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2004 Mazda 6 Sport Wagon
18 Posts
Discussion Starter · #1 ·
Hey all, figured I would post this in case anyone else has a problem with it in the future. I replaced my stock fan control module a month ago because it was broken, stuck in the “always on max” mode, which is quite annoying in winter when we’ve got single digit temps and I need the car warm. This week we’ve had some very warm days and I noticed my coolant temps were unusually higher. Initially I thought I was just a bit low on coolant, but yesterday we managed to hit 69F and by the time I made it home from work I was pushing 220F. Early that morning I noticed a burning electrical smell and when I popped the hood a got a great whiff from the fans. I took off the control module, thinking maybe I burn the connectors somehow. Well, once it was out and in front of my face, I knew it was cooked inside. So, I cracked it open…
Circuit component Passive circuit component Hardware programmer Computer hardware Electronic component

Huh, that doesn’t look very good….

Passive circuit component Circuit component Hardware programmer Electrical wiring Electronic engineering

Oh crap! And when I removed that thermal pad, the voltage regulator on the right side came up with it… including the PCB.

Anyway, posting this as a warning. Make sure where you buy from includes a warranty that covers this stuff. I got mine as a new part in a bundle of other things so I don’t have the warranty.

Now, for the electrically minded folks… let’s talk how to repair this. In my case, since the PCB is completely burnt out, it’s non repairable. But if you have the means and soldering iron, this could be repaired/improved in half an hour.

DISCLAIMER: I’m just as much as an idiot as the next person. While I have experience, nothing on the internet should be treated as infallible information. Always, always seek professional help when you aren’t sure about something. Also… this module runs your rad fans… just suck it up and buy a new one with a warranty. It’s for the best… and will cost a lot less in the long run if something breaks. I DID NOT DO THIS TO MINE! The PCB had completely burn through so all of this info below is from my experience doing electrical repairs.

Now for those still listening… let’s talk. So all in all, this is a very, very simple board. The top side of the board is mostly traces and resistors, which are the little black chips. These are easy enough to test, a simple multimeter can check impedance Between both sides of the chips.

In the group of chips, the larger black chip functions as a controller. The chances of this being bad are very slim, but checking the solder joints on each of the six legs is recommended. The back side of the board is the problem…

Whew, lots to unpack here… The design, again, very simple. Just a few caps and two voltage regulators below the thermal pad. In this case, we can clearly see the board is missing a 1000uF cap… or, well, it’s not attached. Looking below the pad shows us the micro controllers for the voltage regulators, and the right side has burned through itself. If the problem wasn’t alright obvious in this case, but it looks like the cap blew, the voltage regulator hot and cooked, and… well, it smells really, really bad.

Anyway, to fix a problem like this, the first think is to clean the board as much as possible. The heat and potential flames would easily warp the PCB, bridging points, breaking traces… and, you know, fire burns things. After a very deep alcohol cleaning, if your traces and board itself are unharmed, grab some solder and reflow the contacts for the regulator, its three legs so it’s pretty easy*. Replace your caps, and boom! Or, no boom, it shouldn’t boom. It should just work.

*In my model of this board, the regulators and all the caps are pin through points. This will potentially mean you have to clean the old solder up to get the pins through. Check you tube for desoldering videos, I’m an amateur!

Anyway, I hope this helps someone. Rule of thumb… buy it from the place with the best warranty. These things are pretty cheaply made. I wish I hadn’t thrown away my OEM original, would have loved to pop it open and see what was different about it…
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