Oil Pressure Sender & Gauge Troubleshooting

[Jeremyrig]

I'm troubleshooting my 74-2F oil pressure gauge and am at a point where I'd like to know the expected ohm range for a warm motor at idle VS running RPM 2-3k? The current sender is reading about 10 ohms regardless of RPM and a new one I picked up from NAPA is sticking at about 35 ohms also regardless of RPM. Maybe an issue with the source connection but haven't hooked up a mechanical gauge to confirm....yet. Any help would be greatly appreciated!! The oil pressure gauge pegs when I ground it and I'm not opposed to attempting to calibrate it, just want to find out if I'm on the right track or missing something...

I'm seeing mixed findings on the forums with other series LCs so hoping for some advice that relates appropriately

 

[thebigredrocker]

BJ40green seems to be knowledgeble. You can search his posts

Here’s a thread he commented in: Oil Pressure Gauge?

 

[73tlcv8]

The oil pressure gauge doesn't really change resistance, it is a contact that opens and closes. This is a previous post I made when troubleshooting mine:

This is a bi-metallic regulator. As pressure increases the stationary contact moves closer to the moving contact on the bi-metallic strip. So, as pressure increases it takes more current through the heater wire to get the contact to open, thus more current through the oil pressure gauge. My gauge is a little sticky at the zero end so I was never getting enough current to move the needle. Grounding the oil pressure gauge wire was enough current to get the gauge to deflect but not getting enough through the sender. I pictured the sender as a variable resistor but it is a point type current regulator similar to the one in the fuel gauge. That's why the light blinks when testing.

 

[Jeremyrig]

BJ40green seems to be knowledgeble. You can search his posts

Here’s a thread he commented in: Oil Pressure Gauge?

Thank you very much and that makes sense. One realization I had is that I probably shouldn't be expecting a variable reading like a mechanical gauge and just having the gauge as an indication that things are nominal or not is the design intention... I think where I'm at is either calibrating the gauge by bending the needle so that it's starting point is at the low point rather than berried all the way to the left so that when it does register it's within the gauge range and visible. Or, taking apart the sender and adjusting it which seems more difficult based on the construction and pressed bell flange on the sender... What are your thoughts? Do you see downsides to adjusting the gauge itself?

Thanks again!

 

[65swb45]

Thank you very much and that makes sense. One realization I had is that I probably shouldn't be expecting a variable reading like a mechanical gauge and just having the gauge as an indication that things are nominal or not is the design intention... I think where I'm at is either calibrating the gauge by bending the needle so that it's starting point is at the low point rather than berried all the way to the left so that when it does register it's within the gauge range and visible. Or, taking apart the sender and adjusting it which seems more difficult based on the construction and pressed bell flange on the sender... What are your thoughts? Do you see downsides to adjusting the gauge itself?

Thanks again!

If the gauge is starting off outside the visible area of the gauge near the L, that is strong evidence that it has been shorted out at some point.

 

[Jeremyrig]

If the gauge is starting off outside the visible area of the gauge near the L, that is strong evidence that it has been shorted out at some point.[/QUOTE

Even if it's still moving?

 

[GA Architect]

......just having the gauge as an indication that things are nominal or not is the design intention... Thanks again!

> Click here < ....see post #17

The gauge is just an indicator.

 

[65swb45]

Yes