oil and temp gauges read high

1991 XJ ... Oil pressure and coolant temperature gauges have both been high for a while. I replaced the senders first, gauges didn't change. I verified the oil pressure sender was accurate--the FSM says ~1 ohm per PSI, the sender shows ~20 ohms at idle (about ~20 PSI), but the gauge shows 60 PSI.

Coolant temperature gauge is also high, instead of showing ~200F at normal operating temperature it shows ~230F. I can't find a reliable test for the gauge sender.

I recently replaced the head for other reasons, and I cleaned all the ground points that I could find while it was off.

I'm wondering if the gauge ground is dirty and adding resistance? I was under the impression that would affect all the gauges though? Maybe the bulkhead connector is dirty?

Any other ideas?

try checking the resistance from the connector going to the cluster.
its showing A1 is temp gauge and B7 is oil pressure.

OIL PRESSURE GAUGE RESISTANCE TABLE
Oil Pressure (psi) Ohms
0 ...................................................... 1
40 .................................................... 46
80 .................................................... 87

FUEL GAUGE RESISTANCE TABLE
Application Ohms
Empty ................................................ 105
1/2 Full .............................................. 33
Full ................................................... 5

TEMPERATURE GAUGE RESISTANCE TABLE
Application & Test Temperature Ohms
100F (38C) ...................................... 1365.0
220F (104C) ....................................... 93.5
260F (127C) ....................................... 55.1

Good idea. That the connector on the back of the cluster?

ps--I cleaned the bulkhead connector and values dropped about 10%, a little bit but still way high.

yes check the wires feeding into the cluster. that will let you know if its the cluster thats got an issue or the wiring. my guess is some dirty connections. and that you cleaned some and it got better.

Wire screws on the cluster were a little loose, cleaned and tightened, no difference. Ground wire from the gauge connector has ~15 Ohms resistance to the battery via jumper cable with 0 Ohms. I moved the dash ground to the fender stud and it helped a little but still about ~7 Ohms between cluster connector and the stud. Obv there is some resistance in the dashboard wiring. Heater core sprung a leak a couple of months ago, so I plan to R&R the whole dash in the fall anyway. At least I know where the problem is now. Thanks for the suggestion.