Hey Guys/Gals, I'm new to posting but have successfully used this forum to help me sort out both my 328 and 550 in the past...thought I'd give it a try with this odd situation: I have a perplexing issue with my 550...the HVAC blower motor won't shut off. Tried to start the car yesterday, and the battery was weak (cranked for a bit, but didn't have enough juice to start it). After I boosted it with a power-pack, the blower motor won't stop running at full speed. I've tried removing fuses, but it still stays on. No fuse shuts it off. I even unplugged the main power feed to the fusebox and it still keeps running. I disconnected the battery overnight (after I charged it), and as soon as I hook up the terminals, it starts blowing. Clearly there isn't a relay or fuse in the fusebox (as it didn't shut down even after I uplugged the main power feed). Does anyone know if there is a relay elsewhere in the car? Does anyone know how it is wired/powered? Could it be a faulty controller? Thanks, Mike
Others with more knowledge and experience will surely chime in, but to confirm the basics, since ECUs really like their full juice... are you certain that the battery is fully juiced up? Ruben
Thanks Ruben - but the battery is fully charged and the car is operating perfectly. She starts and runs fine...just the blower won't shut off!? Blower runs continually, even with the key out and doors locked. I've played with the HVAC controls (even removed the HVAC control unit) and it still keeps running. It seems to respond to the control unit somewhat, as I can hear the flapper door closing when I put it in recirculation mode. It must get power directly from the battery (through its own fuse?) and have a relay somewhere that is stuck in the open position. Even if the ECU is telling it to run, it should reset after I remove the battery power? I'm guessing at that. I'm confused on why the fuse/relay isn't in the fusebox...
Unfortunately there is nothing I could find in the WSM wiring diagrams showing the power feed to the HVAC fan. In fact I can't even find any reference to the fan motor. This is not the first time I've found the 550 wiring diagrams lacking.
I would suspect a short in the fuse panel. FBB redid his by hand and so far, so good. John Cribb moved the high currency circuits off the board, IIRC.
Here is another thread on the subject: http://www.ferrarichat.com/forum/456-550-575-sponsored-bradan/344701-550-ac-fans-keep-running-ignition-key-off.html Perhaps check relay N by substitution.
Bit of a long shot but maybe the 550 has a similar system. This is a common problem in the 928 world and is usually due to the "resistor pack". https://rennlist.com/forums/928-forum/446437-just-replaced-ac-fan-blower-resistor-pack-only-max-speed.html#post5669080 scroll to the top
Hey Taz and Zedtt - thanks for the suggestions. I don't think the problem is in the fuse panel, as I was able to remove the main power cable to the fusebox, and the blower still keeps running. I removed every fuse and relay, and the blower still keeps running. I found a schematic diagram for the entire HVAC system and it shows a remote relay and an in-line fuse. But it doesn't show the location of the relay. I'm hoping that it is this relay that is stuck. I just can't find it! Anyone out there know where it is located? Thanks again, Mike
I had the same problem on a '99 456M. I had to pull one of the main fuses under the hood to shut it off until I could take the car to the shop. The dealer's service tech said he replaced the "fan resistor block" part number 64280200. May also be called "electro blower regulator" or "solenoid valve regulator." Go figure. It looks like a bunch of aluminum sticks with an electrical connection on one end. It is located on the passenger end of the A/C unit under the dash. The A/C worked correctly when I picked the car up, so apparently that was the problem. The battery had gone dead shortly before this happened, too. I had to jump the battery to get the car started, then I noticed the fan would not stop running. I can't be sure if the running fan discharged the battery, or the battery died for some other reason, but it all happened at the same time. Good luck.
Thanks very much for the info Jerry. Sounds exactly like what happened to me, and interestingly, my 550 uses the exact same part. 64280200 ELECTRO-BLOWER REGULATOR. I was hoping it was going to be a bad relay for $$$ reasons. That regulator is $800 vs. $50 for a relay. Thanks again...Mike
Sounds like it was as I suspected. I have run into this sort of fan control problem on other cars and they basically work on the same principle. When the resistor pack overheats the fan goes to MAX in an attempt to cool it. The reason for overheating varies but it may be as simple as the following link and with a little effort save you $800 bucks... https://rennlist.com/forums/928-forum/615144-so-what-did-you-do-to-your-928-today-397.html#post12526389
Was able to find a used regulator on eBay from a UK company for about $50 delivered. Will try that out when I get it next week. Hope that's the issue... BTW - does anyone know where the main HVAC blower fuse is located? It isn't in the fuse block, and the parts diagram shows it in-line somewhere.
