fuel sending unit melted on inside! what caused it ???

[jprather]

has anyone ever had a fuel gauge sending unit melt on the inside ??? what would cause this ?? any idea's ??? the yellow plastic piece should be solid !

this was a brand new unit in a brand new tank, I had posted the fuel gauge was all over the place, then quit. fuel gauge all of the place 72 charger

 

[BeepBeepRR]

Voltage regulator problems? Or possibly the Voltage limiter on the back side of the cluster. But it would have to be a weird short for the limiter to put out 12 volts. Should be 5 volts fluctuating.

 

[kiwigtx]

My guess is that something happened in your dash wiring to send 12 Volts to the sender, and consequently burnt the windings.

 

[kiwigtx]

My guess is that something happened in your dash wiring to send 12 Volts to the sender, and consequently burnt the windings.

^^^ just check your grounding connections also - if the ground has a resistance to it, then the current will increase, and that current will pass through the windings of the sender unit also. That will cause the burn.

 

[jprather]

Ol, I'm getting 12 v at sending unit wire non fluctuating, I get 12 volt fluctuation on my satty

 

[Don Frelier]

^^^ just check your grounding connections also - if the ground has a resistance to it, then the current will increase, and that current will pass through the windings of the sender unit also. That will cause the burn.

Perhaps this is poorly worded but it doesn't make any sense to me.

I = V/R

Maybe give it another try?

 

[kiwigtx]

Perhaps this is poorly worded but it doesn't make any sense to me.

I = V/R

Maybe give it another try?

What I was trying to get across was that it is possible to have a resistance in between the ground (chassis or battery terminal) and the other end of the ground wire where it attaches to the sender or tank etc.

That resistance will add to the circuit current.

 

[jprather]

I don't show any resistance in bround, but will check it again, I'm confused on proper voltage. My 72 satty shows 12 volts pulsing, the 72 charger Is 12 constant. Others have posted should be 5

 

[kiwigtx]

I don't show any resistance in bround, but will check it again, I'm confused on proper voltage. My 72 satty shows 12 volts pulsing, the 72 charger Is 12 constant. Others have posted should be 5

What sort of meter are you measuring with - digital or analogue? (yes, that's how it is spelt)

 

[jprather]

Digital circut tester

 

[jprather]

I do have a ohm tester to check the ground

 

[kiwigtx]

Digital circut tester

Digital can be a bit 'airy-fairy' when testing a pulsing voltage - depending upon frequency of pulses (drawing upon my inner-Bob)

An analogue meter will help stabilise a pulse and show a more accurate reading.

Have you got access to an old brake light or similar to make a test light - with an actual 12 Volt lamp in it? That should light up when pulsing.
If you have only got 5 Volts, the lamp will be dimmer than normal.

 

[jprather]

I can grab or make a test light, but is 12 or 5 correct? I'm thinking 12 based on the satty

 

[kiwigtx]

I can grab or make a test light, but is 12 or 5 correct? I'm thinking 12 based on the satty

I don't know which one - they might have changed it - '70 is 5-Volts.

 

[Don Frelier]

The original voltage limiter is a pulsed 12 volt supply.
The square wave approximates a lower constant DC signal around 5 volts
The gauges have a bunch of averaging so you don't see the pulsing.
It's just a heated bi-mettalic spring that pulses.

 

[jprather]

ok, so im gonna order a new dash voltage limiter, hope it not to much of a pain in @ss to change !

 

[jprather]

since my satty has 12 v at sending unit also, I think it might be going bad also, all the gauges read high on it also and if its supposed to be 5 +/- that would account for it

 

[jprather]

question, I have removed the voltage limiter ( waiting on a NOS ) should i have voltage at the fuel sending unit or not with it out ?