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## M.J. (Aug 29, 2002)

*I agree with LVR and the calabration of the guage may be*

Still slightly off a bit. but after time of monitoring it for a while you would be able to establish a normal temp or range with it.
Just trying to help the cause.


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## LvR. (May 26, 2010)

M.J. said:


> Still slightly off a bit. but after time of monitoring it for a while you would be able to establish a normal temp or range with it.
> Just trying to help the cause.


You are screwing the pooch if you run like that .................... that is if you are even lucky enough to get any deflection at all. The whole idea is to have an accurate temp gauge so you can see the actual temp - if you get used to an indicator sitting right at the edge of its scale saying you are boiling hot or ice cold all the time even though you are not, you can just as well go put your finger on the exhaust and figure the engine temp from that too


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## M.J. (Aug 29, 2002)

*After giving it some thought,*

I should know better. It would be pointless to put a temp gauge or any other gauge in a vehicle for that matter if, it was'nt going to be accurate.

Sorry, error in my own judgement on that one.


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## dreamteam (Jul 29, 2005)

*Update*

OK,so the aftermarket temp gauge is in and working.
We first tried wiring it to the factory sensor, no reading.
Then we installed the sensor that came with the gauge, good reading.
Didn't want to put the new sensor in the block, so we installed it in the top of the radiator. Pics soon.


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## LvR. (May 26, 2010)

dreamteam said:


> OK,so the aftermarket temp gauge is in and working.
> We first tried wiring it to the factory sensor, no reading.
> Then we installed the sensor that came with the gauge, good reading.
> Didn't want to put the new sensor in the block, so we installed it in the top of the radiator. Pics soon.


OK then - humor us .................... why are you installing a temp gauge?

IMO its currently completely useless ito telling you whats happening with the engine temp and only slightly more useful than no temp gauge at all


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## dreamteam (Jul 29, 2005)

LvR. said:


> OK then - humor us .................... why are you installing a temp gauge?
> 
> IMO its currently completely useless ito telling you whats happening with the engine temp and only slightly more useful than no temp gauge at all


 I removed the cluster and attempted to swap in a tach from a 93 SE-R cluster.
Only to find out that the tach was electronic and not analogue. So, I then re-swapped everything back to original and in the process knocked the needle off the factory temp gauge.
Now I had no good way to calibrate the factory temp gauge. I replaced the needle on what I thought was the correct setting. I was way off. The needle would rise all the way to the top in just minutes. Ergo the need for a secondary gauge to tell me the correct water temp.


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## jdg (Aug 27, 2009)

Fire it up, wait for awhile, at least until you think the temp has stabilized, put the needle in the middle of the range.
That's how 'most' temp gauges are set up anyways...at least on everything I drive...give or take a bit. The normal temp never sits down at the bottom, never sits up at the top, always in the middle. If it ain't in the middle, something's up. Besides that, most, if not all, temp gauges, senders, etc. are non-linear, unless they're electronically driven (i.e. stepper motors driven directly by the ECU).


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## Houlamiller (Mar 22, 2012)

Oh thank for discussion i also have same problem, wondering to use these techniques


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## LvR. (May 26, 2010)

> Didn't want to put the new sensor in the block, so we installed it in the top of the radiator. Pics soon


Well ................. That is the crux of the issue.

This means the temp sender is not seeing the block temp at all and the new gauge will be under-reading by probably at least a few degrees even in the best ideal conditions. The correct installation method in this case is to replace the OEM temp sender unit in the block with the aftermarket sender unit .............................

If you don't do it this way the engine can eg overheat due to a stuck thermostat and the newly installed meter will still show it to be ice cold...................... and many many various other disaster conditions costing a lot of money will also not be detected/indicated with your current installation practice


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## dreamteam (Jul 29, 2005)

*Gentlemen: start your engines!*

I enjoy your banter and input.
Yes, fellow ND'er I intend on replanting the needle at operating temp.
However, there is good and bad in everything. currently I am able to watch these two gauges perform a service in tandem. As the needle is now set to the cold side, I am able to watch the block temp rise more precisely. And, just as it reaches the top, the thermostat opens and the water gauge is able to track the radiator temp.
Having the sensor in the radiator also provides a few other advantages.
I now know when the fans are working as the temp drops approximately ten degrees. If the coolant level drops the gauge will also indicate that, and, up here in the north it can get quite cold in the winter. The radiator temp will indicate when the thermostat is opening and for how long.


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## LvR. (May 26, 2010)

dreamteam said:


> As the needle is now set to the cold side, I am able to watch the block temp rise more precisely. .................


Erm - "precisely"? - care to elaborate on this?

IMO you cannot achieve this because the gauge's sensitivity is exactly what it was before you moved the needle - it now just sweeps/points to a different section of the scale


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## dreamteam (Jul 29, 2005)

LvR. said:


> Erm - "precisely"? - care to elaborate on this?
> 
> IMO you cannot achieve this because the gauge's sensitivity is exactly what it was before you moved the needle - it now just sweeps/points to a different section of the scale


Hhmmm,sensitivity may not be the correct word, here.
I have surmised that when I moved the needle, it caused the needle to travel much further up the gauge to show the same temp.
For example: the half way point on the gauge before I moved the needle was about 190 degrees. Now the needle needs to travel all the way to the top to indicate that same 190 degrees. Therefore the half way point is now about 130 degrees. This should make the gauge more sensitive to cooler temps. I am going to guess that the needle now starts to climb at about 90 degrees.
If I have surmised this correctly, that means a factory calibrated gauge does not start to climb until about 130 degrees.


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## LvR. (May 26, 2010)

Nope - that argument addresses *sensitivity and range*. Thats why I said your moving the needle means no effective change in detectable temperatures .................. the gauge was designed and constructed many moons ago - no matter what you do to the needle alone, you cannot effect a change in behavior - the electronics/mechanicals determines the range of temperature of operation - it may indeed start moving only at 130 or whatever, but you cannot change that characteristic with a simple needle displacement. Irrespective of the needle position you decide to mount it in, the meter itself knows nothing about its ability to *accurately* "display" the temperature to you - its electronics/mechanicals were designed to indicate a certain range while sweeping the whole face of the guage and that design is fixed irrespective of your needle position placement.


If you are saying something else, then let me ask you this - with the engine ice cold, where is the needle pointing to? ..........................iow are you in effect saying you are making use of the "dead-band" to effect a wider "display sweep range" ....................... if so I do follow your argument, but then you are screwing the pooch again on the "hot" side where the meter's movement will not be able indicate high temps properly again (the meter movement will get stuck at some high temp rather than continue to climb with increasing temps).

As I said - its a question of sensitivity and range of interest. I guess if you are "interested" more about seeing when the coolant starts warming up, then fine.


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## jdg (Aug 27, 2009)

Might be two different ball games here, but.....
If the temp gauge on the B13 and B14 are wired the same (i.e. same parts, and so on), on both of my B14's, the temp gauge STARTs to move off the low peg at 135F (about what the O/P got), and is centered at about 180F.

Normal thinking would dictate that if you got 45F of travel at the bottom end of the scale, you'd get another 45F at the top end of the scale, i.e. 135F bottom, 180F middle, 225F top.
But, since the thermistor resistance is a non-linear relationship (temp vs resistance), that isn't the case.
However, due to the fact that the relationship is non-linear, it does actually smooth out quite a bit above 120F (give or take), so 135F/180F/225F bottom/middle/top would seem to be pretty much right on.

But as LvR said, the design of the meter, needle sweep, electronics, etc. aren't going to change just because you changed the needle position.
It's still going to begin doing something at 135F and stop doing something at 225F, regardless of needle placement.

After market temperature indicators might not have those limitations, but I'm thinking the stock gauges read from X to Y and that's it.

Could do what I did...make extra little ticks on the face of the gauge while taking readings with an OBD scanner. For the hot side of the scale, I pulled the temp sensor out, put it in boiling water, read the resistance across the sensor, put an equivalent resistance (I want to say 130ohms??? but I'm probably wrong, long time ago) in the car, made a tick mark right at 209F (at my altitude, average baro pressure). Doesn't do any good for any hotter than that, but I can't boil water any hotter than that....at least not very easily.


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## dreamteam (Jul 29, 2005)

*here's the pic*

Good arguments guys!
The reason I have for stating my discussion is that when I replaced the needle on the gauge, There seemed to be more room for movement at the bottom of the gauge than at the top of the gauge.
In other words, I think that on the factory setting the needle stops short on the cold side.
That said, here's the picture.
I drilled a hole the correct size in the plastic top of the radiator.
Then I tapped it for the correct thread size.
I used RTV to seal it.
The hose clamp is for the ground wire.(needed here because of the plastic)


















You will want to drain the radiator about half way
before you start. Use a shop vac to suck out the coolant that remains near the opening'
I also used a hair dryer to help set up the RTV.
As usual, it's best to swab the area with alcohol and a Q-tip(make sure it's dry) before applying sealant.


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## dreamteam (Jul 29, 2005)

*gauge temp pic*

So here's the gauges at normal temp.


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