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View Full Version : Blower motor problems - 1993 740il


bill_rowe2001
08-15-2008, 06:49 AM
Well, my mechanic chose not to listen to me this week. I told him the problem with my 1993 BMW 740il is that the blower motor periodically works and doesn't work. When it is working the speed controls work fine. When it isn't working it isn't working on any speed. So, against my better judgment, my mechanic chose to replace the most expensive item on the list, the blower motor resistor. Luckily he was able to find a rebuilt resistor, so instead of almost $800.00 for the part, he only spent $293.95. However, the problem still exists. In fact, I went to pick up the car and immediately discovered that the problem had not been fixed.

So, now I am looking at even more repair bills, and will it be fixed this time? The mechanic said he will do some research online and hopefully come up with a solution. But, with the transmission service and new fan shroud and new resistor, I've already spent over $1100.00, and the real problem (a blower motor that works only when it wants to) still exists.

If anyone out there is familiar with this problem, please give me some insight as to the real repair. Thank you very much!

TerryY
08-16-2008, 05:07 PM
There are only two input sources to the blower. Both go thru the "Sword"(N2 Final stage unit) see the attached schematic.

Does the blower run correctly with the blower speed control at the high speed detent? If it doesn't then I would suggest that the blower itself or the connections to it are the problem.

If it runs right at high speed but is intermittent or non operational at low and moderate speeds either the replacement part has the same problem that the original had or the main controller has a problem.

Could you describe the problem behavior in more detail and is there a difference in operation between the new and old parts?

bill_rowe2001
08-17-2008, 09:32 PM
The problem is that the blower motor sometimes works and sometimes does not work. When it works, it works on all speeds. In other words, when the motor is operating you have the ability to turn the speed either up or down. Unfortunately, even after the new blower motor sword was installed, the same problem exists. In fact, while at the repair shop and after having paid the shop for the repairs, I went to start the car and the blower motor was not working. The shop will continue to investigate the problem (for a fee I'm sure), but I feel more comfortable investigating the problem myself. An informed customer is hard to screw!

Thank you again, Terry, for responding. Any light you can shed on this problem would be greatly appreciated!

Bill R.

TerryY
08-17-2008, 10:04 PM
If you put it on High when it is misbehaving what happens?

If nothing then check the wiring and the blower motor itself.