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Funky wiring and temp sensor



I need some help in determining what a blue and black wire hooked up to, what seems like a temp sensor, on the right head (right side if you were sitting in the car). The engine has been rebuilt and has a new pump, cleaned out radiator, new hoses, thermostat, timing is good. The point is everything is practicaly new but it is still reading hot. I just got the car from getting a true dual exhaust put on it. As I was driving it back from the shop, with no hood mind you, to the mechanic (so he could finish putting some new bushings in the rear suspension) the temp gauge was indicating it was at 220. Someone (rpound i believe) was enquiring about this and found that the gauge was reading 10 deg above what it actually was. I took the main street route, there was a lot of stop signs, lights and school zones. I figured it shouldn't overheat due to the fact that the hood was off and air should flow with ease through the radiator. The gauge was still climbing when i reached the mechanic.

My questions are

Is the gauge electrically run, or is does the heat from the wire have to travel to the gauge?

I need to know so i can either insulate the wire or get the gauge checked. The mechanic stated that if the engine overheated that the engine would be hard to crank. when i stopped with the mechanic i cranked it 3 times with out much hesitation.

does this blue and black wire have to do anything with the temp sensor.

Any HELP would be greatly appreciated!

p.s. Its a 79 L-82 thanx
The temperature sending unit is in the head, between number 1 and 3 cylinders (left side of car). It should be screwed directly into a water jacket. You can remove the sending unit and test it with a VOM, meat or candy thermometer and a pan of water on the stove.

The sending unit if accurate, should read the following:

75 degrees = 569 ohms
100 = 410
160 = 150
180 = 123
200 = 94
210 = 83.5

I did not include all of the readings from 75 - 210. However, you can see that the scale is not linear and the extropolation indicates that the sending unit is normally most accurate between 160-200+ degrees, therefore I have included more of the readings in that range.

In dealing with my heating problem, I have discovered the following:

If it heats when idleing or moving through traffic around town but does not heat at speed, then I would suspect the fan clutch.

If the opposite is true, it heats at speed, but remains cool around town, suspect these things and ask these questions: is the 'chin' spoiler in place? Are all of the radiator seals, including the radiator to hood seal in place? (It can not be stated emphatically enough how important these seals are in a C-3). Is the timing retarded? What is the coolant mix and the true condition of the radiator?

Over time the metal in the radiator begins to lose it's ability to transfer heat, because of scale and corrosion. This is known as 'heat rejection capacity'. If you can determine that airflow is not a problem, this could very well contribute to your situation. Even a visual inspection is not always the greatest indication of the condition of the interior of the radiator.

My .02

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