Fuel dash voltage regulator working?

Fuel gauge lever remains stubbornly out if site

40 ohms from tank sender

Voltage regulator enthusiastically regulates but is it ok?

on turning key I get 12.4 volts at gauge then it drops almost immediately to 2 then close to zero then 5.6 then 4.24 then 2 then another voltage - it nevers stabilises?

So is it broke?

 

If you've got a vibrator type regulator, the voltage on the output will bounce up and down.

Does the resistance on the sender wire (disconnected) change if you put more fuel in the tank?

 

Yes I have about 8 to 80 before I fitted the sender

 

So you've changed the sender in the tank?

 

No when I painted the fuel tank it I checked out that the old sender worked before putting in baffle and engine

on building the dash I checked the ohms on the brown sender wire - I get 43.9 just now

 

Those values sound more or less right. You've got the earth wire on the sender, yes? Measured the resistance with the sender in place at the dash end of the cable?

Might possibly be the regulator, then. I did knock up a few replacement ones, if you're interested and I've got any left.

 

Yes measured at dash cable detached. Tank earthed. New harness.

 

And the gauge worked previously?

 

Yes - be it a 4 year restoration in a dry double garage

 

The stock regulator produces pulses of 12 volts at a rate of one or two a second. Digital meters measure the average voltage for 1/3second, so basically any reading from 12 volts to 0 volts will show. It's all to do with digital sampling. If you hauled out a meter with a moving needle you would see it regularly bouncing ticking like a clock.
The average value over a long time should tend to about 5 volts.. means the regulator is working.

Is there a measurable resistance across the gauge terminals with one of the wires (sender or regulator) disconnected . This should also be a few ohms.

If it's very high resistance you might have a broken wire in the gauge or a bad connection to the resistance wire. In any case you are now in the "difficult" zone where it is theoretically possible to fit new nichrome wire but in reality almost impossible. When mine fails I will be out there with the micrometer to measure wire diameter and then a roll of nichrome wire of the correct gauge and a determined expression and an afternoon to waste. Then I will give up, 3D print a bracket for a GM stepper motor and write firmware for my microcontroller board I bought for the purpose of making a controller for the replacement of the fuel gauge.

 

If I get some more bits in, I could do you an adjustable regulator, which may solve your problem. PM me if interested.

 

I get 13.6 ohms across gauge, I can alter the ohmage from the tank, and shall trial a cheapie Chinese regulator I ordered before this thread to eliminate that next

 

There is that one where you install the fuel gauge sender with the arm jammed against the side of the tank so its stuck wherever it got jammed. If it goes in pointing left and you turn it clockwise to lock into the tank, it will jam.

So does the sender resistance change after a fill up of fuel ?

 

.

 

I`m wondering if i can jump in here, i have a similar issue with my bus, if i fill the tank to max the needle goes to full then as the fuel goes down to about half tank the gauge needle starts to bounce , the gauge needle bounces along the gauge sometimes dropping absolute zero for a while then to half tank and lower as the fuel is used.
I've had the dash off a few times but never found a regulator, [not that i know what i am looking for ].
Any ideas please.

 

Is there a small silver box screwed to the back of the instrument pod?

 

not that i remember, i took the dash off to find the regulator after looking at one on a suppler page , but nothing there.

 

What year is your van? Have you got grey or black instruments?

 

i wonder if at one time someone removed it and ran the wire direct [ i know nothing about electrics ]

 

my van is an early 1973 so has a mix of both , but the centre of the gauge is grey