G'day, This also happened to me a couple of months back in my VS stateo, my fan wouldn’t turn off after the ignition was off, and the quickest way I could stop the fan from draining my battery was to do as some of you other guys had suggested and pull the fuse.
I have also seen posts about the problem on other sites and I found out a few things while trying to fix my car so I’ll be nice and share.
· My car runs climate so I have a fan amplifier circuit and not a resistor, and depending on how the transistor blows will depend on what symptoms you get. If it blows short circuit, then the fan will only run on high speed even when you select a lower speed, and will not shut off with the ignition – the only way to stop the fan is the pull the fuse. If it blows open circuit you will lose all of your low fan speeds and only the high speed will work (this would also be a symptom of non-climate vehicles) because the high setting runs through a relay aswell as the amplifier.
· When I told the Holden parts guy what was wrong, he said the relay must be buggered, because the amplifier can only blow open circuit….yeah right, he was referring to the resistor, so be careful of advise.
· Another thing that caused me much pain was the wiring diagrams in the service manual I have (VN V8) show the amplifier circuit with a transistor in it, it’s wrong, it is a MOSFET not a transistor.
· You wont find a replacement MOSFET by the markings on the device, it’s marked, NEC D1297, after much searching on the net and checking out suppliers, I’m pretty certain the D1297 is special marking NEC have provided for a special Holden only run of parts, you wont be able to buy it anywhere, and I don’t know what it’s real part number is and doubt that it would even be available to component suppliers.
· Climate cars use a weird control circuit that I still haven’t got my head around, but I don’t exactly know what is in the ECCU, knowing that may shed some light. Non-climate cars are pretty straight forward, either the resistor is blown or it’s not.
So I finally got around to fixing it a couple of weeks ago and it been working perfectly. If your handy with a soldering iron you can replace the MOSFET that’s in there with any number of parts, I had some smaller MOSFETs at home that are pretty robust and is so far doing the job quite well. They are smaller in size but have adequate current handling capabilities, about 75Amps, they are probably a little overkill, but it’s all I had on me - and you wont find them at dick smith and the like. If you wanted to try something out of tricky dicky, I’d go with the BUK456-60A/H (cat No. Z1820), or RS components have a heap of parts that would do the trick, maybe try MTP75N05HD (stock No. 177-2576), they are both around $10. These parts will get quite warm once they are screwed into place but they should be OK because when they a working they constantly have a fan blowing air onto their heatsink. It probably takes an hour to do if you have the right tools, but it beats donating $160 to your local Holden dealer.
Happy hankering.
