Instrument woes

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

#11 Post by Alec » Sat Sep 26, 2015 6:51 am

Hello Kieran,

at the sender there is another wire which is for the low fuel warning light (plus a black earth wire).
The sender wire is green/black and the warning lamp is white/green. Disconnect both and check again. If your gauge is still reading half then there must be a problem with what is connected to the gauge, firstly check what colour wire it is, light green is the feed so the other wire should be green/black. If it is, disconnect that wire from the gauge and it should now read empty when powered. My guess is that the wrong wire is connected to the gauge (Possibly a lamp as Mike suggested earlier?

Alec
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KieranEbbett2500
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Re: Instrument woes

#12 Post by KieranEbbett2500 » Sun Sep 27, 2015 3:28 am

Hello again Mike, Alec and whoever else who has been following. I did as you said and it read 0. So I changed the voltage stabilizer and the temp gauge then read correctly but the fuel gauge went off the scale and past full. So I changed the sender and then that didn't do anything so I reconnected the original one and then had a brainwave moment and remembered that the insides of the temp gauge are the same as the fuel etc so dug out a tc combination fuel temp volts gauge and connected the temp one... nothing happened! So as a final attempt I connected the other sender to the wiring and set it to read full, turned the ignition on and it the gauge moved and read hot! So I dismantled the fuel gauge and the spare tc gauge changed the bits around and had a working fuel gauge again!
But it will only read 3/4 when full so I am on the lookout for a working S fuel gauge. So if anyone has one they'd be willing to part with then id be keen to hear from you.

Thank you for all your help.

Kieran

Simon2000
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Re: Instrument woes

#13 Post by Simon2000 » Sun Sep 27, 2015 7:18 am

Have you checked the voltage stabilizer is kicking out an ave 10V? I just swapped my failed one out for a new electronic one and its just failed only giving out 6v..
Found this info, so might make my own, can get all the bits to make 10 of these for less than £10! from CPC http://www.mgb-stuff.org.uk/saga11.htm

Update, you can do it for less than a £1 with this http://cpc.farnell.com/stmicroelectroni ... dp/SC08361
http://www.thelotusforums.com/forums/to ... regulator/
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Mike Stevens
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Re: Instrument woes

#14 Post by Mike Stevens » Mon Sep 28, 2015 12:05 pm

The gauges can be adjusted but I would suggest only after checking that everything else is correct first.

In the back there are 2 small cork 'discs'. If you extract these you will find a notched lever which can be (very gently!) moved. There is one for '0' reading and the other for full-scale reading. These can be set using a good fuel sender set to empty (set the 0 adjustment) and then full ('full' adjustment). These 2 settings might be a bit inter-related so adjustments back and forth might be needed. Also remember that the movement is a bi-metallic type so the readings can be different when going up the scale as opposed to when going down the scale - due to the 'sticktion'. It can be done though.

I have set the fuel and volt gauges this way before, using an adjustable bench PSU for the voltmeter. The temp gauge is a bit more difficult without knowing the real resistance/temperature characteristics of the original temperature sender! When I bought a new temp sender from Chris, I did characterise it with a DMM and saucepan of water on the hob. There is a picture of me doing it somewhere!

Electronic stabilisers are available via email and should just plug it. You can of course make your own as already said. A 7810 should be cheap enough but you may also want a couple of capacitors of around 1uF as the 3-terminal regulators do have a habit of 'hooting' without them.

What do I have in my cars? The old mechanical types!

Cheers,
Mike.
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