temp gauge and speedo has a mind of its own!!! need help

[zozo87]

need some help as i am now at wits end with my car, while driving the temp gauge decides it wants to go straight up to hot with the hot warning coming up on my dash, then once you pull over to check it out the gauge goes back down to normal temp, the motors not even hot the water and coolant level is good but it randomly decides its hot, and while coasting around right hand bends the speedo drops down to 0 then finds is way back up to the speed your doing after you straightern the car up, any ideas? one last question when i start the car i have a "serv error" displaying on the dash for about 10 seconds. i love my car but its been nothing but drama from day dot so any help would be much appeciated
thanks zo

[jasonzzz_petey]

Try checking the earth wire at the back of your alternator make sure its making gd connection
Mine was fked and made the speedo cut out and temp drop to 0

[red_spider]

check your terminals.i had a similar problem and it was the stinger terminals i put on when i did my stereo i took them off and problem solved