I had a very long post going before but I have decided to start over and summarize it. HELP ME

The Car: I have a 97 Legacy 2.5 180K miles that is overheating when I bought it. It did have a check engine light for a speed sensor

The Problem: The radiator fans will not come on. They will not turn on when the engine is at temp and it will not turn on when the AC is turned on

How to force them on: I do one at a time

 

1) Disconnect the middle bulk head harness. This throws 3 codes a) P0117Coolant Temp Sensor P0122 TPS c) P0325 knock sensor

2) Disconnect the Coolant Temp Sensor

3) Connect the green diagnostic connecters under the dash driver side

4) Ground out the fan at the ECU

What I have replaced

 

1) Coolant Temp Sensor

2) ECU

3) Every Relay in the engine compartment fuse box

4) Speed sensor

5) I checked every fuse in the car

What I am convinced of:

1) I have a Short in the engine wire harness

2) Something is wrong with AC system

Notes:

I have 8 volts at the wire that connect the engine coolant temp sensor when I disconnect it from the coolant temp sensor

Can you plug in a reader to check what temperature the ECU sees the water being?

First let me say that since you already have a lengthy thread going on for this problem you shouldn't start another one for the same thing. This leads to needless running around on things already covered though you did state a lot of the things we previously covered. You could have just summarized in the last thread.

 

In the previous thread I wanted you to measure the voltage of the 2-wire coolant temp sensor for the ECU. It looks like you got 8 volts across the wires. I'm not sure what the voltage should be but that may be low and if so that means there is a problem on those wires somewhere. I would think there should have been a code set if that was the case so maybe this is really okay. Manarius's idea of looking at the coolent temp through the ECU is a good one and would verify the circuit if the display shows normal temps.

Ok, how do I verify it at the ECU, all I have is a OBDII reader and a multi-meter from radio shack.

If you can somehow get your hands on a scangauge, it will tell you what the ECU is reading as the engine coolant temp.

OK OK, Fixed. I installed a Used OEM Coolant Temp Sensor and now the fan roars on when its at temp. Turning on the AC does not engage the fan nor does the clutch come on. I am calling this a seperate issue. I hate lending my tools out because I do not have my ac test guages. Thanks to all that have helped me.

Good deal. One down and one to go. The AC fan is still going to need some investigation. You're welcome for the help. Thanks for the feedback.

[...]Turning on the AC does not engage the fan nor does the clutch come on.[...]

Might be due to insufficient refrigerant charge. See this thread for a way to check for that without gauges: http://www.ultimatesubaru.org/forum/showthread.php?t=59414

I tested with the gauges. There is 0 charge in the system. And that explains why the clutch will not come on

I had a slow leak on my 98 Impreza OBS. I replaced all the orings, but the only ones that looked bad were the two on the compressor. It fixed the problem. The compressor orings had taken a set and were flat on one side.

 

PS take the orings with you to match them. Even the Subaru Dealer could not pull up the correct part number and wanted to order the parts shown as none were in stock.

I tested with the gauges. There is 0 charge in the system. And that explains why the clutch will not come on

 

Well you are closing in on the trouble.

I tested with the gauges. There is 0 charge in the system. And that explains why the clutch will not come on

There's also no reason for the radiator secondary cooling fan to come on when the A/C switch is "turned on" if the compressor can't run.

What you have all helped me with to date

1) Replaced Bad AC/Heater resistor. Now all speeds work for the interior fan

2) Busted Coolant Temp Sensor. THIS MUST BE REPLACED OEM

3) AC Clutch not turning on, I will do a leak test this weekend.

 

What would all of this have cost at the dealer?

It's hard to say for sure but I would think a good savy tech could pin down the troubles within a couple of hours. Fixing the troubles may take longer.