Fuel gauge problem/issue

[motherofgod]

My car has a separate fuel gauge, now I want to put/conect it to the original. now the old gauge is connected to(old wires) a little box at the top of the speedo, what is it? can I connect the wires that run my separate gauge straight to the gauge on the speedo, or do I have to run them through the mystery box, I've looked at my manual and it doesn't really say what it is!

Hope you can help

James

[bmcecosse]

It's a very basic voltage regulator - works on bi-metal strip basis - so the original gauge reads more steadily no matter the state of the battery/charging system. The feed to the original gauge needs to go through the volts reg. I think early cars with silver speedo had a simple gauge that does NOT use the volts reg - only the later black speedo/gauge has the volts reg.

[motherofgod]

Excellent, I'll have fun tomorrow! My speedo was black, now it's white!
I painted it to match the tacho

James

[motherofgod]

Ok I've wired up the gauge and its reading but not sure if it's reading correct or going down(with usage) It reads at the mo 3/4 full any other ways of testing it, other than emptying tank?

James

[Pikey]

Try taking the wire (green/black stripe) off the petrol tank sender and short it to earth. The gauge should then show a Full tank.

[motherofgod]

UPDATE, It hasn't moved much I'm wondering whether it's working! I've ordered a new white gauge to match if i don't have any joy

Pikey- Im going to try that.

James

[Willie]

Two possibilities. either the tank is not a perfect earth( try another part of the actual chassis) or you have the sender unit fitted wrongly. This can mean that the float hits part of the internals and cannot read full.

[motherofgod]

OK, I think I've solved it, as I said before it wasn't moving and reading almost full. I did what pikey said and nothing changed so I thought it wasn't wired properly so did a bit of testing and swaping and finally read a proper reading to what seemed to be in the tank. tomorrow I'll fill up and see what happens!

Thanks for your advice

James

[ozzy]

hello I am writing this for my son Ozzy It seams that he has this same problem, his fuel gauge does not work he has tried to re earth etc. but still no good . he has the three green wires on the side or the fuel gauge 1 wire has a electrical connector and looks like that there should be another wire there ? He is new to all this he only got the car 2 weeks ago. he is not here at the moment but I can relay messages to him or please ring his mobile on 07845886240 I hope that I have worded this all correctly please forgive me if I havent many thanks Ozzy's mum Julia

[Willie]

There should be three dark green wires on one terminal (marked 'B')
and one Light Green wire on the terminal marked 'I' (instrument) which goes to the fuel gauge. The terminals marked 'B' and 'I' are on the VOLTAGE REGULATOR which is attached to the back of the speedometer.
The wire on the other terminal of the fuel gauge is Green with a black stripe and goes to the petrol tank sender unit.

[ozzy]

I'm sorry I should have said that Elly May is a 1957 model and Ozzy says that he doesnt think that it has got the voltage regulator on it does this help at all ?

[ozzy]

ozzy has been speaking to a guy at a local yank car meet tonight would his car originaly have been posative earth originaly it is now negative could the fuel guage still be pos earth as the needle wants to go backwards thanks he is coming down to the vintage and classic car show at earls barton this bank holiday weekend anybody else attending let us know j10 a45.

[alex_holden]

The early gauges don't have a voltage regulator. The polarity doesn't matter - they work the same on either positive or negative earth.

Does the gauge show full if you disconnect the wire from the sender unit and connect it straight to earth?

[Welung666]

the needle wants to go backwards

Sounds to me like it's the later type gauge or sender.

[alex_holden]

the needle wants to go backwards

Sounds to me like it's the later type gauge or sender.

It shouldn't be on a 1957 car.

[ozzy]

Alex holden wrote :
Does the gauge show full if you disconnect the wire from the sender unit and connect it straight to earth.



this has been tried and it flicks to minus empty

[Welung666]

It shouldn't be on a 1957 car.

Shouldn't means nothing on a 50 year old car with X amount of previous owners! My 63 4 door 'shouldn't' have an alternator but it does!

[ozzy]

Can anybody send me a pic. of the back of the gauge so i can see what it should look like ?

[Willie]

OZZY, ok, on your model you should have the dark green wires all on one terminal of the fuel gauge since there is no voltage regulator. The other terminal of the gauge should have the green wire with a black stripe on it. This wire arrives at the tank sender unit (on top of the fuel tank) and should be connected on a terminal with a NUT. If it is connected with a PUSH-ON connector then it is the wrong (later) tank sender unit which will read backwards! You have already proved that the sender wire is ok to the gauge. You cannot overcome this by reversing any leads, you need the correct sender type.

[ozzy]

Hi its Ozzy's mum here again he says that he got the wires checked today and then the gauge went up to a quarter of a tank, he thought that it was sorted and put more petrol in tonight but it still reads a quarter of tank, its begining to get him down he is worried that he will run out of petrol (and no warning lights) we are all going to a classic car show this week-end so I hope that there will be someone there that he can talk to . thanks to all for your help.