1984 toyota 4x4 sr5 22r.... awhile back i noticed my water temp gauge on the dash acting strangely (needle dropping to zero suddenly, then picking back up, or just barely reading anything...) i replaced the water temp sending unit, and everything seemed to go back to normal. a couple weeks later the gauge stopped reading again.
now my oil pressure gauge is reading nothing. the motor is full of oil and the truck still seems to run normally. what the hell is going on? are these signs of the gauge cluster crapping out? both of those gauges are on the left side of the cluster one on top of the other... how long would the truck run with no oil pressure? i just saw a sr5 cluster at the junk yard last week... i could go and get it, unless i am better off fixing the one i have...
im getting ready to replace this motor anyway due to very low compression in cyl 1...

 

well, i figured out my oil pressure gauge. it seems to work better if i have it plugged in to the sending unit... what about the water temp gauge. i have a new sending unit and the wire coming into it has a little more than 10V on the multimeter.. any ideas would be great!

 

had a similar problem with the temp gauge. the temp gauge would read normal then bounce to zero and go back to normal. found my problem was with the gauge. fixed it by changing out the gauge.

 

If you changed the sending unit and it helped for a while, I would think the connector on the wire is getting corroded or is loose. Try either cleaning it really well or just put a new connector on the wire.