1983 944 engine swap / 1985 engine

[hindswillrox]

:help: Hi, I have just completed an engine swap in my son's 1983 944, we found a 50,000 mile engine out of a 1985 944. The engine runs great but the temp gauge reads that the engine is running hot. There is a difference in the senders for the coolant gauge, the unit in the 85 engine is an internal probe as it threads through the block and in to the coolant galley and is (wet). The sender in the 83 engine is a dead plug in to the block, dose not go through the the block in to the coolant galley and it is not (wet). I believe the sender in the 85 engine sends a different signal do to it's nature and is sending a false signal to the gauge.

So this is how I have diagnosed this problem in order to come to this conclusion. First of the cooling fan dose not come on until the temp gauge is almost in the (red) and will shut off with the gauge just below the (red) zone on the gauge. the engine has never been hot enough to pop the over flow (The coolant tank has a new cap and the fan sender switch is almost new and worked correctly with the old engine in the car) This has been frustrating as no one seems to have an answer for this. So the next thing we did is to make a fitting to connect a hose to the bleed screw hole and allow coolant to drain into a catch bottle with my wife's meat thermometer (much to her dismay) in the catch bottle, we ran the engine through the heat cycle with the fan turning on at 190 and shutting off at about 180. This tells me the sender is sending the wrong signal to the gauge. Any help on how I can tell if this is the case and how to fix the issue would be appreciated, ( I have talked to the tech at my local dealer and he had no idea how to fix this or if my assumptions are correct)

[magcuda]

sounds about right. what does the temp gauge read when the engine is "cold"?

you can put a resistor(s) in the wire to the sensor untill you get it reading correctly on the gauge.