Does anyone know what the resistance values (ohms) should be at different pressures on a 6 volt oil sending unit?  It is on a '55 ford y-block.  I measured mine while priming the oil pump and it read 9.6 ohms.

Thank you.

What car is this on?
If on a 55 car with the idiot light the sender is only an off/on switch to ground the light circuit.
The trip point usually is stamped on the pressure sender 5psi, some are higher.

If the sender is on a Merc with a guage the sender unit will have a resistance value.
Here is a link to a previous discussion on a sender unit . It was for a 12 volt guage package.
http://www.y-blocksforever.com/forums/Topic54159-3-1.aspx?Highlight=sender+unit

marv

 

Was this for a factory or aftermarket sender. Aftermarket, electric gage types will vary based on the pressure they sense. You'll have to contact whomever built the gage to find out.

Frank/Rebop

Bristol, In ( by Elkhart) 

The sender is a 6 volt unit on a '55 F250. I bought it used at a swap meet from Marv Tomlinson a few years ago.  The gauge (not a light) worked when the 239 was in the truck.  I am replacing the 239 with a 292 and was priming the oil pump and was curious what kind of oil pressure it had.  When I prime the pump, the resistance starts at infinite, then drop to 9.6 ohms and stays there.  When I shut the drill off, the resistance remains steady for a while then slowly increases to infinite again.  I am interested to know how accurate this gauge setup really is so I can keep an eye on the oil pressure.  It is a used engine.  I have attached a picture of the sending unit.  On the top, it has an arrow that points up.  On the bottom, there is a circle with the letters KS in it.  Above the circle there is a number 9 stamped in it.  The KS and number 9 are upside down with the arrow pointing up.

The KS would be for King-Seeley, an instrument manufacturer of that period.  The 9 is probably some kind of date code, don't know.  The reason for the slow bleed off of resistance is because there is a very small hole in the pressure passage to dampen out pressure pulses, so it takes a few seconds to drain the pressurized oil from the sender.

John - "The Hoosier Hurricane"

Look on the hex nut (or square area) of the thread part of the sender unit (where you would place a wrench to tighten).

You should see a stamped number such as 50 or 80, this is the pressure required to give you maximum deflection on your guage. If you guage is only deflecting to mid range then assume you have about half of the stamped pressure if everything is accurate. The best is to use a mechanical guage to confirm.

marv