Gauges - When they Work they Work... till they don't???

[J and L Nast]

I have 2 Nissan Pulsars (1987 & 1988) NX's both had issues with Fuel Sending units

 

Now I've got new Fuel Sending Units and all Gauges worked.. then they stopped working, then they started working again????

No idea?  By All I mean Temp Gauges, Fuel Level, etc. 

 

Any ideas on where to start Trounbleshooting?

I've checked fuse's sending units and temp sending unit. 

 

The odd part is is works, then next time I start it doesn't?    

[Trevor]

Sounds like loose connections but where is another question all together