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Old 09-20-2010, 04:05 PM   #1
provisor
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Default Radiator Fan Not Turning On

My car has been running a lot hotter recently. My cousin and I have determined the radiator fan does not come on at all unless the air conditioning is turned on.

I have a 1998 Saturn SL2. We replaced the old radiator fan to be sure that it wasn't the issue, we've also replaced the relay's, flushed the coolant, and replaced the thermostat, but that fan refuses to come on unless I have the AC running. If I don't switch the AC on and the car is on but parked, or I'm sitting at a light, the car will slowly overheat--but on the highway it just runs hot (much hotter than normal, but not enough to overheat).

Any suggestions on what the problem might be, or what to check next are greatly appreciated.
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Old 09-20-2010, 04:46 PM   #2
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Default Re: Radiator Fan Not Turning On

Some more info needed......
Has the coolant temp sensor been replaced?
What does the temp gauge read?
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Old 09-20-2010, 04:51 PM   #3
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Default Re: Radiator Fan Not Turning On

Replace the ECTS.

How-To Library http://www.saturnfans.com/forums/forumdisplay.php?f=26

Video: http://www.youtube.com/watch?v=pUwCTJRqnAk
http://www.youtube.com/watch?v=JC0U53w_Htk

That is what turns the fan on when the engine is actually hot. The fact the fan comes on with the A/C shows that all the other circuitry is functioning properly. The ECTS is a $10.00 part at the parts store.
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Old 09-21-2010, 05:21 AM   #4
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Default Re: Radiator Fan Not Turning On

I had the same problem. I replaced my ECTS (electronic coolant temperature sensor), but it didn't help. I've concluded it's a problem with the ECU (engine control unit, aka main computer), which is very expensive to replace.

Since the car otherwise runs fine, I opted for a custom fan thermostat. You can buy them at AutoZone for $19. They're made for aftermarket/universal fans. Here's how I did it:

All you do is take off the main radiator hose (at top right of radiator), insert the sensor probe into the hose, placing the included foam piece (which I had to cut in half to fit) in between the "capillary tube" and the radiator itself to prevent corrosion and leaks. Make sure the tube isn't kinked!

Then just run the wiring so that instead of triggering the fan itself, it triggers the fan relay (which works, since the A/C triggers it). Instead of wiring it to send power to the relay, simply wire one end to the proper terminal of the fan relay (when standing at the driver side looking at the main fusebox, it's the terminal closest to you), then wire the other end (the other terminal of the thermostat box) to a ground somewhere (NOT an exterior fender bolt--the hood will crush the wire when it closes; I used the headlight assembly bolt, making sure it's clear of all headlight wires).

All you have to do then is mount the control unit somewhere (I epoxied it to the inside fender wall), then use the thermostat like you do for a house air conditioner. Fine tune it the way you like, then you're all set!

There are many threads on such a subject, but this is how I did it. I use this on my daily driver of 100+ total miles/day and it works great with no leaks. Just make sure the thermostat unit (the box with the knob) doesn't get wet, or the contacts will short and the fan will never turn off (until it dries). Also, the fan will stay running for 1-3 minutes after the ignition is switched off. This is normal (although people will think you left your engine running ).

I'll try to post pictures tomorrow of my setup!

Last edited by Equalyzer; 09-21-2010 at 05:26 AM.
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Old 09-21-2010, 05:37 AM   #5
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Default Re: Radiator Fan Not Turning On

One important note about replacing the ECTS: use a deep socket to take it out, and tighten by hand at first! I used the socket wrench at first to tighten it, wasn't careful and unknowingly crossthreaded it, then broke the threaded piece off inside the engine block! I had to get a neighbor with a machine shop to use an easy-out, then retap the threads on the engine.

Luckily, I had a neighbor to help instead of a hack shop telling me rethreading was impossible and I needed a new engine (I've had places tell me that, believe it or not). Long story short, take your time and don't crossthread!! The relatively soft aluminum in the block gives you no warning resistance if you tighten it wrong. Better to be safe than sorry (sorry=car out of commission).
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Old 09-21-2010, 07:08 AM   #6
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Default Re: Radiator Fan Not Turning On

When you say hotter - where is the needle, 1/2, 3/4 way mark?
Do replace the ECTS with a brass tipped saturn one.
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Old 09-21-2010, 07:29 AM   #7
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Default Re: Radiator Fan Not Turning On

Slowly overheat? Over heat mean temp gauge in the RED zone. If the temp gauge is climbing to this area, your ECTS may not be totally bad - a bad ECTS typically reads lower temperature. But replace it with a new brass tip model if it has not already been replaced.

Fan turn on for '96 and later models is just before the temp gauge reach 3/4 scale. Is it getting that high?

Normal temp on the open level road is about 3/8 scale, higher if the engine is under heavy load (e.g., a long hill climb in 3rd or 4th gear) and the A/C is off and/or perhaps a very hot day.
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Old 09-22-2010, 03:01 AM   #8
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Default Re: Radiator Fan Not Turning On

1/4 to 3/8 on the temp gauge was about normal before I overheated last month. Since then, when car is on and stopped it will slowly rise until it reaches the red zone. When I'm on the highway, it will usually stay steady at 1/2.

Forgive me for being uninformed, but I don't know what the temp sensor is. Unless that's a synonym for engine thermostat, the temp sensor has not been replaced. Because so many people have suggested I replace the ECTS, that's where my cousin and I plan on starting.

Thanks for the input everybody. I will re-post as soon as I replace the ECTS.
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Old 09-22-2010, 04:18 AM   #9
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Default Re: Radiator Fan Not Turning On

You probably do not have anything wrong.

Have you tried physically taking the temperature? Get a thermometer and stick it in you coolant reservoir (I used a digital cooking thermometer.) Let the car run and the fan should kick on when the temp hits 220 degrees.

I thought I had the same problem for about a year. I noticed that the temp gauge seemed to be running a lot hotter than normal. I never remembered it going past 1/4, and now it was going past 5/8. I would start to panic, turn on the heat in the summer as the gauge started to climb and avoid any type of traffic jam. I eventually took the temp and realized there was nothing wrong.
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Old 09-22-2010, 06:03 AM   #10
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Default Re: Radiator Fan Not Turning On

Quote:
Originally Posted by provisor View Post
... Forgive me for being uninformed, but I don't know what the temp sensor is. Unless that's a synonym for engine thermostat, the temp sensor has not been replaced. Because so many people have suggested I replace the ECTS, that's where my cousin and I plan on starting...Thanks for the input everybody. I will re-post as soon as I replace the ECTS.
Just so you don't have the two confused, the coolant thermostat regulates the engine coolant operating temperatures while the coolant sensor is the electronic sensor strictly for the engine computer to know engine coolant temperature. The original plastic sensor fails and tends to run the engine rich mixtures while never allowing the cooling fan to turn on. You can tell which one you have by the profile; use the Forum Jump below to find the How-to tab and look at the side by side pictures of old plastic tipped ones against the brass blunt tipped ones. Once replaced with a brass one the temperature needle will rise to the 3/8ths mark and not turn on the cooling fan until reaching just shy of the redline.
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Old 09-22-2010, 08:34 AM   #11
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Default Re: Radiator Fan Not Turning On

On a '98 shouldn't the fan come on just before the 3/4 mark on the temp gauge. When replacing the sensor, check to be sure the conenctor is free of corrosion. Note that by now a fair number may have had the sensor replaced.

If the gauge is going into the red zone something else may be amiss because the temp gauge and the fan turn-on are both driven from the ECTS reading . However, still worth checking the ECTS and replacing if the resin tip type.
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Old 09-22-2010, 01:29 PM   #12
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Default Re: Radiator Fan Not Turning On

On a 98 the fan comes on between 9/16 and 11/16 accounting for sensor and gauge tolerances. call it 5/8 so it can be eyeballed. The PCM assumes that the information from the sensor is correct.

When the signal into the PCM reaches the predetermined level the FAN will come on if it will run when A/C is selected. If the gauge reaches the RED zone and the fan is not on then there is a problem.

Before jumping to conclusions it is required to find out if the gauge is providing accurate information. This is easy to do by comparing the gauge indication against the actual temperature of the coolant returned to the reservoir by the small continuous vent line with a kitchen meat thermometer.
This link will provide the actual coolant temperature vs. gauge indication.
http://www.saturnfans.com/photos/sho...ding/cat/12963

If the coolant concentration is correct it will not boil with the reservoir cap off till 225F at a true 50% concentration. So, don't let the return to go much over 215F before putting the cap back on.
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Old 10-11-2010, 03:47 AM   #13
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Default Re: Radiator Fan Not Turning On

...Sorry I'm so late, but here are some pics of my custom fan thermostat. The pic on the right shows the probe inside the radiator hose. This photo was taken about six months after I installed it, and it still doesn't leak!

Note the wire goes into the fan relay at the top, opposite from you. My mistake earlier. The wire going into the fog light relay is for a switch that operates them independently.
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Old 01-12-2014, 04:56 PM   #14
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Default Re: Radiator Fan Not Turning On

I am having the same problem on my gf's car.

She has a 1998 SW1(or 2?) with the fan not turning on.

I just took out the entire fan to test the fan and it appears to be dead.

However, I also took a multimeter and attached the leads to the fan connector. Turned on the engine, turned on A/C full blast and recirc, the multimeter still read 0 VDC.

So it appears I have a dead fan, and either a bad relay, fuse, or ECTS sensor.

So easy thing first, where the hell is the fuse located? Is it in the engine bay, or is in the block next to the passenger seat? I know where the relay is already.

Thanks.
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Old 01-12-2014, 05:42 PM   #15
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Default Re: Radiator Fan Not Turning On

Back up a little on your troubleshooting. When you turned on a/c did you actually see, hear and feel cold air or the compressor engage? If the compressor doesn't power up then the cooling fan won't turn on; any leak or damage that prevents the a/c compressor from powering up also means the cooling fan will not turn on. Do not assume turning on a/c will turn on the fan unless you verified the compressor engaged.

The easiest and best way to troubleshoot a cooling fan issue is to check the coolant sensor first. Is it the faulty original round nosed plastic one or the revised flat nosed brass one? Do this first before jumping into fan/fuse/relay problems.
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Old 01-12-2014, 06:43 PM   #16
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Default Re: Radiator Fan Not Turning On

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Originally Posted by fdryer View Post
Back up a little on your troubleshooting. When you turned on a/c did you actually see, hear and feel cold air or the compressor engage? If the compressor doesn't power up then the cooling fan won't turn on; any leak or damage that prevents the a/c compressor from powering up also means the cooling fan will not turn on. Do not assume turning on a/c will turn on the fan unless you verified the compressor engaged.

The easiest and best way to troubleshoot a cooling fan issue is to check the coolant sensor first. Is it the faulty original round nosed plastic one or the revised flat nosed brass one? Do this first before jumping into fan/fuse/relay problems.
Yeh the condensor is definitely turning on. Well I'll do the ECTS sensor first then since it's only $10, then I'll see if I then have 12 volts at the fan connector.
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Old 01-12-2014, 10:35 PM   #17
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Default Re: Radiator Fan Not Turning On

^^Compressor, not the condenser^^
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Old 01-14-2014, 11:12 PM   #18
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Default Re: Radiator Fan Not Turning On

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^^Compressor, not the condenser^^
Same difference...
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Old 01-20-2014, 09:23 AM   #19
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Default Re: Radiator Fan Not Turning On

^^^ I beg to differ:
The compressor is belt driven, the condenser is passive, a thin radiator in front of our coolant radiator.
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Old 03-18-2014, 02:39 PM   #20
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Default Re: Radiator Fan Not Turning On

Well I just changed out the ects sensor and fan relay. Turned on the ac full blast and recirc and still the fan didn't turn. I will test the fan connector again though to see if I now have 12 volts.
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