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Temperature Sending Unit

Posted: 23 Jul 2020 12:00
by Beev
Hi,

I am positive that I have a 3/8 NPT fitting for my temperature sending unit. I am not sure what the housing is out of, I suspect it has been modified. I currently use it for fan control but recently moved that over to my microsquirt. I want the dash gauge to work again. Anyone know if the threaded RA auto will work (WVE 1T1181) or is it BSP? Anyone have an alternative suggestion?



Thanks,

Bevan

Re: Temperature Sending Unit

Posted: 24 Jul 2020 23:48
by Byron510
I have ordered adaptors from Lordco to go from JNP to NPT threads.
Similar adaptors are available for the oil pressure sensor hole - or 1/8”, one is 27 tpi, the other is 28 tpi. A bit of a PITA, really.

I don’t recall what the original fitting thread size and pitch is, but I bet I can dig up an original thermostat housing for you that has not been modified- and likely still as an original 50 year old sensor in place :-)


Byron

Re: Temperature Sending Unit

Posted: 25 Jul 2020 07:41
by datzenmike
Fan control should be on the bottom of the rad or in line on the bottom rad hose. On the thermostat housing you are reading the hottest water and ignoring what the rad does. The fan will be on even when it doesn't have to be.

I don't see an opening for the by-pass hose so probably a 510/521 housing. Be sure your thermostat has a 'jiggle valve' or drill a 1/8 hole in it to promote circulation past the thermostat in lieu of a by-pass. The fitting on the side is for a TVV on an L20B but strange it has this but no by-pass.

Re: Temperature Sending Unit

Posted: 26 Jul 2020 08:45
by Byron510
I have only seen water temp/fan sensors located at the hottest part of the engine - which is generally the thermostat housing, or in many cases where European engines are concerned, the fan sensor is on the radiator - like VW rads.

https://www.hotrod.com/articles/tech-qa ... -location/
However there seems to be many opinions...
https://grassrootsmotorsports.com/forum ... 133/page1/

I’ve generally used the thermostat housing, the rad tank outlet - and both worked just as well to be honest. It’s all backed up by mechanical gauges and engine temp has been consistent.
What didn’t work was my very first electric fan set up, the Hayden fan was fine (but noisy - however things have improved since the 90’s), but I used a controller that had the probe insert into the fins of the rad. It was very inconsistent, and would come on my sooner when parked than in motion - almost 15 degrees difference which I felt was unacceptable.

Mike is right, you need to have some coolant flow is not using the bypass hose around the front of the engine. I have found that even the bypass hole in the thermostat (if there) was not large enough, and I had to drill it out to 3-4mm - 1/8 or 3/16”. Otherwise the water in the head would get to over 220 before the thermostat opens, and you could watch the gauge slap up to 220 plus when the thermostat finally opens, then drop back to 170 all in about 3 seconds - you imagine what that does to shock the motor? Anyways - bypass hole or bypass hose - it’s needed :-)

Byron

Re: Temperature Sending Unit

Posted: 26 Jul 2020 23:04
by Beev
Ha I think this is getting a little side tracked. I have full control of when my electric fans. I can set when they turn on or off so it doesn't really matter where I measure it from. I want to remove my old thermostat switch and replace it with something I can hook up to the stock gauge in the dash. I know the switch is a 3/8 NPT thread. What are my options stock (none because they are BSP?) and how about after market? I am guessing someone drilled out the BSP to 3/8 but interesting it would be a 510/521. I currently only have the standard bypass hole in the thermostat but don't have an issues with that.

Re: Temperature Sending Unit

Posted: 27 Jul 2020 06:53
by Byron510
If stock is what your after regarding the sending unit, I believe the stock temp probes are still available through the aftermarket, not sure about Nissan’s supply. But you will have to buy a new Nissan nut which will bolt it in place - these are available through Nissan.

If the hole had been tapped out to 3/8 NPT, And your looking for a temp probe that will work with the stock gauge, I’ve personally not gone down that route. Maybe someone here has and can chime in.

Byron

Re: Temperature Sending Unit

Posted: 08 Sep 2020 15:36
by yenpit
FYI the OEM collar that holds the OEM sensor in place is still available from Nissan......I use Riley at Lynchburg. Sorry, I'm not at my shop, so can't measure.......

The OEM temp sensors are also available from Nissan. I've had trouble with aftermarket sensors, so I only use OEM!