HELP - 92 wrangler jeep - temperature guage malfunctioned

I'm thinking of buying a jeep but the owner said that after she replaced the water pump, the temperature guage malfunctioned. Could anyone tell me how serious this problem could be and how much would it cost to fix. Or is it even worth it.

any information would be great!!

thanks.

Replacing the water pump would not cause the water temperature guage to stop working. I would suspect a broken wire or malfunctioning sending unit. On both the 4 cylinder & 6 cylinder the sending unit is located at the back of the cylinder head. Make sure the thermostat is opening when it should while you're at it.