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Yet another question about aftermarket water temp sender

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Old 02-09-10, 04:32 PM
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Yet another question about aftermarket water temp sender

So I have searched..... and read a million threads about it.... but all the pictures and comments seem to be more 3rd gen specific.
I have an idea I am tossing around - and I want everyones opinion...
I found this pic on this site from someone that tapped the TB coolant line on his 3rd gen.


I was thinking about doing the same, with a different line.

There is a hose in the 2nd gen FC that goes from the engine block to the heater core in the firewall. This should work just as well right?

Please give me your feedback. I am going to try this in the morning if everyone agrees.
Old 02-09-10, 05:18 PM
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I wouldn't tap that spot because I'm pretty sure that coolant only flows through that line when the heater is switched on and calling for heat. You're in FL so I'm doubting you use the heat very much, certainly not in the summertime. I would think that putting the sensor in that spot, out of normal coolant flow, would bring you a 'dead' reading - it would be like tapping the sensor into the CAS and saying, 'Well, I'll know the engine temperature because as the engine warms up, so will the CAS.'

I would go with a 'live' spot where the coolant is flowing all or at least most of the time. The water pump housing is probably the most-popular spot. It's what I chose.

https://www.rx7club.com/showpost.php...2&postcount=21
Old 02-09-10, 05:28 PM
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Originally Posted by Amur_
I wouldn't tap that spot because I'm pretty sure that coolant only flows through that line when the heater is switched on and calling for heat. You're in FL so I'm doubting you use the heat very much, certainly not in the summertime. I would think that putting the sensor in that spot, out of normal coolant flow, would bring you a 'dead' reading - it would be like tapping the sensor into the CAS and saying, 'Well, I'll know the engine temperature because as the engine warms up, so will the CAS.'

I would go with a 'live' spot where the coolant is flowing all or at least most of the time. The water pump housing is probably the most-popular spot. It's what I chose.

https://www.rx7club.com/showpost.php...2&postcount=21
I know that water is constantly flowing through this hose. I recently sprung a leak in it and I have never turned my heater on... I actually have removed the controls for the custom dash I have.
BUT.... I really like your idea... I am actually going to do it exactly the way you have in your pics.
Thanks!
Old 02-09-10, 07:44 PM
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Water temp install, T-install

That's exactly what I did. Only tapped into the hose running from the BAC to the block. See picture:
Attached Thumbnails Yet another question about aftermarket water temp sender-001.jpg   Yet another question about aftermarket water temp sender-002.jpg   Yet another question about aftermarket water temp sender-003.jpg  
Old 02-09-10, 08:39 PM
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Originally Posted by K-Tune
FC3S does not use a heater valve, so coolant will always be flowing through the heater core.

it uses a flapper door to divert the air flow through the evaporator instead of the heater core, or vise versa.
This is complete and total bullshit. Don't post if you don't know what you're talking about.

The water valve is part number FB01-61-A40, controlled by the temp actuator, part number FB01-61-A60A.

Found on the drivers side of the car, just above the transmission tunnel.

No coolant flows through the heater core when the temp indicator is set to cold.
Old 02-09-10, 08:43 PM
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Originally Posted by K-Tune
FC3S does not use a heater valve, so coolant will always be flowing through the heater core.

it uses a flapper door to divert the air flow through the evaporator instead of the heater core, or vise versa.
yep, it sure does have a heater flow control valve. pull of the plastic cover at the driver's side of the heater core cover and you can see it right next to the core.
Old 02-09-10, 09:01 PM
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Makes no difference where I am from. I could ask if all Americans are this ignorant, but I know its not the case.

I don't put up with people posting misinformation just for the sake of increasing their post count. It is extremely irritating to watch someone tell someone how to do something completley false. I would hope you would rip on me if I went and told someone to wire their house with 20 gauge speaker wire.
Old 02-09-10, 09:59 PM
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You can also tap the back of the water pump housing, so that the sensor's not right next to the belts and pullies. There's a nice boss there that you can drill out and tap next to the stock sensor. It's not that hard to do and I for one never regret doing things the right way.
Old 02-09-10, 10:03 PM
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Originally Posted by XRobber
I know that water is constantly flowing through this hose. I recently sprung a leak in it and I have never turned my heater on
There's a difference between Pressure and Flow. That hose is under pressure. There's nothing isolating that hose from the coolant in the rest of the system. But there is a gate within the heater core that, when closed, prevents the coolant in that hose from moving. The hose will certainly see heat from the engine, but it won't be a 'live' reading.

If you had a house and you were deciding where to put the thermostat, would you put it in a fairly central location or would you put it at the end of a long hallway that had no vents nor other sources of air circulation? Which location would have the more useful, more realistic reading?
Old 02-09-10, 10:06 PM
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Originally Posted by Black91n/a
You can also tap the back of the water pump housing, so that the sensor's not right next to the belts and pullies. There's a nice boss there that you can drill out and tap next to the stock sensor. It's not that hard to do and I for one never regret doing things the right way.
I vote this ^^^
Old 02-10-10, 10:58 AM
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Copied and pasted from the FAQ:

Where do I install the sensor for my aftermarket temperature gauge?
There has been lots of discussion about where to mount water temp sensors/senders. The best location is on the water pump housing near the stock ECT (Engine Coolant Temperature) sensor. Drill and tap according to the threads on your sensor (usually 1/8" NPT). It is important this this sensor be installed before the thermostat. See the following topics for more information:
https://www.rx7club.com/forum/showthread.php?t=512268
https://www.rx7club.com/forum/showth...ender+location
https://www.rx7club.com/forum/showthread.php?t=361867
https://www.rx7club.com/forum/showthread.php?t=14683
https://www.rx7club.com/forum/showthread.php?t=430129
https://www.rx7club.com/forum/showthread.php?t=403701
https://www.rx7club.com/forum/showthread.php?t=137824
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