I am having an issue I did my summerize two weeks ago everything was fine yesterday installed hyd steering. I started the engine and to bleed the rest of air out and now I am getting the red light and needle is at zero. I swapped oil sending units and the gauge reads 10 psi and then nothing. I put a mechanical gauge on it and has 60 psi idleing warmed up. I was wondering anyone have this issue or ideas of what it could be.

Also I tested the sending wire by grounding it out the gauge moves to about 20 psi and thats it.

I am lost on this one
Thanks

thread sealer on adapter and sending unit can cause weird readings

Get to the back of the gage and ground the sender wire.

If the gage now goes full scale:
Check the connections at the back of the gage, and any terminal blocks between the gage and the sender.

If it does not go full scale - bad gage.

Thanks for the replys I figured it out loose wires at gauge

you pretty much sumed it up,,i would have to say that the gauge took a crap..advise,when testing gauges use a 1 wire test light as a isolater for the sender for the gauge,,grounding the S lead on the back of the gauge can distroy it..gaffrig gauge?? they have their own sender's,using another type may cause false readings..

I keep several resistors in the range of 20-80 ohms. Or you could use a variable resistor/pot. Glad you figured it out