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Discussion Starter · #1 ·
So I changed everything on my 1996 2.2 5speed. Hoses, Coolant, radiator, Thermostat, bypass hose and temp sending unit.

50/50 mix of coolant and distilled water.

Hooked up my Actron gauge and started her up, noticed that the gauge went to full H and past actually but the Actron gauge read only 130 degrees. Recheck my bleeding procedures and let the engine run for a bit. Drove it around and the Actron gauge read 203 and the fans came on then went off around 183 ish.

Thermostat is Subaru OEM.

Did this for a while and engine ran fine, Actron gauge showed perfect temp.

Im sure I did something wrong but I cant see what.. I replaced the factory sending unit, tightened it up and reconnected the simple one wire.

What could have happened?:confused:
 

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Not all that familiar with the 2.2, but perhaps we might be able to help narrow it down.

Fans should come on at around 203,, so the Actron readings appear normal.

Does your engine have two temperature sensors (sending units) on the crossover pipe? If two, one is for the temperature gauge and the other is for the ECM, which controls the fans. Is it possible that the connections to them were interchanged?

I believe that both temperature sensors are negative coefficient resistors -- the higher the temperature the lower the resistance. If the temp gauge pegs at H, it means the resistance from the meter to, or through, the sensor is very low. If it's not the sensor itself, it could be a short to ground somewhere in the wire going from the sensor to the gauge in the instrument panel. (If I'm wrong, and the sensors are positive coefficient, then this would suggest an open sensor or a break (rather than a short) in the wire from the sensor.)

Quick test -- if there's a separate sensor for the temperature gauges, what happens at the temperature gauge if you remove the connection at the sensor?
 

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Discussion Starter · #3 ·
I removed the connector to the sensor that I changed and the gauge went down to "C" which is what I expected. Im pretty sure that the engine has two sensors since the Actron reading still works correctly. My only guess is that I got a bad switch. Its Beck Arnley which usually is OEM quality if not OEM itself. Unusual I would say to get a bad one but stranger things have happened.

No chance of switching things around, I only removed that one sensor.
 

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The temperature sensor isn't a switch - it's a variable resistor that changes value with temperature.

But it does seem as if the sensor is bad if the gauge went to C when the connector was removed. If you have a digital multimeter, measure the resistance (Ohms) between the single connector on the sensor and ground (metal case of the sensor) when the engine is cold or the sensor is out. I believe it should be a few hundred Ohms. if it's near zero, then that's the problem.

Why did you change the temperature sending unit in the first place?
 

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Discussion Starter · #5 ·
Well, I must say, I love my Actron gauge.. I decided to put back the original sending unit and everything works perfectly.

I changed the sending unit because originally the engine was running quite warm. It was originally running a bit over the half mark. I changed the radiator, hoses coolant, thermostat because of it running warm. I figured it needed it after 15 years. The hoses were old, the thermostat was a crappy Stant etc... So I wanted everything to be new.
 

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Well, I must say, I love my Actron gauge.. I decided to put back the original sending unit and everything works perfectly.

I changed the sending unit because originally the engine was running quite warm. It was originally running a bit over the half mark. I changed the radiator, hoses coolant, thermostat because of it running warm. I figured it needed it after 15 years. The hoses were old, the thermostat was a crappy Stant etc... So I wanted everything to be new.
I
The temperature sensor isn't a switch - it's a variable resistor that changes value with temperature.

But it does seem as if the sensor is bad if the gauge went to C when the connector was removed. If you have a digital multimeter, measure the resistance (Ohms) between the single connector on the sensor and ground (metal case of the sensor) when the engine is cold or the sensor is out. I believe it should be a few hundred Ohms. if it's near zero, then that's the problem.

Why did you change the temperature sending unit in the first place?
I had this same problem. Car ran hot. Changed the thermostat, radiator and head gasket. Things were fine for a bit then I noticed temperature hand raising gradually then going back down. Changed the temperature sending unit and as soon as I started the vehicle the temperature hand went and stayed above H. Ordered the other temp sending unit that attaches to the gauge to see it that helps. Totally perplexed. 2000 Subaru Outback
 
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