[2.5x_sleeper]

@Derek'sForester I see this is your first forum post, so welcome to the forum from Oregon! :

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

I keep trying to post questions here, but only one has ever showed up. <snipped>

No need to create a new thread when you already have an active thread on the same subject. Per the forum posting rules, your threads have been merged.

Again...

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Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

@Derek'sForester did you read this on my previous posts?

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Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

No, no issues. I'm just trying to help you get the help you're looking for.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

@Derek'sForester if connecting the test connector verifies the main & sub fan are working, then that appears to be pointing to a ECM or sensor issue. Note that the fans are controlled by the ECM & not directly by the test connector or sensors.

Also...
Is this fan issue a new problem that just started up?

Bobby...

'99-'02 Forester

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

If it's the ECM then I guess the car is toast at 215,000 miles.

Not saying the ECM is bad, but they can be found used at a reasonable price. Just make sure the vehicle it came out of matches your Forester, especially MT or AT.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

Did I read that you replaced the engine coolant temperature sensor?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

The earlier ECM are pretty basic... no serious magic. As long as the ECM is off a like Forester, you should be good.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

@Derek'sForester questions:

[1] Just to verify... when you connected the green test connector, did the both radiator cooling fans operate?
[2] Have you read the coolant temperature with a scan tool, Scangauge II or an UltraGauge?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

I just wanted to be 100% sure.

Curious that the radiator fans don't operate when the A/C is activated?

The wiring diagram shows the radiator fan relays are controlled by the ECM, which applies a ground (-12V) to the relays to operate one or both.

The coolant temperature sensor & A/C system connect to the ECM, which controls the radiator fan relays. Neither directly connect radiator fan relays.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

Yes. I replaced it last Sunday. It was the one in the back of the engine under the intake manifold. It had a three prong connector. It didn't seem to make any difference. <snipped>

You said the coolant temperature sensor had "3 prongs". Did that sensor have 3 wires or 2 wires?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

It's really hard to see, but as far as I can tell there are two, a green one and a white one. I'd have to disassemble the ducts leading to the throttle body again to get a better look.

The wiring diagram shows a 2 wire coolant temperature sensor, so your "3 prong" description threw me.

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

This is a VERY curious problem!

The radiator fans operate when the test connector is connected, so that proves the radiator fans can be controlled by the ECM... pins [a3] main fan [a12] sub fan.

The coolant temperature sensor connects to the ECM, pins [c14] - Does the ECM see this sensor... the coolant temperature? This needs to be verified with device attached to the OBD2 connector.

The A/C system connects to the ECM, pins [b27] [a17] [c30] - Does the A/C work... was it working?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

Curious... if the coolant temperature is 160F, then that's too cool for the radiator fans to operate. In addition, at 160F how can the coolant gauge be showing hot, in the red?

Normal coolant temp is 190F to a touch over 200F.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

I replaced the temperature sensor, not a fun job <snipped>

@Derek'sForester questions:

[1] Did the coolant gauge work correctly before you replaced the sensor?
[2] Was that replacement sensor new or used?

The Subaru technical service document calls this sensor "Engine coolant temperature sensor and thermometer" & says it's 3 pole. The wining diagram shows a 2 wire sensor! Assuming the wiring diagram is correct, then the ECM would also have the same sensor data as the coolant gauge.... HOT & should be activating the radiator fans.

► Disclaimer - the earlier Subaru technical service documents for the SF, '98-'02 are VERY difficult to navigate & I have found errors!

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

If you're replacing the coolant thermostat, most forum members would recommend going with a factory/OEM part.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

@Derek'sForesterI have this nagging feeling your issue is electrical... specifically, grounding. Just my guess of course.

The grounding in the earlier Forester is known to be deficient. If you haven't already, I'd recommend verifying all the engine compartment grounds be checked for corrosion & tightness. Subaru uses a lot of "star" washers to cut thru the painted surface to the metal. That's a quick way to make a ground connection, but not the best way. I like to disassemble the ground connection, scrape off the paint where the connection will be made. Then I coat the everything with NO-OX-ID A... you can also use dielectric grease, but I prefer the heavier grease. Once everything is reassembled, you'll have a solid ground!

As to the engine coolant maintenance, take a look at this post that I had bookmarked.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

So I changed the thermostat today. Still no luck.

I'm assuming the radiator fans are still not operating.

Questions:

[1] What is the coolant temperature?
[2] Is the coolant gauge still going into the red?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

How are you getting that 160°F coolant temperature reading?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

[2.5x_sleeper]

The A/C doesn't work. My son said it did in the past. We haven't needed it for months, until this week.

This could explain why the radiator fans don't work when the A/C is turned on.

The coolant gauge appeared to work correctly before it was replaced. The replacement was new and came from Napa.

If the coolant gauge worked before the coolant temperature sensor was replaced, then that may be pointing to an incompatible aftermarket part.

From my scanner on live mode. It goes up to 160 degrees and no higher before the dash gauge gets almost to the red. I don't let it get to the red.

If that 160°F coolant temperature reading is accurate, that's too low for the ECM to call for coolant cooling... to turn on the radiator cooling fan(s).

► Disclaimer - I'm not a mechanic, my career field was in electronics... I do this stuff for fun, so verify any information I provide before investing any money on parts.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]