Fuel gauge not working.

[Bremar 2]

Hi, I have a 1993,  1.9i Gentry. I have looked through this forum and elsewhere, but can’t quite find the answer to testing the function of the fuel sender in the fuel tank and fuel gauge. 
As per guidance on this very good site I have determined that 1. The yellow/green earth wire is properly earthed. 2. That the white incoming lead is reading 12 volts but that  3. The blue lead gives no voltage reading. 
My 3 questions that I would like help with are:

 1. I think I’m supposed to get at least some voltage from this blue wire connection which then informs the fuel gauge of the level inside the tank yes/no ?

2. What if I artificially applied 12 volts to this blue wire. Should I get a full reading on the fuel gauge itself to confirm that that is at least working or will this damage it? 
3. how else can I test the fuel gauge itself if not 2 above? 
I’ve attached a link to a YouTube vid to help identify my issue. 
thank you in advance. 
Bremar. 

 

[Tom Fenton 1,542]

There are thee connections to the sender unit as there are 2 circuits. One is a resistance loop to the gauge so a varying resistance makes the gauge display. The other circuit is a low level switch that turns the warning light on. I haven't got a wiring diagram to hand, but they are available in the Haynes manuals as well as elsewhere.

[Bremar 2]

  

Ive got the Haynes manual. Fuel sender unit is no44. M65 is earth ( so the green yellow wire) either 65 or 65a are white or blue. (But couldn’t see numbers on wires ). 

Would it be 65 or 65a bringing power in?  Either way how do you test the sender in situ. 

Thanks for the help so far 

Bremar. 

[Tom Fenton 1,542]

Neither of them bring power in. The one showing 12v is probably the warning light wire as there will be 12v on the other side of the bulb. When you earth it the light should come on.

 

65 is a variable resistance to earth that operates the gauge

65A switches to earth to make the low level warning light come on

 

With the ignition on and a helper watching the dash earth the white wire and then the blue wire. One should make the light come on. One should make the gauge read I think full.

 

The wiring is usually OK and its probably the sender is duff.

 

[petert 586]

Forget the 12V, you need to measure resistance, with the plug disconnected. I think the range is 40-200 ohms from memory. I that checks out, then you have wiring issues. You could also replace the sender with a 100 ohm resistor to verify the gauge is working. ie 65 and earth.

Edited September 11 by petert

[welshpug 1,657]

I've had one instance where a mouse or two had made a home in the glovebox and nibbled the fuel level sender wire in the corner above the fusebox, didn't take too long to find really.

[Bremar 2]

All together that is really helpful information and really appreciated. Hopefully if I get time tonight when I finish work I will action it and I’ll do a youtube vid as backup it up. I will update when I can. 
Apart from a wheel shake (even though I have put 4 new balanced tyres on the car) it’s very impressive. Not quite the GTi’s you guys have got but the Gentry a super car. 

[Bremar 2]

So success then failure then partial success. 
Earthed blue wire at sender end. Fuel gauge went t to full so success and pointed to fuel sender as issue. 
i removed sender and dismantled it and found the spring wire inside had come away from soldered joint. Re soldered it and put it back in, but fuel gauge dIdn’t appear to work. Took it back out and manage to break spring some more. Did botch repair and put it back in thought it still wasn’t working but left ignition on while i tidied up. Then saw it was showing third full. 
i think I had repaired it the 1st first time but was too impatient and didn't realise how long it would take to register. Ive sent away for a new one. I done a  youtube video with link below.

Thanks everyone. Bremar. 

Edited September 12 by Bremar
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