Packard Forum Index » Post-War (1946-54)

On a '48 327, does anyone know the correct procedure to test the oil pressure gauge and sending unit? Is it simply to ground the wire?

Never mind- found it here:
https://www.packardinfo.com/xoops/html/downloads/SC/SC-VOL20NO9.pdf

Those checks will determine functionality but not accuracy of the gauge, I'd suggest that after you get it functioning reliably you check it's accuracy against a bourdon tube-type mechanical gauge so you know what true pressure corresponds to what position of the needle.

Good idea. I had attached a mechanical gauge, but it was in the engine compartment. I couldn't see it while driving. I put the original sending unit back, but it's a little disconcerting driving around with zero showing on the dash.

That particular sender may be a vendor only item if they still have any or maybe the instrument shops can repair them. The 48-50s used gauges and at least a gas sender which are a bit different than earlier and later models. I don't know if that oil sender has an actual resistance range or if it works like the gas sender with a heater making a bimetal strip switch a contact on and off. Fuel level affects the speed and frequency of the on/off cycle for the gas and maybe if oil is the same type sender, pressure would do the same.

A poster on the PAC forum seems to have made a universal GM 0-30 ohm resistance sender work for the gas but don't know if anyone has tried anything for oil. Also haven't heard feedback on how the gas sender is functioning. The gauge bimetal element is in series with the sender and if it never sees the on/off action and does not periodically get to cool I'd have concerns if it will be damaged or inaccurate. .