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Old 08-16-2009, 09:24 AM   #1
matzkemd
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Default Radiator cooling fans run continuously

My 2003 L200 (110k miles) is continuously running both radiator cooling fans (pusher and puller) whenever the engine is on, cold or hot, A/C on or off. They donít run with key-on/engine-off. I replaced the engine coolant temperature sensor before digging any deeper and the problem is unchanged. The temp gauge reads the same as always, the engine appears to heat up normally, and the thermostat opens at operating temp (by observing the temp gauge and feeling radiator hoses). I havenít driven the car since but the engine idles fine.

My next step was the Fan Control Module, thinking that a relay was stuck. I took the circuit board out and actuated all 5 relays: each of them happily clicked back at me so this doesnít appear to be the problem. I gave the FCM a technical tap against the workbench for good measure, no luck there either. The FCM has 10 wires: 2 large gauge wires are power in, 6 large gauge wires are power out and ground to the fans (3 each), and Iím left with 2 small gauge wires (dark blue and dark green) which read 12V with engine off and 0V with engine on and fans running.

Are these control wires from the computer? If so, what should they be reading for which fan speeds? Does the computer use the coolant temp sensor to determine fan speed?

Also, if the computer thought the engine was hot and was protecting itself, wouldnít the fans stay on after the engine shuts off (I think I remember this from our last road trip through the desert!)?

Iím open to ideas and very much appreciate any ideas you might suggest!

Thank you!

Mark

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Old 08-16-2009, 10:28 AM   #2
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Default Re: Radiator cooling fans run continuously

Answers; yes, yes, yes, and maybe. Whatever. You ask too many questions.

Does this help? (below) And as a small favor, if you fix this problem, would you post some pictures of the opened FCM? You're the only one willing to open one up and go through the pin outs and this helps me to visualize what mine looks like if I ever have to dissect one. Yes, I'm selfish. Why would I open mine when yours is already opened? Ok, ok, seriously, it may help anyone with similar fan control module issues by having at least one opened for view.

The ECM determines which fan speed to run based on the coolant sensor information. Its not likely to be the coolant sensor but somewhere between the ECM and fcm. I haven't studied the drawing yet as I felt you needed the schematic now. It gives me some time to stall for a possible answer unless somebody else knows.

BTW, I'm old school and very much a "technical rap against the workbench for good measure" kind of technician. You'd be impressed when I steam cleaned circuit boards years ago...........................and they all worked.
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Old 08-16-2009, 02:43 PM   #3
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Default Re: Radiator cooling fans run continuously

Attached are pictures of the opened L200 fan control module. I took one with the connnectors attached so wire colors are visible. According to the diagram (thank you very much!) the V6 has an extra wire and some slightly different wire colors. I labeled the control terminals for the 5 relays (from memory, but I'm pretty sure these are correct) for someone's future reference.

Thanks,

Mark
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File Type: jpg Saturn Fan Control Module Relays.jpg (150.0 KB, 144 views)

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Old 08-16-2009, 03:13 PM   #4
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Default Re: Radiator cooling fans run continuously

Thank you. The two pictures gives me, at least, a better sense of what the schematics portray.

There's a remote posibility, if you have a/c, of the combination low/high pressure switch interfering by sending incorrect signals, alerting the ECM to run the fans. Since our a/c systems will have three speeds and use both cooling fans in combination to select L, M, or H speed cooling, the a/c pressure switch may be one consideration here. The question is whether or not your a/c system is working, was being used at the time or if its disabled/broken. Other than pulling the battery negative cable or the IGN fuses to reset the ECM, I can't think of anything to have the fans running. Can you estimate what speed the fan(s) are running?

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Old 08-16-2009, 03:25 PM   #5
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Default Re: Radiator cooling fans run continuously

Thanks again for the help. Fans are running high speed. Can I disconnect the A/C pressure sensors to troubleshoot them? I hear the compressor kick on/off as I cycle the climate control: this has no affect on fan speed (currently).

I think I verified the FCM is operating correctly. I rigged some jumpers between the blue connector and the FCM (which contains the 2 control wires). The computer is trying to ground both these wires as soon as the engine is turned on (checked continuity on the meter). Playing with the jumpers verified how fan speed is selected:

Neither control wire grounded = fans off
Drk Blu wire grounded = both fans low
Drk Grn wire grounded = both fans medium
Both control wires grounded = both fans high

Problem must be outside the FCM.
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Old 08-16-2009, 04:13 PM   #6
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Default Re: Radiator cooling fans run continuously

You're good, very good. Theoretically, just shuting off the a/c should not have the pressure switch interfere with the ECM running the cooling fans but off the top of my head I think its ok to disconnect the pressure switch to isolate it from this problem. If I'm wrong you'll know before I do. The pressure switch is just another input sensor for the ECM in determining fan turn on/speed.
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File Type: jpg engine monitors.jpg (107.6 KB, 95 views)

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Old 08-16-2009, 05:59 PM   #7
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Default Re: Radiator cooling fans run continuously

Success! Unhooked the battery for 30min. On restart and test drive to town (20miles) everything works perfectly! Fans operating at normal speeds (off, then low, then medium) in 90deg weather. Thanks for the help, and I hope my explorations of the FCM can help someone else down the line.

Thanks, fdryer!

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Old 08-17-2009, 04:52 PM   #8
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Default Re: Radiator cooling fans run continuously

If the problem comes back it may be a bad Intake air Temp sensor. Have had to replace two on our 03 L-200 as soon as the sensor was replaced problem was gone. It will evently throw the check engine light.

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Old 08-24-2009, 10:28 AM   #9
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Default Re: Radiator cooling fans run continuously

I am experiencing a simuliar problem with my 2001 Saturn L-200 2.2 A/C fans. I had a service engine light last year that would go on and off when the A/C fans would run. A/C cooled, check a few things, changed FCM with new, fan relay in fuse box under hood with new, no luck, asked mechanics they said not to worry. Well this year A/C went out. Replace bad compressor, new receiver/dryer, expansion valve and high pressure switch. A/C cools but have "Service Engine" and "Service Engine Soon" lights, codes P0481 & P1640 same codes as last year. With A/C on both fans come on for about 10 seconds in High speed and then shut off and then back on 10 seconds off and on. Believe high speed is coming on because of high pressure, fans lower pressure and then shut off. I never see a low or medium speed on fans. What controls the low and medium fans? I am running out of parts to change.

THANKS

Cromy

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Old 08-24-2009, 11:02 AM   #10
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Default Re: Radiator cooling fans run continuously

Normally, the pressure switch detects and sends signal data to the ECM that determines which fan speed to run. Something's not right with the repairs to cause the same error codes. Did Saturn repair the system or a local shop? It would seem appropriate that you return back to the place that did the repairs and ask them to explain why the same errors returned.

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Old 08-24-2009, 11:57 AM   #11
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Default Re: Radiator cooling fans run continuously

Had it most done at a shop, not close to a Saturn dealer bought the car used from private owner. Car has ran great for seven years until now. All I asked them to do is get the A/C working and they did. They did not claim to or have the knowledge to troubleshoot the error codes even though the offered to help. They assisted in the code reading, code clearing and troubleshooting but we did what it said (replace A/C relay, fuse, check all ground wires, loose wires or connections, etc). So are you saying that the high pressure switch controls the fans speeds? Is there a low side pressure switch? If so where is it located? On Saturnparts website it illistrates a parts breakdown and shows a #5 Pressure Valve right next to the compressor. I dont see that, what is it and what does it do? Someone mentioned a air pressure switch going bad. Would this have anything to do with it? There is three wires going to both fans and I checked with a meter and only the high speed has voltage to it when running. No voltage to any fan wires when A/C is on until the 10 seconds of high speed.

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Old 08-24-2009, 01:35 PM   #12
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Default Re: Radiator cooling fans run continuously

The ECM (engine control module) determines which speed to run the cooling fans, not the pressure switch. If this was replaced then its not the problem. The pressure switch has the ability to read the various internal line pressures on the high side that is transmitted to the ECM.

The other pressure part is a blow-off/relief valve, not a pressure switch. Connected to the compressor, it opens mechanically when excessive pressures are developed above 500psi; this dangerous pressure level can cause physical damage if allowed to continue; this relief valve releases built up pressures to prevent damage to the compressor and output hoses. This valve does not have any electrical connections.

The cooling fans usually runs at low speed when the a/c is first turned on and as outside temperatures rises the internal a/c high side pressures rise in proportion - the fans can switch to medium or high speed. The fan speeds are automatically selected depending on how hot/high the pressures are to cool off the condenser coil/radiator otherwise overheating can result in the a/c system shutting down. If too much R134a or oil is used, this can lead to higher than normal system pressures, triggering the abnormal fan speeds. Pressure monitoring will tell if the high side is too high.

Have you tried what the original poster did, disconnected the battery negative cable for a few minutes to reset the electronics?

Last edited by fdryer; 08-24-2009 at 01:44 PM..

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Old 08-24-2009, 02:33 PM   #13
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Default Re: Radiator cooling fans run continuously

Yes tried unhooking the negative to the battery only to clear the codes (sometimes this works) have two codes P0481 (fan 2 control circuit) and P1640 (Driver 1 input voltage high). Unhooking the battery cleared the codes and the fan seemed to run longer and more often but after awhile both code lights (Service engine & Service enging soon) came on. If it is in the ECM can it be reprogrammed or repair? I hope it dont have to be replaced everything else runs GREAT.
I have no low fan speed only fast. A/C mechanic says high side pressure is correct and the fan run high when the pressure rises. He and I just cant get the fans to run in low or medium speeds..either high speed for a short period of time or off. Since the high pressure switch has been changed what else tells the ECM for fans to run in slow or medium speeds? I think the fans are good because the fans have no voltage going to them until the high speed kicks in.

Any ideas would be greatly appreciated. Saturn dealer not close. What can they do (reasonably priced) if I make the long trip?

Cromy

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Old 08-24-2009, 03:50 PM   #14
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Default Re: Radiator cooling fans run continuously

This seems to be isolated to either the fan control module (that you replaced) or the ground connection to the pusher fan (#2) located in the left lamp area. Check all the wiring connections carefully and 'exercise' them by disconnecting/connecting them and ground for any corrosion.

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Old 08-24-2009, 04:24 PM   #15
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Default Re: Radiator cooling fans run continuously

Thanks. I will check the ground but does it use the same ground for Slow and Medium speed that the High speed uses. Because the High speed works. The fan has three wires going to both fans. One wire has is grounded at all times, one wire will have 15 volts on it when the fan runs in high speed but the other wire seems to never have any measurement on it. One other member on this post spoke about a intake air temp sensor. Does this have anything to do with my problem?

Thanks again,

Cromy

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Old 08-24-2009, 05:32 PM   #16
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Default Re: Radiator cooling fans run continuously

Does this help?
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Old 08-25-2009, 10:09 AM   #17
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Default Re: Radiator cooling fans run continuously

THanks I can check a few things with this wiring diagram.

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Old 12-29-2010, 01:58 PM   #18
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Wrench Re: Radiator cooling fans run continuously

Hi, I also have a 2002 L200 with both radiator fans run continuously. Had problem for 2 days then stop. Replaced thermostat due to low heat and guess what, problem is back. I see this bug has been around for quite a while, does anyone have the fix? Anyone...?

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Old 12-29-2010, 02:37 PM   #19
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Default Re: Radiator cooling fans run continuously

Well, we have 2 L-Series in our fleet, a 2005 L300 and a 2002 L200.

The 2005 L300 fans (both the push and the pull) run on high speed whenever the A/C or defrost is on. The temperature outside makes no difference. It was so bad, that it killed our 6 month old battery because the fans cycle so often, and they draw so much power that the radio goes out.

Would appreciate any fix/input to this problem. We bought the car new in 2005, and it did not start doing this until this past summer.

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Old 12-29-2010, 04:36 PM   #20
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Post Re: Radiator cooling fans run continuously

Hi, I found the FCM in front of the battery on the 2002 L200, How do you remove it? The top cover or from the bolt on the bottom that holds the FCM assembly? Can I run my L200 with the cooling fans disconnected til the weather is warmer this coming Spring without hurting anything? I would like to look at the FCM if its not too hard to take apart/remove to check it out. Any help is appreciated...

Last edited by jdavila; 12-29-2010 at 04:43 PM..

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