problem with ac/fan
 

Last three road trips i've made the AC fan shuts way down after about 2 1/2 hours of driving (ambient temp outside has remained the same- hot). Even when I punch MAX it doesn't change much- you can hear lots of fan noise, but not much air coming out any of the AC vents- body, dash, floor. (MAX setting when I first start the car is fine, cools down quickly, lots of air blowing through the vents). For the first couple of hours everything is fine- no changes made to any of the settings i-drive or otherwise. Just a diminution of air coming out. Car is a 2008 4.8, about 16,000 miles. Anybody experience anything similar? Thanks. :dunno:

typical bmw... end stage resistor

Theres a SIB about blowing hot air after a drive rather than shutting done .. may be related .. it's to do with warm air flowing past a sensor or something.. will try and find it...

Do you have rear A/C?

I know with mine, if the fan in the rear is turned up, the air flow to the front is greatly reduced.

yes, but it wasn't blowing out of there either.

update on ac/fan problem
 

Took to dealer for repair- said it was the final stage resistor. Brought "repaired" car around for me to drive home, I get in, and a loud low rumblng noise is coming from the fan (not there before). Tech said the short in the resistor must have caused the fan blower get out of balance. Now they want to replace the blower. Not in stock, will be in early next week. Will try again.

Sounds to me like an assembly screw-up and the squirrelcage is rubbing. Maybe they dropped the blower assembly. In any case, a new fan and reassembly should fix it.

lol did i not call it? end stage resister... very common amongst bmw

You are right- but you should have warned me about them screwing up the blower! (just kidding)

actually the blower is common too... so you do have a point ;) in the last 10 years of owning bmw's i've had 4 end stage resister go bad and 2 blower replacement AND a heat exchanger replacement. its just something that bmw can't ever get right, their HVAC system.

in the summer of 2002, the end stage resister was on back order for like 4 week, it was totally f'd up. I ended up writing BMW NA calling my ultimate driving machine an ultimate paper weight because it was useless in the 90-100 degree summer we had. after the letter the part miraculously showed up.

-john

Sorta makes me wonder if I'm doing the right thing replacing my 200,000 mile 1992 Ford Explorer with a new X5 diesel -- my Explorer is still working fine with it's original blower and blower resistor (though I must say it is not unusual for the blower resistors to go bad in almost any vehicle... it's a not uncommon failure on Ford Focuses, and my Toyota had one go bad).

But four resistors in ten years sounds more like a maintenance item than a repair. Maybe BMW needs to add "Replace Final Stage Resistor" to it's 15,000 mile oil change service!

no... smart money is on a used acura mdx or a lexus rx 400h... living with bmw over engineered solutions that end up breaking is sorta the cost of doing business with bmw ;)

You're right, but I must admit my 2004 Z4 hasn't had too many problems. Just a new CD player, new windshield to fix bubbling rain sensor, new set of coils as a service action, and another thing or two... all under warranty. Oh, and a cracked and leaking air filter to Throttle body hose, which I replaced myself for $50. Of course, it only has 30,000 miles on it.

My Ford Focus has 57,000 miles on it and had one problem -- a notchy throttle body replaced under warranty.

Overall my luck has been pretty good except for one notable exception:

1984 325- nothing
1992 325i- only had to replace a window lift motor
2000 M Roadster- nothing
2002 X5 4.4- nothing
2006 650i convert.- entire top assembly replaced; entire CPU replaced
2008 X5 4.8- two AC vent tabs replaced; torn leather as result of fixing vent tabs; end stage resistor; blower

Can anyone point me to final stage replacement instructions? I see the E53 instructions and videos all over, but I can't find anything for the E70. Thanks!