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Dart Temperature Gauge

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rogerharrop
Posts: 41
Joined: Sat Nov 17, 2018 11:54 am
Location: Watlington, Oxon
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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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Location: Ridgewood - East Sussex
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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 Area Representative.

Southern Classics Society Events Co-ordinator.
www.southernclassics.org.uk

migray
Posts: 164
Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

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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Joined: Wed Sep 05, 2018 9:55 am
Location: Ridgewood - East Sussex
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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 Area Representative.

Southern Classics Society Events Co-ordinator.
www.southernclassics.org.uk

Ian Slade
Posts: 531
Joined: Sat Feb 13, 2016 9:54 am
Location: Scotland

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.

migray
Posts: 164
Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

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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Location: Watlington, Oxon
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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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Location: N W London

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

rogerharrop
Posts: 41
Joined: Sat Nov 17, 2018 11:54 am
Location: Watlington, Oxon
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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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