question about gauges

[lumpyd]

 I just installed a painless 10110 wiring harness in my 81 cj7 and it seems to work just fine. However, the temp and gas gauges don't work. I have a new sending unit in the tank (3 rd one) and the gas gauge goes on and off. Do I need to replace both of them together?

[calvynandhobbs]

I'm not an electrical person, but I would check grounds first, before throwing more parts at it. I bet 8 out of 10 electrical problems I've ever had stem from a bad ground. Even if it looks good, take it apart and scrape it down. In one of my CJ7s I had to take the entire dash apart and clean every connection due to water leaking through the cowl and windshield through the dash and making a mess of my connections.