• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Austin Healey Fuel Gauge

Share this page

N

neophyte

Freshman Member
Offline
I have an 1958 Austin Healey BN6.

The fuel gauge reads empty all the time. The grn/blk wire from the sender to the gauge reads zero ohms when detached at both ends. The grn/blk wire reads 5 volts when attached to sender and gauge. The double green wire reads 12.3 volts when either attached or detached from gauge. When the sender is removed from the tank with one test lead attached to the body of the sender and the other attached to the post on the sender readings of 10 to 80 ohms occur when the float is raised. The tank is about 1/4 full.

I don't know what the voltage readings are supposed to be and it seems that the new sender is working properly. Does the fuel gauge need work? If so instructions on how to disassemble, inspect and repair would be helpful.
 
It's not that the fuel gauge "can't" be taken apart, but it really isn't suited to DIY repair; you'll discover this (as I did...) as soon as you loosen those tiny nuts on the back.

The fuel gauge is actually a volt meter, with a funny scale. By rights, shorting the signal wire from the sender to ground should show full scale on the gauge. If it does, it's working.

I sent all my gauges to Nisonger Corp last year, and with the exception of the speedometer (fault is in the xmsn) they all work great.

What's the VIN of your two-seater? Mine is BN6L-942.
 
Here you may find a lot of info gauge and wiring are the same with very little difference

https://mgaguru.com/mgtech/electric/fg104.htm

this is the troubleshotting but tere are also others articles a test insrum. to controll the gauge
etc.
<span style="font-weight: bold">BEFORE</span> please controll the <span style="font-weight: bold">SENDER GRAUND</span>
 
Randy,
By shorting the sender wire to ground the gauge still registered empty. I guess the gauge needs work?
My VIN is BN64642.
 
Be sure and check the meter's groundunder the dash as andrea said.--Keoke
 
To test the sender unit use an analog ohm meter (swinging needle type not digital). Disconnect the wire from the sender unit, connect an ohm meter from sender terminal to ground, set meter on 100 ohm scale, and shake the car. Depending on fuel level, the meter should read somewhere between 0 ohms (empty) and 70 ohms (full). When fuel sloshes and the sender float wobbles up and down the needle on the meter should waver gently in harmony with movement of the float. If meter needle movement is jerky or eratic, the sender unit has intermittent internal contact, needing to be rebuilt or replaced

Fuel Gauge
In Schematic form it is obvious that the variable resistance tank sender unit is wired in parallel with the right gauge coil. When the tank is empty at zero resistance it's clear that the right side coil is shorted out and will carry no current, so the left side coil pulls the needle into direct alignment with the "E" mark on the gauge. As the tank sender unit resistance increases it forces some current to flow through the right side gauge coil which pulls the needle to the right. At the same time the total circuit resistance is increasing, so the total circuit current is dropping, and the left side gauge coil is losing some of its strength. When the tank is full and the sender unit is at maximum resistance the gauge needle should be pointing directly at the full mark. Moving the magnets to different distances from the gauge armature changes their pull, so there is a means to calibrate the instrument
 
Andrea, I did your test with the analog ohmmeter and the sender as you suggested but my low ohms scale goes to 2K which probably wouldn’t be sensitive enough to show any swing of the meter needle. The info in the link you supplied is very educational.
 
Thanks to all that offered assistance, I found a poor ground on the sender and thanks to the link that Andrea supplied I learned a lot and was able to re-
solder a broken wire in the gauge. Not a job that human hands should be doing. Those wires are miniscule and easily broken but I managed. Thanks again!!!!
 
Back
Top