1989 honda civic std hatchback with a d15b1engine, 4 speed manual transmission.

Got a over heating issue at idle and at a stop lights, temp drops to half level when i accelerate a constant speed and does not over heat on the highway. When i turn on my ac and press the ac button on console both fans turn on the driver and passenger side, but does not turn on with ac off, idle or at stops. So fans are not the issue ???Doesnt leak coolant on driveway and no steam is xoming out of under the hood when it indicated its overheating levels, does not over fill my resivor tank. I check the coolant level in radiator and its full. 50/50 antifreeze mix. Checked top and button radiator hose by squeezing and it felt hot and under pressure. Also everytime i turn on my left turn signal the coolant temp gauge rises and acts like a blinker up and down at the top of gauge. Any ideas as to what is causing this.