Temperature sending unit

[97XJSP]

Just wondering, I'm assuming there should be continuity between the terminal and the outer case/ engine block of the sending unit? I have two stock units and neither has continuity... I've finally got my fuel gauge on-line, everything works except for the oil pressure and temp. Oil pressure either sits at 0 or at about 30 and temp stays at zero. Cluster has a good ground and so does the engine block. I'm suspecting sending units in both cases.
Also, when I was trouble shooting the fuel gauge, I checked the resistance between the sending unit wire at the gauge, and ground. I kept getting about 4.4 regardless of the fuel level? Is this the right way to check resistance of the sending unit? Anyway, I put in ten gallons and it read 1/2 tank so I'm happy for now. I did notice that the gauge fluctuates with RPM though, due to changing voltage maybe? It goes up slightly with RPM but seems to settle after a bit.
Thanks!

[Barrman]

The -20 tells you exactly what reading are normal. I don't have mine with me right now so I can't look it up. Are you sure power is getting to the gauges?

[97XJSP]

I went through the -20 manual and and didn't get a whole lot. I did check and the spider harness is good, all guages are getting power. I know the guage/ ground thing has been hashed out many times but most of that seems to pertain to the fuel guage, I didn't didn't find much on the temp stuff. Assuming it's the same circuitry, I think there should be continuity across the sending unit, just like the fuel sending unit. Just thought it was odd that I had two and neither on did...

[Barrman]

Table 2-9 of the -20 says this about the oil psi system:

Stop engine immediately, check oil level. If oil is full, remove instrument cluster and circuit 27 from indicator. Connect a test lamp between bare metal chassis and circuit 27. Turn ignition switch to “On.” If lamp lights, replace lead and perform a similar test on circuit 36. If lamp does not light, indicator is open Replace indicator If lamp lights perform similar test on circuit 36 at sender. If lamp lights, replace sender.

To me that means the sender should have resistance and not be open to ground with no psi applied.

[MJCougler]

When I pulled my fuel tank sending unit, I too could not get an ohm reading. So, I sprayed it down with brake-clean and used an acid swabbing brush to scrub and clean the whole thing. I still could not get an accurate ohm reading. When I put it back in, I used a lot of non-hardening Permatex on the "poor" gasket, new screws, washers, oiled the threads, and it worked.

BTW, where can I purchase fuel-quality "rubber" to make a new sending unit gasket?

Thanks,

[97XJSP]

I'm not sure of other places, but I got my new sending unit from Memphis and it came with a new rubber gasket. I wonder if they might sell just the gasket. My thoughts are that it comes with the unit and they don't carry a sepertate one, but it was a universal unit so maybe it's a common pattern and they do stock a gasket?
Have you looked for any local rubber places? Probably sold by the foot...

[moose3d]

To check the temp gauge and sending unit, unplug it from the sending unit, turn the power on. The gauge should still be on 0 degrees, assuming the wire is good, ground the wire at he sending unit, if the needle on the gauge goes all the way to the right the sending unit is bad. If the needle doesn't move it is the gauge. Remember assuming the wire is good and you have power at the gauge.

To check the oil pressure gage, unplug it from the transmiter, and turn on the power. The needle on the gauge should go all the way to the right, if it doesn't the gauge is bad, assuming the wire is good, ground the wire at the transmiter, the needle should go back to 0 PSI. If it does go to 0 PSI the sending unit is bad. And as I mentioned before make sure the wire is good and you have power at the gauge.

Another thing to check is to make sure that the connection is tight on the sending unit and gauges. I know from Motor Pool experience that after time the little clips come off the connections and don't give you a tight connection.

Hope this helps. Any questions let me know.

[97XJSP]

That will be very useful advice. I had figured most of it out, but wasn't sure what each guage should read when "grounded"
Thanks!