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March 31, 2002

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DIY Merkur heater blower fix...

March 31, 2002

Okay, so the Merkur lists claim that 9 times out of 10, a fucked-up heater blower in a Scorpio is the fault of a blown power transistor.

Sure enough, I was in with the majority, and had the option of driving around this winter with my heater blower jumpered on high speed or not running at all...

Just in time for me to turn on the air conditioning, the Merkurbeast has a functional heater blower!

With the aid of a $9.00 power transistor, the fan once again blows at the variable speeds that the wacky German engineers who made my car planned for it to blow at.

They must have had a sense of humour as well, as they booby-trapped one of the two screws that held on the blown power transistor (this was well-documented on many a Merkur mailing list, but The Paperless One broke the trick screw anyway, opting for the "drill a hole, solder a wire, and route it through the die cast cover of the module" routine, which is more user-friendly, should my module blow another power transistor).

Nine bucks certainly beats the several hundred I was anticipating when the heater blower stopped working in the middle of the winter.

Scorpio heater control module

BTW, a suitable 2N3771 power transistor replacement is the NTE 181 high-power audio amp transistor, or the ECG181.

Here's what someone in the know said about this power transistor:

NTE's replacement, NTE181, is an improved version of the 2N3771 and carries 90 volts instead of the 40 volts and can dissipate 200W instead of 2N3771's 150W.

Happy fixing.

Maybe it will break again, so that I can take photos. As for this time, I just forgot - I was so excited to have my much-awaited power transistor that I forgot all about the camera...so there's a generic photo that shows the die cast bit and the power transistor on the top!

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