Fuel Gauge Woes

[JJames]

I have been reading and messing around with my fuel gauge and can't solve it.

It reads full at all times. The needle is buried on the right. I have pulled the sending unit and cleaned it and checked the resistance between the spade terminal and the body. It reads about 250 at empty and about 20 at full.

When I put 12 dc volts across to the body it reads 12 volts at the spade terminal at full and at empty.

I have put the fuel sending unit lead to the temperature gauge (as a test gauge) and it goes all the way to the right as well.

I have ready many of the threads on this site and can't find a solution.

Any help would be appreciated!

 

[RootesRacer]

What model alpine?

The different models have different troubleshooting as the gauges are quite different.

If its an early one, I'd look to see if your gauge case is grounded.

If its a late one, I'd look for a short to ground somewhere on the sender wire.

 

[JJames]

It is a Series V.

I checked for the short in the wire. When the wire is disconnected from the sending unit the gauge does nothing, so not a short in the wire.

 

[George Coleman]

The gauges should have 9V across them thats if you are using the votage stabilizer under the dash.

 

[Jimjordan2]

I just finished going through this process. It turned out that the gauge terminals were grounding to the gauge housing. The fiber disc was missing under the spade terminal. The terminals have a very small area to be centered and not touch the housing. Just another area to check.
I keep learning that 95% of our electrical problems are Ground, Ground, Ground. Or lack of.

Isn't that supposed to be 10V George?

 

[JJames]

Thanks to everyone for the help. I really need it.

I am using the voltage regulator that supplies 10v to the fuel and temperatures gauges.

I'll check the gauge terminals, but my temperature gauge works fine and it is essentially the same guts as the fuel gauge and when I put the fuel sender to the temperature gauge it goes right to the top as well.

 

[RootesRacer]

Swap the fuel gauge so it connects to the water temp sensor.
If the gauge points where it would if it were a temp gauge then its not the gauge.

Also measure the resistance of the fuel sender wire (under the dash but disconnected from the gauge) to ground. See if the resistance matches what it should be if it is measured at the sender terminal.

 

[JJames]

We may have a winner. Connected the blue green lead from the temperature sensor (which is cold) to the fuel gauge and it went all the way to the right, the same as when connected to the fuel sending unit.

It appears it may be the gauge. Any leads on where to get a gauge looked at?

 

[RootesRacer]

The later gauges are bimetal thermal movements (works on heat).

Sounds like yours is broken or perhaps you have an early gauge installed?
Early gauge will move really fast compared to the sluggish later gauges.

If you have the correct gauge (and just connecting the sender doesnt somehow short that terminal to the case), its likley not reparable.

 

[Tom H]

James, couple things to check:
1) as Rootes noted, are you sure you have a late series gauge? You say it goes full scale when you connect either fuel or temp sender. Does it move, quickly ,like the blink of an eye? If so it is almost surely an early gauge- totally different than late series, which take several seconds to go to full scale.
2) with no sender wire connected at the gauge, can you wiggle/push the connector on the gauge to get it to read full scale? If so you probably have a similar problem to what JimJordan described in his reply #5.
3) send me an e-mail (click on my name at the top of this msg)

Tom