Hello all,
Looking for some help getting an oil pressure gauge working correctly in a '67 Mercury. The issue is that the original pressure sender delivered a resistance range of roughly 10ohm - 100ohm (100ohm = low oil pressure, 10ohm = high oil pressure) to the gauge, but the aftermarket senders manufactured today operate over a much larger range of resistance and pressure. So, for instance, where 40psi of oil pressure with the original sender would equate to 30ohm of resistance, the same 40psi with the new sender equates to 100ohm of resistance. These numbers are not 100% accurate, just examples to explain the issue. I know the gauge is good because grounding the sender wire pins the gauge at max oil pressure and this seems to be common issue in cars from this era when searching online about it.
So what I'm looking for, if possible, is a 12volt circuit that will take a resistance level and reduce it by half (or there about). I'm not looking for complete accuracy here at the gauge so don't worry about all the data and testing that would need to be done for that, I simply want the gauge to read an acceptable psi while the engine is running. I've hooked up a mechanical oil pressure gauge and know that the engine produces between 40 and 50psi of pressure under normal operation. With the new sender the in-dash gauge reads just under 20psi when the engine is cold and basically 0-5psi when the engine is warmed up.
I'm pretty green when it comes to circuitry and components but do have some experience assembling and repairing circuits so I should be able to follow some basic instructions. Or maybe there's something off-the-shelf that would achieve this. Any help is appreciated.
Thanks,
Paul
Looking for some help getting an oil pressure gauge working correctly in a '67 Mercury. The issue is that the original pressure sender delivered a resistance range of roughly 10ohm - 100ohm (100ohm = low oil pressure, 10ohm = high oil pressure) to the gauge, but the aftermarket senders manufactured today operate over a much larger range of resistance and pressure. So, for instance, where 40psi of oil pressure with the original sender would equate to 30ohm of resistance, the same 40psi with the new sender equates to 100ohm of resistance. These numbers are not 100% accurate, just examples to explain the issue. I know the gauge is good because grounding the sender wire pins the gauge at max oil pressure and this seems to be common issue in cars from this era when searching online about it.
So what I'm looking for, if possible, is a 12volt circuit that will take a resistance level and reduce it by half (or there about). I'm not looking for complete accuracy here at the gauge so don't worry about all the data and testing that would need to be done for that, I simply want the gauge to read an acceptable psi while the engine is running. I've hooked up a mechanical oil pressure gauge and know that the engine produces between 40 and 50psi of pressure under normal operation. With the new sender the in-dash gauge reads just under 20psi when the engine is cold and basically 0-5psi when the engine is warmed up.
I'm pretty green when it comes to circuitry and components but do have some experience assembling and repairing circuits so I should be able to follow some basic instructions. Or maybe there's something off-the-shelf that would achieve this. Any help is appreciated.
Thanks,
Paul