Oil Pressure Sending Unit BO - Hepl

Dads41SuperDeluxe

Dads41SuperDeluxe

Member
'41 passenger - 6V pos ground - I am having problems getting a working Oil Pressure Sending Unit. My last one, made in China, went bad. I ordered a new one from DC. Tested ohms when I got it. 11 ohms on the bench. Installed it. It registered about 10 psi with engine off and ignition on. When I started the engine, it did bump up but did not register correctly. I have checked with the pressure with a reliable mechanical gauge. When I shut the engine down and with ignition back on, it registered about 5 psi and 5 ohms.

Just got a replacement from DC (China) and its registering 11 ohms on the bench just like the last one.

I assume these work on resistance. Do I have two bad sending units?
 
They don't work on variable resistance, at least the original ones.

You can test the gauge in the dash by connecting a 1.5v battery (C or D cell) across it. It should read 1/2 scale.
 

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Do you know that there were two sending units, a 50# and a 80# yours should have the 50# to correspond with the gauge, 1942 and up took the 80# sending unit. This would make the gauge read wrong.
BILL
 
bobwellsnoveltyshop said:
Do you know that there were two sending units, a 50# and a 80# yours should have the 50# to correspond with the gauge, 1942 and up took the 80# sending unit. This would make the gauge read wrong.
BILL
Click to expand...

Bill, I believe 1942 is still a 50# sending unit. '46 to '53 is an 80# unit.
 
I see them on the flea-pay now and then but the 50# unit it harder to source NOS and expensively priced when you do. 48-9278 would be the 50# P/N to look out for. There is always a possibility that the gauge is a bit off too but the OEM King Seeley stuff is pretty accurate right up until it dies.
 
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OK - thanks for information. I managed to take off the face of my '41 gauge. Just like the temperature gauge, it has two adjustment locations. One for zero set and one for range. I think I can calibrate the sender to match reality. I can send pictures if someone is interested.
 
The originals used a current pulse type of sender, it sounds like the replacement may be some type of resistance unit. Let us know if you can get it to work.
 
JSeery said:
The originals used a current pulse type of sender, it sounds like the replacement may be some type of resistance unit. Let us know if you can get it to work.
Click to expand...

If you measure across a King-Seeley sender you'll get the resistance of the heating element.
 
Ross F-1 said:
If you measure across a King-Seeley sender you'll get the resistance of the heating element.
Click to expand...

If the points are closed. :) Not sure what the starting position is, but if the points are closed you will read the heating coil resistance. If they are open it should be zero. Would be interesting to know what the internals of the replacement units are!

I've never had an oil pressure sender apart, so no idea what the inside is like. The fuel senders have a second calibration coil inside which always give you a resistance reading. Think I have one around, I need to take a look inside and see what is going on.
 
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The King-Seeley sending unit should match the oil pump max pressure. If you have an 80# oil pump and a 50# sending unit, the gauge will read max all of the time as long as you have normal oil pressure.

The points on a King_Seeley unit will always be closed until the heating element opens them, this should not happen when an ohm meter is used to measure resistance

Search swap meets and jeep parts for a good used unit. The last one that I had sold for $75 on epay about 6 years ago.
 
Dads
I'm using an 80# sender an 80# pump with a 50# gauge......the gauge reads somewhat
low but it is consistent from start up to shut off and the needle on the gauge drops
to zero when it should. I've got a bunch of 80#er's for sale.
Charlie ny
 
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NOS 80# units will be marked 80; NOS 50# units will be marked 50, or have no marking at all. Ebay is probably your best bet. See Item No. 272847863449
 
Dads, I have eight of these original sender units, some #50 and some #80. Tested them all with an ohmmeter and got NO continuity between terminal and base on any of them and 3 are NOS in boxes. I did further tests on one NOS #50 which had no ohms reading so I pressured it with 20 PSI air and got a 10 ohms reading. Also I would definitely NOT alter any adjustments inside your gauge as this is set at the factory and should be correct. If you alter it you wont know where you are in the end. You need to sort out a good sender unit to start with. Just have a close look at the winding around the bi-metal contact strip inside the gauge and make sure it is not burnt or overheated. Regards, Kevin.
 
Dads 41, First of all do the test by Ross F-1 in post #3 and establish if the gauge is good by using a "C" or"D" cell. Approx half reading on scale with a GOOD battery. Regards, Kevin.
 
My experience with an 80# sender and original gauge (35-41) ,the gauge reads 1/2 of what it should be and not the other way.
 
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