Water temp gauge

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JohnW
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Joined: Sun May 19, 2019 1:08 am

Water temp gauge

Post by JohnW » Sat Dec 28, 2019 4:30 pm

Who else is using a Smiths magnolia faced electrical type water temp gauge in a TC? If so what is the accuracy like?
I have one in mine and it reads a complete load of bo**ocks. My suspicions were first aroused when it climbed to approx 110deg c driving along the road. 110 deg in an un pressurised system? I don't think so !
The gauge and sender were removed and tested on the bench using a very accurate lab spec thermometer and the results showed it to be wildly (as much as 30 degrees out) inaccurate. I am not expecting it to be exactly correct, but within 5 degrees is not to much to ask for is it?
Anyone else using the same type of gauge ?
If not what is everyone using please?
Maybe I should add here that I have not had the car that long and have done limited milage in it so am still finding little issues with it.

Franz Tenbrock
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Location: Waltrop Germany

Re: Water temp gauge

Post by Franz Tenbrock » Sun Dec 29, 2019 2:31 am

Hello
i have a TA and a Spartan Kit car
in the spartan i use a simply tem gauge from the bay, printed a new dial so that it looks like the other instruments
you have to buy a temp gauge with its sender, and then order a dial from Declan Burns so that the colour and the design is right.
You get the gauge for 20 Euros, so really cheapFor the TA i think about to take a dual gauge, oil pressure and water temp as it is used in later cars. The TA has a Amp Gauge and a oil pressure gauge in the middle, no gauge on the side, so if i make a hole in the dashboard, it isn t right, and if i take the dual gauge also
Best Regards
Franz

English better every day ;-)
3D Print: CJR3 case for Lucas340, individual Titan-X spark plug holder for 30 Euros, original like case for replica speedo + tacho

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Steve Simmons
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Re: Water temp gauge

Post by Steve Simmons » Sun Dec 29, 2019 8:07 am

I would suspect the problem is the sender rather than the gauge itself. You should be able to order a new sender unit.
1949 TC8975 / XPAG 9609
1949 TC9849 EXU / XPAG 10507
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JohnW
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Re: Water temp gauge

Post by JohnW » Sun Dec 29, 2019 9:10 am

Steve Simmons wrote:
Sun Dec 29, 2019 8:07 am
I would suspect the problem is the sender rather than the gauge itself. You should be able to order a new sender unit.
I have tried quite a few senders and they are all giving approx the same results.

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Steve Simmons
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Re: Water temp gauge

Post by Steve Simmons » Sun Dec 29, 2019 9:38 am

In that case, I would contact the manufacturer and ask for specs on sender resistance. Then you can measure the sender(s) you have to see if they are working correctly. If so then the gauge itself must be faulty. A lot of vehicles like MGB, etc use Smith's electric water temp gauges and they seem to work well. The other option of course is to install an analog gauge, which is pretty much bombproof unless the capillary tube gets damaged.
1949 TC8975 / XPAG 9609
1949 TC9849 EXU / XPAG 10507
http://www.mgnuts.com

JohnW
Posts: 10
Joined: Sun May 19, 2019 1:08 am

Re: Water temp gauge

Post by JohnW » Wed Jan 01, 2020 1:57 pm

Steve Simmons wrote:
Sun Dec 29, 2019 9:38 am
In that case, I would contact the manufacturer and ask for specs on sender resistance. Then you can measure the sender(s) you have to see if they are working correctly. If so then the gauge itself must be faulty. A lot of vehicles like MGB, etc use Smith's electric water temp gauges and they seem to work well. The other option of course is to install an analog gauge, which is pretty much bombproof unless the capillary tube gets damaged.
Just out of interest I bought a new white faced water temp gauge and sender off ebay which came from China for the rip off :lol: sum of £6.40 inc postage :eek: I tested this on the bench to see how accurate it was ( or wasn't ), didn't expect it to be much cop as it was so cheap but was staggered to find it was within 4 degrees C all the way from 40 - 100.
Alas there is a downside to this as I discovered when I fitted it and couldn't get it to work at all ...............after investigation I discovered it's negative earth :(
So just for fun I tried the sender on the Smiths one and it is with 8 degrees all the way through the range so that will do for me.
On the theme of senders, all the ones I tried were the 5/8 unf size which is the usual Smiths type of sensor as fitted to most older type BLMC or whatever they were calling themselves at the time vehicles. The one that came from China was more like the old Ford Escort crossflow 1/8 NPT threaded style so just needed an adaptor to fit. I tried 5 different unf senders and they all gave the same wrong readings so I am totally confused with what is happening but now have a gauge that is near enough to do the job.

Ray White
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Re: Water temp gauge

Post by Ray White » Fri Jan 03, 2020 3:08 pm

If the gauge is negative earth, can't you simply switch the wires round so it is fooled into thinking it is.?

JohnW
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Re: Water temp gauge

Post by JohnW » Mon Feb 17, 2020 2:39 pm

Ray White wrote:
Fri Jan 03, 2020 3:08 pm
If the gauge is negative earth, can't you simply switch the wires round so it is fooled into thinking it is.?
Unfortunately not. The gauge has three terminals, +ve, -ve and sender, the case is plastic. Could probably do it if you took it apart and swoped the wiring internally. I did briefly investigate this but I very much doubt you could get it apart without destroying half of it - remember this is a £6 Chinese job so not designed to ever be taken apart unlike a Smith item.

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