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Old 05-28-2020, 10:01 PM   #1
J3ss1987
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Dazed 2000 saturn sw2 cooling fan issues

My 2000 sw2 saturn wagon's cooling fan stopped working a few months ago. I changed the temp sensor and temp sensor connector. It didn't work. Though when I unplug the temp sensor connector the fan will turn on. I couldn't figure out so I just ran my A/C to keep the fan on. The other day it got hot so I checked it and now the A/C won't keep it on any more. I unplugged the temp sensor again and the fan will run. I checked the fuse under the hood and the relay under the hood they are fine. Any suggestions are extremely appreciated!!!! Thx
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Old 05-29-2020, 12:45 AM   #2
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Default Re: 2000 saturn sw2 cooling fan issues

If you have access to a scanner, monitor coolant temperature and see if the fan kicks on at around 221F.
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Old 05-29-2020, 11:35 AM   #3
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Default Re: 2000 saturn sw2 cooling fan issues

Also use that live-data from the scanner to see if the fan is being commanded on by the PCM. Same for A/C, see if it is being shown in live-data as "on" even when the fan won't run. Report any codes set; you should get something just by disconnecting the ECT sensor.

Yours is a puzzling issue, as all the wiring (including relay/fuse/connectors) seems to be OK since the fan will come on when the ECT is disconnected. However, running the A/C should also signal the PCM to turn the fan on. We need to be certain these "conflicting" symptoms are being reported accurately, as the only possibility I see to account for them is a bad PCM.

Oh, and I gotta ask... the A/C does run (cool) properly even though the fan is not coming on?
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Old 05-29-2020, 03:34 PM   #4
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Default Re: 2000 saturn sw2 cooling fan issues

deleted - reread the OP
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Old 05-29-2020, 03:51 PM   #5
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Thumbs Up Re: 2000 saturn sw2 cooling fan issues

The A/C runs perfect besides when the car gets hot As soon as the temp gets hot I'd say 3/4ths the ac runs warm, but that's what all cars do when they get hot. Where is the pcm ? I don't have anything to read the computer. No codes besides the low water light has been on since the beginning of this problem, I think there maybe a small leak somewhere at the bottom of the water reservoir. When I unplugged the temp sensor connector the computer sent a signal. I'll check to see if the temp sensor has the 4 bumps (what is the reason for them? ). Thank you for your help
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Old 05-29-2020, 05:27 PM   #6
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Default Re: 2000 saturn sw2 cooling fan issues

Does anyone have a diagram of the cooling system how many sensors there are, Is there only the coolant temp sensor? I know my Ford focus had 2 and they burnt up so I just put a switch in. Im trying to keep everything original and not rig it up. It has 56000 mi. Should I change the temp sensor again maybe it was junk to begin with ?
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Old 05-29-2020, 07:04 PM   #7
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Default Re: 2000 saturn sw2 cooling fan issues

There is only one coolant temp sensor on that. If you are going to try maintaining this (or any other modern) car, then investing in the means to get live-data is essential. That can be very cheap hardware-wise (ELM327), and free software-wise, but there is some investment in time to learn how to use the SW.

However, the temp sensor is very cheap ($10) and easy to change, so if you are going to "throw parts at it", then that is a good choice to start with.

Understand, without live-data (or equivalent testing with a meter) you could replace every sensor on the engine, and the PCM, and still not find the problem if the problem is in the wiring.
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Old 05-29-2020, 07:24 PM   #8
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Default Re: 2000 saturn sw2 cooling fan issues

Getting live data would only work if it's throwing a code right??? Or wrong??? I've already changed the temp sensor once and the temp sensor connector. So why does the fan not turn on but the temp gauge reads correctly if that was the problem? Could I have attached the connector wrong?
Thank you for your time!!!!!!
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Old 05-29-2020, 08:05 PM   #9
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Default Re: 2000 saturn sw2 cooling fan issues

Quote:
Originally Posted by J3ss1987 View Post
The A/C runs perfect besides when the car gets hot As soon as the temp gets hot I'd say 3/4ths the ac runs warm, but that's what all cars do when they get hot....
AC runs cold as long as everything runs correctly in every car, truck suv, reefer, bus, train, etc.

As suggested, buy a wifi ELM 327 adapter for cellphone use and free app to display generic OBD II codes and sensor data. A few dollars more and extensive data may be retrieved for more info. Wifi OBD II adapters coupled with Torque app (most members here recommend it) for around $30.

A reader should display coolant temps. S-series cars runs between 185F-200F. A reader retrieves data from the body control module connected to the pcm, airbag and abs modules. The bcm is the gateway between modules and reader. With a cold engine, the coolant temperature should display ambient temperatures and as engine coolant warms up, display rising temps. The reader pulls data as the engine computer sees it.

If your ac stops cooling when outside temps gets hot, there may be something wrong with the cooling fan, fan circuit or the ac system. Ac running requires fan operation - the condenser coils get hot so fan running blows air continually thru condenser coils and hot radiator. If the fan doesn't run when ac is turned on, the coolant temps will rise to overheating conditions. This may be what you're seeing. Every S-series car with ac running usually displays coolant temps dropping as the fan forces airflow thru condenser coils and radiator.

With engine idling, turn on ac and visually check for fan operation. It's supposed to be running.
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Old 05-29-2020, 09:15 PM   #10
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Default Re: 2000 saturn sw2 cooling fan issues

My 98 SL2 has the same issue. Car will overheat if left sitting and idling, unless the AC is on which engages the fan, then all is well.

Only discovered the issue after changing the radiator and running it for a bit with the coolant tank cap off to make sure the system was full of coolant. It overheated in the driveway and the fans never kicked on... Now every once in a while if I'm cruising through town with the sunroof and windows open and no AC on, if I happen to get stuck in traffic or take the car through a drive thru, I can watch the temp gauge slowly creep up. It's only noticeable if I'm sitting for 5-10 minutes, and I've learned to just keep an eye on it and just kick the AC on when I notice it start to creep, so it hasn't fully overheated on me on the road, but it still leaves me with an uneasy feeling...
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Old 05-29-2020, 09:41 PM   #11
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Default Re: 2000 saturn sw2 cooling fan issues

tJ3ss1987, when you replaced the ECTS connector, how did you attach the wires? The only approved way is to solder and cover with shrink wrap. Never wire nuts, never crimp connectors and these 2 methods will fail.
Have you verified the voltage across the 2 ECTS connector pins? Should be -5vdc if I recall correctly (IIRC).
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Old 05-29-2020, 10:01 PM   #12
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Default Re: 2000 saturn sw2 cooling fan issues

Got it? Live-data is valuable even if no codes are set. That ECT sensor, specifically, can fail "in range" and not set a code but cause the engine to start/run poorly. Same for TPS, same for MAP sensor, same for... well, you get the idea, I hope!

Please confirm: does the fan still consistently come on when the ECT sensor is disconnected? Does the fan never come on now when the ECT is connected and the A/C is selected?
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Old 05-29-2020, 10:06 PM   #13
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Default Re: 2000 saturn sw2 cooling fan issues

So was just looking under the hood and checking wires. The wires near the fan motor there are a few I believe the oxygen sensor, the power for fan and one other not sure what, but when I wiggled it the fan turns on ( A/C was off, and temp sensor connected, and the temp gauge was a 1/4 of the way up). Thanks I'll have to buy one of those and check it out! I'm not sure where or which wire is causing the problem but I'll be jacking it up tomorrow
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Old 06-18-2020, 02:16 PM   #14
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Wrench Re: 2000 saturn sw2 cooling fan issues

Replaced the fan assembly and fan assembly connector. The fan is only running while A/C is on. QUESTION.... What does the temp sensor do?? I already changed the temp sensor and the temp sensor connector but I want to know what it does so if I unplug it the temp gauge doesn't work so i plug it back in and it does ... does that mean it's doing everything it's supposed to??? I'm trying to figure out what other component would turn on the fan ... is there anything other than the computer, and why would the computer just not work for the fan?? Hmmmmm I don't want to kill my ac Condenser using it so the fan will run. Thank you for your time!!!!
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Old 06-18-2020, 02:20 PM   #15
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Default Re: 2000 saturn sw2 cooling fan issues

Does anyone know where the computer that controls the fan is? I believe it's under the dash if so I'm soooo not interested in taking the dash apart.
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Old 06-18-2020, 02:39 PM   #16
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Default Re: 2000 saturn sw2 cooling fan issues

The fan is controlled by the PCM. On your year (gen3) I think the PCM is in the engine compartment, in front of the battery.

If there is any combination of A/C on, ECT sensor unplugged, etc. that will reliably/repeatedly result in the fan operating, then the fan/relay/wiring/PCM must all be OK. The way to confirm is using the live-data. See if the fan comes on every time live-data shows that it is commanded on.

I have to admit, though, that I am still confused as to whether there is a combo that will reliably turn on the fan. Please confirm or clarify.
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Old 06-18-2020, 03:29 PM   #17
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Default Re: 2000 saturn sw2 cooling fan issues

Everything is plugged in correctly, the fan will only come on if ac is on. I've let it sit till it got hot to check if it would come on and it did not. The dash temp gauge works fine.
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Old 06-18-2020, 04:09 PM   #18
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Default Re: 2000 saturn sw2 cooling fan issues

My understanding is that the (engine cooling) fan will also come on if the ECT is disconnected and the A/C if off. Is that correct?

If I am understanding correctly, then the problem is almost certainly in the ECT circuit. You need that live-data, or you will may wander in parts-swapping circles for a long time. If you refuse to use live-data, then my next suggestion is to read the ECT signal voltage right at the PCM connector; back-probing the harness with everything connected electrically and using the ice/boiling baths for immersing the ECT sensor into.
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Old 06-18-2020, 05:23 PM   #19
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Default Re: 2000 saturn sw2 cooling fan issues

Quote:
Originally Posted by J3ss1987 View Post
My 2000 sw2 saturn wagon's cooling fan stopped working .... I changed the temp sensor and temp sensor connector. It didn't work. Though when I unplug the temp sensor connector the fan will turn on. I couldn't figure out so I just ran my A/C to keep the fan on....
The cooling fan circuit is in two parts. The cooling fan relay (closed contacts 30 and 87) and fuse is the power side. The pcm controls the electronic side of the fan thru relay contacts 85 and 86. The ac and cooling system share the same fan circuit. When ac is working (not dead) the fan is running. When coolant temps exceed (approximately) 220F, the fan runs. Using ac and seeing/hearing the fan running verifies the fan circuit is fine.

Unless you can buy a reader or ask Autozone if their reader displays coolant temperatures, you're guessing on how hot the engine is. Your temperature gauge isn't near the redline and fan turn on (by gauge) would be between 3/4 and full needle deflection on the temperature gauge. Error codes or lack of any is separate from live displays of data; O2 sensor, map, intake air temperature, coolant temperature, etc. Good/better readers have live displays to monitor varying signals as they occur in real time.

Quote:
QUESTION.... What does the temp sensor do?
The engine coolant sensor sends temperature signals to the pcm. Pcm programs determines when to turn on the cooling fan; when ac is working (not dead) and/or when coolant exceeds 220F. When you disconnected the sensor and saw the temperature gauge go dead, the pcm lost coolant sensor signals so zero temperature needle movement occurs. The pcm detects this as a fault and automatically turns on the cooling fan because its safer to run the fan whether or not the engine is overheating to prevent any chance of overheating.

Many members feel their engine runs hot as gauge needle varies from 1st/2nd/3rd generation S-series. Fan turn on still occurs around 220F no matter where the needle is.

When you replaced the fan, did you check for airflow direction? Pusher fans means the fan is placed in front of the ac condenser coil/radiator to force airflow thru condenser coil and radiator. Puller fans means its placed behind the radiator, pulling airflow thru condenser coil and radiator.
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Old 06-18-2020, 05:25 PM   #20
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Default Re: 2000 saturn sw2 cooling fan issues

Yes if the ect temp sensor connector is unplugged the fan will run. I've already bought and replaced the ect temp sensor & temp sensor connector. When unplugged the dash temp gauge doesn't work, so I figure the new one isn't faulty since the dash temp gauge is correct. Im not in possession of any equipment to hook up and unsure where to begin with the computer. I think if I begin to mess with thing other things will break the wires are super crispy.
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