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Plug in the green diagnostic connectors under the steering column.

 

The fans should cycle in time with the fuel pump, and check engine light.

 

This is Test mode, and will output any present/current trouble codes too.

 

But it's also handy for testing fans and fuel pump operation.

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There may be an air pocket in the heater core. Add coolant to the upper radiator hose. BE aware of any leaks (water pump) or coolant pushing out of the overflow. Sounds like low enough coolant for the heat to get weak, but not enough to overheat. This would explain the fans not coming on if there is an air pocket around the CTS. The CTS controls the fan, and the gauge is a separate sensor like an ea82

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It's possible that your heater core is partially plugged as well. If it was warmer out, I'd suggest connecting a garden hose to your heater core to flush it.

As mentioned above, an air pocket in your cooling system can cause a lot of problems. I've learned to disconnect one end of one of the heater hoses and turn it up so it's almost as high as the radiator neck. Then slowly pour in coolant so the air can escape form the heater hose. Once coolant starts to come out of the heater hose, or heater core end, stop and hook it all back up. Sometimes there will still be air in it, and you'll know when the temp climbs above normal when you first start and idle the engine. If it does climb, just shut it down and walk away until it cools off, once it does and the rad cap is removed that air usually escapes. Sometimes squeezing the rad hoses, with the rad cap on and system closed, to "pump" the coolant around will move the air so it can find it's way to the rad cap.

 

Is it possible that the rad itself isn't getting hot enough with the cold temps outside? Where's the fan switch on that year Legacy? If the engine is hot and the rad is not, you may have a clogged radiator or bad water pump. The impeller can rust away if the coolant system hasn't been maintained over the years. Installing an aftermarket temp gauge to see exactly what the temp is may be the way to go too.

Edited by Frank B
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Dunno if the 91' is much different than a 95', but if it has AC (even if the belt is removed or AC compressor is omitted) turning the AC on in-car should kick the fans on for quick reference. Also, (at least on my 95') turning on front windshield defrost (selecting the defrost button ONLY) will also kick the fans on, but I'm assuming this is only on AC equipped cars. Makes for super quick fan ON tests and emergency "fan ON" scenarios, which is nice.

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Mine sits at the halfway mark too. This car also heats up incredibly fast too. It's been around mid teens to low 20's. Start it up, idle for about a minute, drive off (I keep RPM's low until it's more warmed up so just baby it for a couple miles) and within 1.5-2 miles it's nearly at the halfway mark and blowing nice, warm air. So glad I bought mine as a winter vehicle instead of a Ford Ranger 4x4.

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