Instrument woes

Batteries, Alternator, Wiring, Lighting, etc. (Please discuss ignition problems in the Engine category)
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KieranEbbett2500
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Instrument woes

#1 Post by KieranEbbett2500 » Mon Sep 21, 2015 6:45 am

Hi. I am new to the forum but have owned a triumph for a few years but have an issue that I have no idea about.

My fuel gauge reads half a tank as all the time regardless of whether the sender is even connected and regardless of the level of fuel. The temp gauge no longer reads. But that has only happened as a result of my tinkering... I have checked all of the connections which all seem fine and as far as I can tell is wired up as per the wiring diagram. The car is a 1977 2500TC but has S gauges which uses a modified tc wiring harness for the gauge cluster. I have tried a different sender, tried plugging in a TC gauge which didn't work. Tried another voltage stabilizer which didn't help either.

Any suggestions or things to try would be great as I have not a clue.

Also when on main beam the indicators have an issue instead of the correct light on the cluster illuminating the opposite one does and the main beam also flashes with it.

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Re: Instrument woes

#2 Post by Alec » Mon Sep 21, 2015 8:42 am

Hello Keiran,

did the TC gauge also read half full when you tried it?

You can try and see what happens when you disconnect the sender wire from the gauge and it should read zero with the ignition on, take a bit of wire and connect to the gauge sender terminal and touch that wire to earth and the gauge should read full. If neither happens the gauge is faulty.

Your indicator tell tales are obviously crossed but where is an easy place to correct it I couldn't say, you'll have to trace the cables but I suspect most terminations will be moulded plugs so you may end up cutting and soldering the appropriate cables? Check your instrument earthing is sound as that may be why the main beam is flashing, i.e. the indicator tell tales are earthing through the main beam indicator.

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Re: Instrument woes

#3 Post by KieranEbbett2500 » Mon Sep 21, 2015 9:15 am

Thanks Alec.
I can't actually remember what it did I will have to have a look tomorrow. It first began with the gauge just not working which I thought was a broken wire but I replaced it and had these issues.

The main beam problem has only occured since the fuel gauge has been strange. The indicators work perfectly on dip or without the headlights. So I thought a common fault? I don't know
Which of the wires is from the sender? I assumed it was the wire not from the voltage stabilizer.
Thank you :)

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Re: Instrument woes

#4 Post by Alec » Mon Sep 21, 2015 11:07 am

Hello Kieran,

I forget what colour the sender wire is but the feed should be a light green wire from the voltage stabiliser. I also don't remember if the instrument's terminals are marked which would mean the instrument is sensitive to correct connection, I suspect that it is, something else to check?

Alec
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Re: Instrument woes

#5 Post by Mike Stevens » Mon Sep 21, 2015 11:51 am

The instruments are all hot wire types that heat up a bi-metallic strip which then bends to give the dial reading. As it's just a heating effect, it doesn't matter which way round you connect the gauges! I have a theory that they are all the same inside, with only the front dial changed to read volts, fuel or temp!

Alec is right about testing the fuel gauge, the only thing I'd say is that if you don't get zero/full readings with the sender disconnected and then the wire connected to ground, the fault may not be the gauge.

If you have a voltmeter of some sort, you can measure the output of the stabiliser. The original types give an average of ~10V but the reading wobbles up and down around 10V. If you see something like that, then the stabiliser is probably OK. Modern replacement ones are electronic and should read a steady 10V.

You say that the gauge reads half all the time - is this with the ignition off as well? If not, I suspect that you have got some wires crossed and the gauge isn't connected to the sender but maybe to a bulb somewhere?

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Re: Instrument woes

#6 Post by docwad » Mon Sep 21, 2015 11:52 am

it will most likely be the voltage stabiliser, (solid state ones are available or easy to make ) or possibly the night dimming relay as this can affect lots of things try disconnecting its earth wire and see what happens
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Re: Instrument woes

#7 Post by KieranEbbett2500 » Wed Sep 23, 2015 2:39 am

Hi all. A very good friend of mine has helped me with the indicator problem we found there was a stray earthworm which had come stray so with that repaired things were allgood there. However our tinkering could not solve the issue with the fuel gauge. Once I have consumed some of the fuel in the tank it should be pretty full we will change the sender for yet another and try another voltage stabilizer.

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Re: Instrument woes

#8 Post by Alec » Wed Sep 23, 2015 9:21 am

Hello Kieran,

would you confirm that the instrument reads half full all the time, as you say, regardless of if the sender is connected, does this include when there is no power to it?
Also where is the sender disconnected from, tank or gauge end? It should be the gauge end to give a real test.

Alec
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Re: Instrument woes

#9 Post by Mike Stevens » Wed Sep 23, 2015 11:59 am

As Alec says, before changing yet another sender, do the gauge check - 0 with nothing connected, full when the sender wire is connected to Ground.

I agree with Alec in that a test at the gauge will test the system up to the gauge (including the stabiliser) and if repeated at the tank end will also check the wiring to the tank.

Cheers,
Mike.
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1971 2.5PI Saloon Sapphire blue
1973 2.5PI Saloon rust some Honeysuckle
1973 Stag French blue
(1949 LandRover was blue should be light green!)

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Re: Instrument woes

#10 Post by KieranEbbett2500 » Sat Sep 26, 2015 1:43 am

hi again,

the gauge reads only when the ignition is switched on. I unplugged the wires from the sender and it was still reading half. as I understand the wiring is all correct how could I test the wiring up to the gauge as you have mentioned.

thanks again Kieran

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