5-Series (E12,E28, E34, E39, E60)Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)
My wife said the heater would sometimes go off by itself then come back on. Until yesterday it did not affect the battery voltage.
Now a faint buzzing sound behind radio with key off drains battery down to 7 volts. Recharge to 12.5 volts and in 10 minutes back to 7 volts Battery is only 3 months old,
Taking out #9 fuse in the glove box stops the buzzing. I see #9 supplies the Heat/AC control Module circuit. Before I do any further dismantling I thought I would ask is there a specific motor or other electrical device more prone to failure.
The faint buzzing sound occurs ignition on or off. It sounds like its coming from directly behind the center LCD display.
With ignition on I ran the air volume switch all the way both directions.
Although the red bars showed increases and decreases the buzz sound seemed to stay the same. I don't think the blower is working. The schematic
shows output from the control module going to " blower relay, blower , blower motor output stage" I'll try to check that direction.
I seldom drive the car so I am unfamiliar with the proper sound of a BMW blower motor going through it's speed range.
Maybe tomorrow I'll pull the radio to better access the IHKA control panel module since the service manual says it's there and best I can tell so is the buzz. Sound seems more electronic than mechanical.
Well I pulled the radio and CD player. Then slid the climate control
unit out. The buzz was in that unit.
Next day. In reading up on blower motors, relays and FSU on the web I see many people with problems resolved by replacing the FSU. I ordered one but while waiting thought if I put the control unit back in then take out the FSU I might find the FSU was causing the control buzz.
The buzz was gone when I put the control back in prior to taking out the FSU.
Typical of electrical problems.
Took out the FSU and will install the new one as soon as it arrives.
Hope that does it.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.