94 honda accord 2.2, when i start it up in the morning the tempeture gauge will instantly go to overheating, theres no way its allready that hot, and it never overheats. after i drive it for a half hour or so, it will suddently go back to normal and be just below halfway. would the problem be in the tempture sending unit located by the top hose going to the block?

thanks
adam

 

It could be the unit or the wiring. You can download a 94 shop manual from acc 5th gen... thread in diy section. The pdfs at the bottom of the page are chapters from a 94 shop manual.

The sending unit could be bad or the wiring. Go through the resistance and wiring checks on the electrical pdf for the ect sending unit (23-144).

 

The sensor resistance gets lower at high temperatures. So it may be that your sensor has flaky resistance characteristics.

The test for the gauge in the cluster, is to unplug the sensor & short the wire to ground. Have someone watch the gauge because you DONT want to let it peg high (burn out the gauge).

Unplug the sensor & insulate the end of the wire. If it STILL goes up, then you know to look for a short-to-ground somewhere in that wire. Look for insulation rubbed thru & the wire touching something.