Ok so I will try and keep this short and sweet. So as most are aware I'm sure, I have 2 fans. One kicks on when the engine reaches a certain temp (driver side). The other comes on only when ac is turned on and compressor kicks in (passenger side). The passenger side on keeps blowing fuses thus causing car to overheat when ac is on. As long as ac is off everything is fine. I replace a fuse and it lasts for about 10 minutes then blows again. It was ok but now it's getting hot.

In the picture I've posted, the 3 I circled are what I am confused about. I'm sure they are relays but why are there three? There are only two fans. Which one would be for the passenger fan? They are labeled fan cont #1, 2 & 3. Sorry the pic is blurry, not sure why. It is clear in my gallery. Never used photo bucket before...only created an account to upload this pic on here...not sure why I couldn't just upload it to the site directly.

What else could be causing the fuse to blow? I don't think it is the compressor relay because it is working fine. The fan seems to spin freely so I don't think it is the fan working too hard. If anyone has had this issue or can shed some light, I'd really appreciate it. =146393245&filters[recent]=1&sort=1&o=0]

 

Hopefully this helps you out:

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Sadly that diagram is from a 1999 MC year. The 03 Model year has only 2 25amp fuses and 3 relays. So Fan relay 2 and fan Relay 3 share Fan Fuse 2. Fan Fuse 1 is only for Relay 1.

So here is a question. Did you or someone make a change to your cars fan wiring? If they did in say the Ground area it could be that the issue is when the system tries to run in Series the system isn't able to send the 12v that would normally be ground. This then makes a Series connection and runs the fans Low. When the relays switchs for Fan High things change and the system sends power down the power line where the other fan relay makes it so the one that was passing as a though line is close and then fans run Parallel.

James

This is how the car is wired for a 00-05 Impala and Monte Carlo

 

I hate to sound like an idiot...but I am. I am sadly ignorant of all of this. I can not read the schematic. It appears to be reversed to me. Relay 1 is on the left and 3 on the right. In my car it goes 3 on the left and one on the right. So 3, 2 1. I tried to trace to the ground to no avail.

As for your question, no one has messed with the wiring as far as I know. Not since I've had the car which has been about 8 years now. My buddy mentioned to me that it could be a corroded or rusted out ground. He also said that the bushings in the fan could be seizing up and causing it to work too hard which in turn causes the fuse to blow. It spins freely tho as I mentioned in the original post. I have no idea where the ground is. I guess I'll have to try and follow wires from the fuse block and try to find it. As I mentioned it's getting hot and it is about to be time for the ac again.

 

Sorry that the Schematics are a mess from factory. Trust me when your working on a relay and looking at the diagram the relay says it is placed one way but in the car is isn't really placed that way at all. What it does is give you the Path ways of the wires. If it was to show you total path it would be a VERY large mess of wiring path even harder to understand this.

So to help some. Looking at the Diagrams in both that was offered. Fan Relay 1 in the diagram makes contact only at this time. The power goes down the line to both fans and gets the ground off fan 2 and doing this puts the fans running in Series.

Once Fans are commanded by the PCM to run in High then all 3 relays are on and the connection that was sending power from first fan though fan to the second fan. Now changes so fan 1 is running 12v full power and gets ground from other side of first motor. This also makes it so the power line for fan 2 is now on its own line running at 12v for full fan power. That is the main function of Fan Relay 2 is to change from running a Full power or 1/2 power fan speed.

Hope that helps some. if you have some good wiring of 12awg you can always test that the fans and set up a fuse of 25 amps. Set the fuse within 14in of the battery. From other end of fuse run to the Positive fan wire of fan 1 take a 12awg wire and run from ground terminal of battery to the ground side of fan 1. Test for the time that your car can run without blowing the fuse and see if the fuse blows. If not then move it over to the next fan and test again same as before. If there is a Fault with your fan it should blow the fuse as well.

Problem is you would have to know was the Fan state in High or Low when the Fuse went. If it was in fan 2 then it is a little easier to trouble shoot the bad fan. However if the Fan 1 fuse is what is blowing it could be hard to know high or low. Where fan 2 3 fuse only powers on the High state.

Hope something was found useful here.
James

About the ground. there is only 1 ground with a common Splice Point for both fans. I don't think it is bad ground. If bad ground it wouldn't turn fans in either state high or low or would blow fuses of both. It could be a bad fan. However I would look over the grounds and clean and re seat the ground to make sure.

 

Was going to edit again but that just becomes a mess or hard to follow if your reading not logged in. So I will add this here...

if your fan 1 Fuse is blowing. It could be Relay 2 that is a 5 pin Relay could be at fault or not getting power at the Switch. So when Fan 1 is running in Low. PCM says Go high relay 3 kicks in but don't change over fan 2 relay could make so one or the other fuse blows as well. So it could be a Relay as fault.

Problem is, Without Having a Good Testing OBD II scanner that can command BCM and PCM to do things when you want them to it is hard to check for faults on your own. Having the right tools can have the tool tell the PCM to switch on fan 1 relay to run them in Series as normal low state. Then tool can tell PCM to command High state. At this time it would be something we would know what state the command is in to know where the issue is.

There is some other testing that I would do if it was my car. This would tell me when and where the main issue is. However it isn't smart and Because I am not there in control of the car I don't want to say run your car in this state because it could cause other damage.

I will offer this. IF you know how Relays work and see something you could do in testing over Fan 2 relay area of the system always work safe and with fused test wires.

Please note this Fan system is Running in Low 6volt state over 2 fan when run in Low. Just like the DRL of our cars when the DRL is on. In the High state Fan 2 Relay moves the ground for Fan 1 from Pulling though fan2 to ground and Fan 3 Relay now gives voltage to fan 2 for both fans to run full power.

Info about Relays incase you don't know 100% how they work. Pull one out on the bottom it will be numbered for 4 Pin 85 and 86; 87 and 30. So 85 and 86 are the coil side AKA Control. Most times a Relay will have Main power on 30 Pin and when Relay is clicked on the Power from 30 goes out to 87. In some cases where there is no need for main power to be at 30 they can put the main power on 87 pin and out down 30.

On Fan Realy 2 it is the same as above however there is now an Extra Pin for 5 Pins with added Pin 87a. So when 87a is present in a diagram. 30 and 87a rest until the coil side is hot then it moves 30 up to 87.