oil pressure gauge has stop working. put a new sending unit on,that didnt work. checked the back side of the cluster and didnt see anything unplugged or out of place.

when you turn the key on it will go to the middle of the gauge as soon as the truck starts it goes straight to no pressure at all.

is this a bad gauge or wiring?

 

Take the wire off the sending unit.
Turn on the key.
While the gauge is viewed.
Short the wire to ground.

The needle should go from from no pressure to the center of the gauge when the wire is grounded.
If it does that then the wiring and the gauge are fine.
You would then have a bad sending unit or engine.

 

forgot to say this is the 2nd sending unit that we put on and still nothing

 

ok switching gears,

my voltage gauge is dancing around now. would it be a bad cluster?

my oil gauge doesnt work. my temp gauge some times goes up and down at times then stays in the middle, and now my voltage gauge is dancing around. also my fuel gauge doesnt work either. could it be a bad cluster? what controls the cluster?

 

It would be nice to know what we are working with.
But sounds like more of a bad ground (body ground).
Could also be a bad voltage regulator on the back of the cluster.



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what do you mean bye (nice to know what we are working with)?

its a 92 f150 e40d 5.0l

 

It makes a big difference on how we answer the question when know what type truck it is.
As you can see I guessed wrong as I posted a photo for a 1985 truck.

Now I would go back to say it was is a bad body ground.


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Hey sub you got that backwards bud. Open circuit should produce a zero reading on the gauge. Dead short to ground should swing the needle to mid-scale.

 

i have cleaned that already still nothing. yea my bad on that. sometimes i forget. i knew that was from a 85 cause i own an 85 f150 4.9 3spd also

 

Yes it is backwards. When the pressure goes up the switch grounds the wire.
I had it right the on the first post and I talked myself out of that way and when back and changed it.
Thanks.

 

And check that the wire is good from the body to the NEG post of the battery?

 

from what i could see, its night here now, ill take a closer look at the wires in the moring.

 

ok tested the gauge today,so going to buy a new sender soon

 

Note that the sender is an off & on switch.
When the oil pressure gets above 5-7psi the switch makes the circuit to ground.

Oil Pressure Gauge and Oil Pressure Switch
The Oil Pressure Switch controls the magnetic Oil Pressure Gauge's pointer position. The Oil Pressure Switch closes under normal engine operating conditions; the Oil Pressure Switch opens with the engine off and no oil pressure.

 

you can push it to the floor slow and it never moves