Temp gauge woes

I did a quick search and didn't get all the answers I need. Here's the skinny.
I purchased a 94 a while back. It has gauges. Temp didn't work. I found that the wire was disconnected from the sender and thought that it was to hide an engine temp problem.
I hooked it up and it worked fine and did not get too hot so I thought I was done.
Since then it quit working again. This time I checked the connection, replaced the sensor twice (I broke the first one in the socket), still nothing.
When the key is off it reads above 0. When I turn the key to start, it reads at max until the key is returned to the run position where the gauge goes dead.
I took the cluster out and noticed a little corrosion? on the solder behind the temp gauge.
I dont know if I can replace the circuit board on my cluster with one from another Jeep, replace the gauge inside or just replace the whole cluster. I don't care about true mileage because this Jeep is going to die with me.
Should I try to run a new wire from the sender to the plug at the cluster?
HELP!
Thanks!
Scott

I'd test it first - you can find a table of resistors you can use (they're like 50 cents each at radio shack, no big deal) from the engine block to the temp sensor wire to test the meter. That should tell you more about whether replacing the cluster will fix it or not - replacing the whole cluster is the way to go, it'll cost about 20 bucks at the junkyard, just make sure you get one from the same year as your XJ (some of them you can use one within a year or two, but it depends. I think you could use a 93 or a 95 but I'm really not sure)

Check from the instrument panel connector to the sensor connector with an ohm meter for continuity.

The temperature sensor should be something like 1365 ohms @ 100 degrees, 93.5 ohms @ 220 degrees, and 55.1 ohms @ 260 degrees; those specs are from the 90 FSM and I know they changed the fuel gauge in later models but I think the temp stayed the same.

Also, if you got real generous and sloppy with thread sealer on the sender it won't read correctly as it grounds through the sensor body to the head.