Oil Pressure Guage question

[BAYDOG]

Ok , I know it is just an idiot guage, but mine always reads at the max, once in a blue moon , on a long drive it will come down into the normal range. My guestion is.... when I turn my engine off, and put the keys in my pocket, it stays at the top. Is it suppose to come down to the bottom like all the other guages?? I replaced the sender on the engine, and maybe this summer will put in a actual Mechanical Guage. Where does your guages read with the ignition turned off??

 

[yob_yeknom]

The guage itself must be bad then. It should drop all the way down with the engine off.

 

[BAYDOG]

Thats what I thought. Thanks for the speedy reply. It's just one of those things that drives you crazy.

 

[Opera House]

Thes gauges work by

balancing the magnetic fields of two coils at 90 degree angles to each other. One coil is powered with the full voltage and the other through the resistor on the back of the panel and the sender switch. For it to go full scale it probably means that the powered coil has an intermitant connection that opens or the ground on the instrument cluster is bad. Do you notice lights dimming or jumps in the other gauges.

 

[BAYDOG]

Not on the dash, but I do notice a dimming or flickering of the headlights once in awhile??

 

[Maniak]

There is another possible cause... You may have a short in the wire that goes from the sending unit to the gauge.

The harness where the oil sender is on our '92 looked like play-do (sp?).. as in all the wires got hot and melted together, and they were all shorted to each other.. (one of them must have been close to ground)...

Once I fixed that, my oil gauge read back in the middle...

Easy way to test it... have someone wiggle the wires while the truck is running and see if it drops.. if it does, you have a short.. if not, the gauge could be bad...

edit
I just thought of something.. Unless you have done the oil pressure gauge mod, your sending unit only has 2 positions.. open (@ <5 psi) and closed ( @ > 5psi).. When it is closed, it is shorted to ground and it relies on the 20ohm resister on the back of the gauge.. This means that it isn't a short in the wire from the sending unit to the gauge... It must be in the gauge (or the PCB behind the gauge).

~Mark