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Dart Temperature Gauge

rogerharrop
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Dart Temperature Gauge

Post by rogerharrop »

Hello,
Over the winter I had the dashboard off and sent all the instruments to JDO for service/recalibration. The problems I had with the speedo and the rev counter are sorted but the temperature guage which used to give a rock solid reading now twitches (up) all the time. Any ideas please?

Many thanks
Roger

classiclife
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Re: Dart Temperature Gauge

Post by classiclife »

Hello Roger,

I presume you sent the oil and fuel gauge as well ?? Are they behaving as per removal ??

Have you spoken with John Ostick about the issue and if so what did he say - think I can guess his response.

My only thoughts are that perhaps the transmitter is starting to play up or the voltage stabiliser is starting to do so. A common issue on instruments playing up can be an earth connection which I presume is possible on fibreglass cars.

Not much help, I'm sorry but just a couple of ideas.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

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migray
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Re: Dart Temperature Gauge

Post by migray »

I would suspect a poor earth at the gauge. There is no voltage stabiliser on the dart but each instrument needs its own earth wire.

classiclife
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Re: Dart Temperature Gauge

Post by classiclife »

Thanks Mike, that is useful to know.

Just out of interest, is that because the SP is fibreglass or other reasons ??

At least Roger can knock one of those suggestions off the list !!

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

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Ian Slade
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Re: Dart Temperature Gauge

Post by Ian Slade »

It's a Dart/SP250 the oil pressure gauge is a mechanical one, no electrics and no voltage stabilizer, the fuel, temperature and ammeter can all be easily calibrated by adjusting the coils, two screws on the rear of the instrument/gauge are loosened and moved in the slots this will change the needle position. Can be quite therapeutic on a winters evening with a 12v supply and the transmitters :lol:
The only earth on the temperature gauge is at the sender casing which screws into the engine, check the engine earth strap, however if one or both screws holding the coils are loose on the rear of the gauge, this will cause the needle to move with vibration.
Owner since the 70's, Genghis is slightly to my left.

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migray
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Re: Dart Temperature Gauge

Post by migray »

Yes the earth is only needed at the gauge for the bulb which illuminates it, so it shouldn't affect the reading. All the gauges need an earth for the bulbs though.
The sender does need to be earthed however so check it hasn't been partially isolated somehow. The 12v line does connect directly to the gauge so check that is a good connection.

rogerharrop
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Re: Dart Temperature Gauge

Post by rogerharrop »

Many thanks All,

I've now heard from John Ostick (he'd lost my email) and he also suggests it's the earthing.

Roger

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JohnM
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Re: Dart Temperature Gauge

Post by JohnM »

Just my 5pworth, but the temp gauge fitted to my SP is a Smiths "Wheatstone Bridge" type unit, so it doesn't need a voltage regulator, but it definitely needs a good earth to the gauge to work properly.

I don't know it would cause jerkiness, but I do know it causes it to read wrongly if the earth wire comes off (guess how I know!)

Hope you sort it out, whatever it turns out to be,

John
John M in Middlesex, NW London
1962 SP250 "B" Spec
DLOC Herts Region Sec

rogerharrop
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Re: Dart Temperature Gauge

Post by rogerharrop »

Sorted! - it's now rock solid. Just needed the earth from the gaugue

Many thanks all

Roger
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heh101353
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Re: Dart Temperature Gauge

Post by heh101353 »

Hello,

The fuel gauge and temperature gauge of my SP always change the reading when another load becomes active.
When turning the headlights on for instance the fuel gauge shows less fuel than before, the temperature reading goes up.
As soon as the additional load is switched off both gauges go back to where they've been before.
No a big deal as the reading does not change dramatically. The deviation is around 10°.
It's been like this ever since I own the car.
My SP is equipped with an electric radiator fan which has to be switched on or off manually, no automatism there.
When the fan is switched on, the fuel gauge reading goes down the usual amount. But the temperature gauge jumps to the limit stop beyond the 230° marker.
Tapping on the glass may persuade the needle to fall back a bit but not to a reasonable extend. Switching off the fan will not help either.
Normal operation of the gauge is only obtained by turning off the fan and ignition. Adding a hazard flasher was the only change to the electrics in the recent past.
There is no voltage stabilizer installed.
Any ideas, please?

Thank you
Hans
:o owner since 2015 :mrgreen:
https://www.wyhe.ch/

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