I have pretty much determined this little finned box just forward of the battery is causing my no-blow-fan intermittent behavior. I put a voltmeter on the white and blue control wire from the main ECU and watched it go up and down under various conditions. With only 4-6 volts showing, the fans came on kind of slow but enough to cool things down then shut off. I had about given up on trying to see how it was failing then today with ambient temp at 102, and the A/C brought on at a dead stop, the fans failed to come on at all. The voltmeter was showing hefty 10-11 volts but zero rotation. My theory is that when the ambient temp is really high, and the A/C is put on and the condenser sensor asks for full rotation, the little amplifier craps out. Just when you need it most, it can't deliver. So has anybody replaced one of these himself? Does the battery have to be removed to gain access or will it be possible to get it free in that cramped space? Thank you.

 

Thomas, do you have to remove the battery, no. Does it make the job easy, obviously. The big problem that you are going to find is that you can't just get the fan controller in most cases, even through a junk yard. You will have to get the complete fan assembly (controller and 2 fans). So, obviously, that is going to run you a bit more.

Replacement is not that hard. Take your time and make sure it is all done correctly. On a side note, if you are just going to throw out the old controller, could you send me that controller. I am looking for an old one to see what the failure mode is so I can possibly come up with a way to upgrade these boxes and put out a fix for those that are willing to play and fix their own vehicles.

P.S. Thanks for your town's caring. I served on the USS Tucson for 3 years and you guys and gals know how to keep us sailor happy.

 

I got my replacement through Nationwide Auto Recyclers. I bought the complete fan assembly from a 2004 X for $100 and just used the control module. This was around $300 cheaper than a new unit plus for the new units you must buy a wiring harness adapter because the new ones don't match the old wiring that's an additional $75. It's not really hard to do the change up if your hands are not too large, that is because to get to the plug for the right side fan is a little tight but doable. Like Thermo said it can be done with the battery in place but much easier with it out. I would say it took me less than 1/2 hour to do the job.
The only real problem is find the replacement for a reasonable price.

 

I am super afraid of removing battery due to electronic reboot problems. I do not have the radio code to re-enter for one!
And to THERMO: I cannot take any credit for the compliment you provide based on your naval ship experience but I am glad you had a good experience. I was never in the armed services but completely support all who have been there and done the heavy lifting.
I did buy a controller used from welsh in ohio; I shall report on failure mode analysis later once I get the replacement in later next week.
Thank you.

 

Thomas, not a problem. Just let those in your town know that those of us on the ship do appreciate what they do. The mexican food is outstanding!!!!!!!

Now, on to the bigger issue of reconnecting the battery. If you are truely worried about reconnecting the battery. What I would tell you to do is to go to Radio Shack and get a 10 ohm, 1 watt resistor. This will cost you like $1.19. Now, with both battery terminals disconnected, place the battery in the car. Now, connect up the positive wire to the positive battery post and tighten down. Now, bring the negative battery wire near the negative battery post and then slide the resistor in between the wire and the battery post. The resistor will limit any spike the car sees. After a second or two of holding the resistor in place, you can push the negative wire down on to the battery post, pushing the resistor out of the way. Don't worry if the resistor falls out of the way for a second or so. As long as all of your doors are shut (ie, interior lights are off), the computers will have enough power left in them that it won't be an issue. Once the wire is on the battery, tighten down.

Now, for the radio code. Stop by your local Jag dealership and talk with one of the service guys. They should be able to look up your VIN and get you the radio code. All you will need to do is to have a photo ID and your car's registration.

 

I've never had a problem dis-connecting and re-connecting the battery in my X and I've done this several times. As far as needing the radio code you have enough time to do most small jobs without having a problem in this area, right off the top of my head I can't recall the exact amount of time before the radio is affected. I know I've had the battery dis-connected for around an hour with no problem.

 

I have to come along again, because I haven't got any right solution for the overheating problem and I suppose Cooling fan control box is the issue, I got another one through this forum but unfortunately it won't work either it's even a little worse than my original is... Is there anyone who have opened this box successfully, I need a quick solution because I should travel in few days to Norway and there is steep uphills all the way and I'm afraid to fry my engine without properly working cooling fans.

 

Blackcat, there was a member that opened up the box and based on what I saw from the inside of the box, you will see 4 "black boxes" on the one end lined up side by side. They are high power transistors. You would need to replace all 4 of them to get a pretty good "blind shot" at fixing the modules. I am looking to get my hands on a bad module so I can use my test equipment to figure out what component(s) are bad and then be able to give a step by step on what to fix. But, unfortunately, I haven't been offered a bad one yet. So, if you know someone with a bad one, please let me know.

If you look on the transistors, there is a part number. I found them through E-bay for around $2 each. But, normally you have to buy like 10 of them for the order. Much more than that, I can't help you.

 

Ok, so I will open that worse one and measure all the components, I will tell you what happened and does it work...

 

I am the guy who started the thread and took my box apart and posted images in an album. Personally, I would not waste time testing the pieces in the box. Under load, they will not behave as they do static. Some day when I have nothing to do, I will replace the four active solid state devices and the large electrolytic caps. If I were you, Blackcat, I would just replace those items and put it back in service. Did you read my original details about the voltages on the control wire? I would ascertain first if the main ECU and temp sensor are indeed sending the right control signals to your box. Good luck.

 

You are absolutely right Thomash, there is no sense to test those components without right control voltage, there is no logic with those three hexfet transistors and I just replace them one of those four is double diode.
I haven't even thought that there is temp sensor to give certain control voltage, this might be one possible malfunction point also, I was a little bit surprised how complex this little computer is, yes there was a little processor in it also. By the way does anyone know if there's any replacement part with this box and how much does it rape my wallet?

 

No, there isn't a new replacement fan control module. If you want new you have to buy what is called Cooling Fan Shroud Assembly, which consists of the shroud, fans and control module. Then you need to buy a Wiring Harness Adapter, because the new harness on the assembly doesn't match up with the old harness in you car. This set up will cost $400+.
The best way is to try and find a used control module and hope that it is good. I found a complete assembly when I did mine for $100 and just swapped the control modules

 

I did find a used module in eastern US for $100 and it works perfectly.
Regarding the sensor: from what I can tell, there is just the one coolant sensor at the front end of the motor on top. It talks to the ECU which uses that info to deflect the gauge on the dash, set mixture and generate the varying pulse width for the fan controller. I am not certain about how the A/C is integrated into this but I believe that the freon pressure sensor acts on the pulse width modulation (via ECU). And for what this is worth, I would suggest that at any speed over 40 MPH, the fans are superfluous. There is more than enough air to cool everything as long as you are moving steadily and fast.