Question about 2001 Chevrolet Monte Carlo

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Driver side cooling fan was working and passenger side was not, switched 4 pin relays around multiple times, now passenger fan works and driver side does not work and I can't get the driver side to work by switching relays. Runs hot, uses coolant and oil, runs about 170-185 as long as the car is moving, runs at 200-230 while idle, checked all fuses and they are fine. Thought maybe it was the relays, thermostat or the water pump if it was replaced with a non-original part.

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  • ggrinolds Feb 07, 2010

    I'm pretty sure it is not the fan motor connections. I originally thought the fan motor was out on the passenger side but when I switched out the relays, the passenger side fan came on when I turned the AC on and when the engine got hot.

    Before I originally switched them, the driver side fan worked and the passenger side did not work. Then when I switched them, the passenger side worked and the driver side did not work. No matter how many times I switched them back and forth, the driver side still will not work at all now and only the passenger side works now. I switched the two 4 pin relays out with 2 that do work from the fuse boxes inside the car and nothing has changed.

    Could the 5 pin control relay in the middle be bad and still let one of the fans work?

    Is it possible some of the sensors could be out that tell the fans to come on when the engine gets hot?

  • ggrinolds Feb 08, 2010

    It's a 3.8 V6. Did you get my last response with the questions about the fans? I was wondering if one of the fans would still work if the 5 pin control relay was not working.

  • ggrinolds Feb 08, 2010

    I know it's not the fan motors. It has to either be the connections on the fuse box or the 5 pin control relay. Yes, the relays I switched out had the same number on them, 3604 I think. I got a 5 pin relay last night, 3602 I think but they gave me the wrong one, so I need to take it back tonight and I will let you know how that works.

  • ggrinolds Feb 09, 2010

    I replaced the 5 pin relay and no change. I took the plastic cover off of the motor and I saw fresh coolant on the motor near the thermostat so it looks like I'm going to have to replace the head gasket, thermostat and flush the radiator. Any idea what a reasonable price would be to do this on a 2001 Monte Carlo SS 3.8? Doesn't look like there is too much to take apart to get the the head cover off on this motor but it would be nice to know what a fair price would be.

    If the coolant is fresh, would this be coming from the thermostat or some other source? It does appear that there is some sludge coming from the head cover gasket but very little, mostly fresh coolant. I have not had any oil stains in the driveway so I'm thinking it is a small leak.

    If I replace the head gasket, thermostat and flush the radiator, is it possible I can use the green coolant instead of the Dex-Cool? This seems to be an issue on GM vehicles.



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The coolant sensor controls these fans,one is for moderate cooling,the other kicks in when the temp gets up higher,so change the coolant sensor.Turn the ac on max cool,see if the cooling fans both come on,and let me know.

Posted on Feb 10, 2010

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Well your coolant temp sensor/ sender is what tells it to turn on but that shouldnt be the prob. i would test the connection when the fan is running chances are the motor isnt getting a good connection. or the motor is bad.

Posted on Feb 08, 2010

  • jwtbagger Feb 09, 2010

    to do a quick test on that start your vehicle and set the climate control to defrost that should turn your fans on at the same time that would determine the main control relay/5 pin relay.

  • jwtbagger Feb 09, 2010

    or while the car is running then disconnect the temp sensor your fans should run.


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First when you remove the cooling fan relays take a close look at the terminals where the relays go into and make sure they are not corroded and make sure they are making good contact on the terminals.Also you can remove the fuse and relay holder and look underneath where the wiring is and make sure all is good there to.Do the same on the with the fans make sure the terminals are making good contact with the fan motor terminals.The other thing is if you are just swapping the relays you could be moving the bad one from one spot to another.Might have to replace them with new ones.Some times if you wiggle them around you can tell which one is giving you the problem.If you know how to use a digital multimeter you can ohm the wires that go to the fans.Try this and let me know if you need more help.Good luck.

Posted on Feb 07, 2010

  • Salvador Quintanilla Feb 07, 2010

    The fans are controlled by the pcm which gets it`s info from the coolant sensor.You can check the connections on the coolant sensor.I forgot to ask what motor you have.The 3.1 or the 3.8?The coolant sensor has black and yellow wire connector.Also check the grounds and make sure they are clean.One thing you could try if you think the motor might be the problem is use a fused jumper and a ground from the battery to the motor that does not work.Use the fuse on the positive side wire.If the motor does not come on then you know it is the motor.If it does come on then you know the motor is good.Make sure and check under the fuse relay center and make sure the wires do not look green and corroded.One other thing is it could be the pcm.Powertrain control module.

  • Salvador Quintanilla Feb 08, 2010

    Yes it can still work because the fans work off of all 3 relays.Check the fuse for the cooling fan that is not working and make sure it did not blow.The PCM controls the ground circuit for the cooling fans from info from the temperature sensor.Depending on the temperature of the coolant the PCM could turn the fans on low or hi speed.The other thing with the relays is the ones that you swapped.Were they exactly the same as the ones that you took off?G.M.uses different relays on there vehicles.If the numbers on the relays were not the same then this could not have been a good thing to try.What a technician would do first is install a scan tool and then command the fans on with the scan tool and make sure the fans are good.The other thing he can do with the scan tool is drive the vehicle and see at what temp.the engine starts to get hot and also see if the fans are coming on at the specified temp.Then he checks to see if there are any codes in the cooling system.This way if there are any codes they will usually lead you to the problem or the area of the problem.Then he also checks for loose,or corroded wires or connections.It`s not always easy to help people because you don`t how much they can do or if they know how to use for example a test light,or multimeter,install a fused jumper wire or if they have the availability of a scan tool and know how to use it.


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Which Relay/Fuse controls the power windows?

Did you check for battery voltage at the switch , with a volt meter before you replaced the main driver door switch ? Maybe you'll want to take this to pro ,instead of just replacing parts !
Symptom Chart Condition Possible Sources Action
  • No communication with the smart junction box (SJB)
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  • REFER to Section 419-10 .
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REPAIR the circuit. TEST the system for normal operation.

Mar 24, 2015 | 2004 Mercury Sable

1 Answer

Why won't my cooling fan turn on (swapped thermostat, thermoswitch, fan really)(fans work when hard wired to battery). Causes car to overheat in idle.

depending on the year, there should be 3 relays that control the fans.
There's a rad fan relay (4 pins), an a/c condensor fan relay (4 pins), and a fan control relay (5 pins). This allows them to be run at low speed or high speed. Check the grounds behind/under the righthand headlamp.
Check Fuses 57, 58 (30 Amps) and fuse 46 (15A) under the hood, and fuse 3 (7.5 Amps) in the driver's underdash fusebox.

May 18, 2014 | Honda Pilot Cars & Trucks

1 Answer

All of the passenger window are not working (probably the issue started at the same time), do not roll down or up, no issues with the driver window. Driver side switch for all the passenger windows makes a...

windows (all) power windows. its a fuse. blown.
this is in the operators guide, lost?

fuses that look bad , are
fuses that look good, can be bad, (tiny cracks. ) we never assume we tests them.
and the FSM covers this, why fix cars, FSM free,?
or go to and read that. its all there, and the full schematic for your car 50 pages. just on schem.
im looking now...for you..... tick tock tick tock ok. 30seconds
and ...
usa mode is unique as is 4 door, so i guess..
4 fuse, under dash, fuse #24,25,26,27.
the fuse box door relay is control by the DCMU.
door metrix control unit (brain)
if the relay dont click the relay is bad, or the DCMU is bad, or the inputs to the DCMU are fibbing (rules of computers apply)
if all are dead its not the door motors.

pin 10 must be 12v. at all times, even key out.
pin 3 goes to 0vdc energize the relay, if not the relay will be dead.
when you actvate any window switch this pin3 goes low.

there are 5 switches , and one called main, this switch must work
or all is dead. (really its a parent switch blocking kids)
this switch if not closing, kills the other 3 switches dead,
it holds 0v , to do that. a ground,
any switch stuck my cause the DCMU to go funky, as is with many computers, the unit might just dummy up (GIGO rules)
GIGO in computer parlance is "garbage in , nets,. garbage out)
is always possible.
keep in mind most makers dont publish the truth table. (sigh)
the brings us to the captains seat.
one trick is to unplug all non drivers (captain switch) and see if captain switch now works,
if yes, bingo on others. bad, retest to find bad one.
the drivers switch has 5 modes, and 8 wires
my book does not show the logic on these, but id bet a real FSM does.
try ON postion and test all other doors,
the try autodown, does driver window drop?
my book is weak,
but above might help.

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1 Answer

2003 chevy monte carlo passenger side cooling fan not working

The passenger side fan should only come on while driving at highway speeds, to offer additional cooling help to cool down car, the Driver side fan is for when parked, ideling, city traffic, and air conditioner use. At least that is what i was told.

Jul 07, 2012 | 2003 Chevrolet Monte Carlo

1 Answer

Chevy Impala 2003. Replaced cooling radiator cooling fan. Fan now works (driver side). Hooked up code reader. Received code for cooling fan removed code because fan was replaced. Next day engine light is...

is the passenger side coming on? it is possible that it is setting the code for different speeds also. may want to check the cooling fan relays.

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My radiator fan is not working and I cannot find any of the relay fuses I have seen in other cars for this type of problem.

Follow the wiring back from the fan motor, the relay is often found at about the height of the bottom of the radiator on the inner fender. Check that connection is clean and free of corrosion. Check that the fan works by taking two trailing wires directly from the bettery terminals and connecting then to the fan motor directly. Use a voltmeter and check the voltage at the relay when engine is cold and shortly after the radiator top hose from the engine becomes hot (the coolant sensor should have signalled for the fan to switch on at this time). No voltage indicates a break in the circuit or faulty sensor. Voltage but no fan indicates faulty relay

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Where would the relay switches be for the cooling fan

under the hood, driver side (usually) firewall behind battery. (passenger side if battery is there). Look at the back of the relay box cover for diagram. If there is none refer to repair manual for diagram.


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Apr 27, 2010 | 2002 Jeep Grand Cherokee

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Where in the heck is the radiator fuses on a 2003 chevy monte carlo SS. The passenger side fan motor has quit but is showing it has power when tested with a testing light?

if you have power there then the fuses are good or relays but if you have power then you ethier have a bad fan or ground wire also that fan should only come on when the ac is on

Aug 27, 2009 | 2003 Chevrolet Monte Carlo

1 Answer

I am trying to locate the relay panel on my 99 vw passat 2.8 gls. My electric cooling fan was broken so I replaced it last night and tested it on the battery to verify it works- but it is not getting power...

open the drivers door .. on the end of the dash (normally covered by the door) is a panel .. pop off that panel and the fuses are there .. of course fix the problem that caused the wires to burn then locate the fuse .. not easy since they give you a really cryptic guide to the fuses .. of course you should be able to see one thats blown .. if you cant read the gliphs then call a dealer to find out which fuse is which .. the relays are also behind the fuses .. again not marked except by big numbers stamped on each but no guide .. there are two fans .. the driver side is the cooling fan ..the passenger side is the air conditioner .. that is operated by a pressure switch in front of the condenser (front of car under gril on passenger side) .. .. likely a coolant temp switch operates the cooling fan .. actually i can check that if you need more info ..

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Cooling fan relay not working

The relay is easily replaceable. Either a gray or black box located on the passenger side, front of the engine compartment mounted to the frame that the radiator mounts to as well, there should be 4(that's how many my 94 Century 3.0L has) of the relays side by side, readily visible when you open the hood. Using a new relay, you can test each relay one at a time switching them out, until you find which one activates your cooling fan. On the flip side, it is an electric fan, so it only turns on typically when your engine exceeds 200+ (i think it's 225) degrees, or you activate the a/c on max setting, so maybe it's possible that it does operate under those conditions, but you're not able to witness it...? good luck, I chased that issue on my Century for quite some time...

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