Oil pressure sender values

[curtis73]

What resistance values should I expect from my oil pressure sender? I'm getting about 200 ohms at rest and it reduces from there as I squirt some air pressure in it.

[DelawareDave]

According to Beede gauge co, 240-33 ohms.

[roostwear]

That's standard for newer aftermarket o/p gauges. Napa has them, or just use one for a SW (single gauge) and you're good to go.

[curtis73]

What's an SW?
The gauges are VDOs from about 1982-83. I have four senders that I've tried and I'll just spit out what I know and maybe you can help me diagnose.
I wired everything up and when I turn the switch on the oil pressure gauge pegs at the top. I took off the sender and tested it (analog tester and it only has a 1k setting so its frustrating) but it appeared to offer the right stuff; 200 or so down to 50-ish. But when I touch the sender wire to it, it pegs as if its getting too little resistance. So, I suspected the gauge was bad but I don't have any other gauges to test.
I now have 4 senders; two nipple style and two can style. One of the nipples is in use at the back of the intake and it has continuity above 5 psi. I'm using it to activate the relay for my fuel pump. The other nipple style I think is a broken reverse switch. It provides about 5000k with no pressure and opens the circuit with pressure. The one can style I have seems to give the right resistance values but pegs the gauge. I just bought a different can style that was listed as being for a 60 psi gauge and specifically said NOT for the dummy light. When I give it pressure it just closes the circuit. No variable values, just open or closed.
FRUSTRATED!!!

[roostwear]

SW stands for Stewart Warner. Here are the part #'s for senders with 240-33.5 ohm range.
SW
80psi= 279A
100psi= 279B-F
Datcon
80psi= 02504-00
100psi= 02505-00
Napa as them and may be able to cross the Datcon #'s

[curtis73]

Excellent, thanks for the part numbers.
It looks as though the gauge may be bad. I called VDO and the tech told me to find something that offers a resistance value of about 100 ohms and try it. He said that should register about half of the guage's travel. The only thing I could find was a microphone that offered 600 ohms and it pegged the gauge as well. So, I would think that if 600 ohms pegs it, it must be wasted if its designed to operate between 200 and 50.
Is my reasoning right?

[roostwear]

Dig up a potentiometer and grab your VOM. Easy enough to do and you know for sure.

[curtis73]

I guess I could buy a light dimmer or take one out of the wall in the house.

[DelawareDave]

Go to Radio Crack and buy a 1/4 watt, 100 ohm resistor. Should cost about 2 or 3 bucks, and there is probably 3-5 of them in the package.

[curtis73]

Ok, a 600 ohm microphone, a 200 ohm sender, and a 100ohm-1/4watt resistor all pegged the meter, and it required tapping the gauge to get it to release the needle.
Does that mean a bad gauge?

[roostwear]

If the resistor pegged it, it's bad. The needle sticking ( I assume it's with power removed) seals it.

[curtis73]

Ok, thanks for all the help. Now I have to decide if I can put up with one gauge that's different from the rest or if I have to be vain and get a whole set :)

[roostwear]

What do you have in it now?

[curtis73]

It has VDO gauges, unknown flavor. They're very 80s looking and black with white and blue markings. I picked up a cheapy Teleflex that is the same color scheme to poke in there for now. It takes the same sender and its also 0-80.