[MBZ] Blower control: How should it work?
We're talking about an '85 300D, California model. A few days ago, I noticed that the blower was working intermittently, and mostly not at all. So, I removed it, cleaned it, removed and resoldered its amp, and put it back together. Now it works well enough that I have heat and defrost and maybe it is working as it should be. I really never paid all that much attention to it before and the manual is not so detailed as the convoluted mind of Benz's engineers. Now, the trouble is, I don't know whether what I am observing is correct operation or an anomoly. On defrost and high, the blower starts immediately, which is what I would expect. On low, automatic, and with the heat on any setting other than defrost, there is a delay between my pushing the button and the fan coming on. This delay, which seems quite regular, really confused my diagnostics. Does anyone among you know the logic behind the blower motor controls? Phil '85 300D, California style '84 300D, Euro model and blessedly simple ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Blower control: How should it work?
Typically the blower will come on at the lowest speed only except on defrost of if you have the high speed button pushed. It will then adjust to the correct speed for the required conditioning, usually after 10 or 15 seconds. I think this is supposed to do two things -- prevent a blast of icy cold air in the winter and to clear the damp air in the heater box before it all ends up on the inside of the windows as condensation. I know that on the W124 there is just such a delay, but that's a different system. Also, it will only run on lowest speed until the heater core warms up, and on my current 300D that's a mile or so. Peter On Nov 7, 2008, at 6:30 PM, Phil Andrus wrote: We're talking about an '85 300D, California model. A few days ago, I noticed that the blower was working intermittently, and mostly not at all. So, I removed it, cleaned it, removed and resoldered its amp, and put it back together. Now it works well enough that I have heat and defrost and maybe it is working as it should be. I really never paid all that much attention to it before and the manual is not so detailed as the convoluted mind of Benz's engineers. Now, the trouble is, I don't know whether what I am observing is correct operation or an anomoly. On defrost and high, the blower starts immediately, which is what I would expect. On low, automatic, and with the heat on any setting other than defrost, there is a delay between my pushing the button and the fan coming on. This delay, which seems quite regular, really confused my diagnostics. Does anyone among you know the logic behind the blower motor controls? Phil '85 300D, California style '84 300D, Euro model and blessedly simple ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Blower control: How should it work?
For settings other than defrost and high, a temp sensor determines how much air is needed to satisfy what you're asking for, then it turns the fan on very low or higher depending on how close the temp in the car is to what you're asking for. Usually, if there's a wide difference between temp in the car and what you're calling for, the fan will run faster; as the difference gets smaller, the fan slows down. I seldom change the settings in my 124 and 126; with the fan in AUTO, and the temp setting where I want it, the fan just comes on slow or fast as the system needs it. Wife, however, can't seem to understand, though she's been driving MB's for 29 years, wants the fan blowing the instant she releases the key after starting, so she fiddles with the AC controls trying to get the fan on immediately. I've been telling her, Leave it alone; it'll come on after it has determined how much is needed. If starting cold in winter, for example, fan will not start 'til some heat from engine coolant is available. Wilton - Original Message - From: Phil Andrus [EMAIL PROTECTED] To: mercedes@okiebenz.com Sent: Friday, November 07, 2008 7:30 PM Subject: [MBZ] Blower control: How should it work? We're talking about an '85 300D, California model. A few days ago, I noticed that the blower was working intermittently, and mostly not at all. So, I removed it, cleaned it, removed and resoldered its amp, and put it back together. Now it works well enough that I have heat and defrost and maybe it is working as it should be. I really never paid all that much attention to it before and the manual is not so detailed as the convoluted mind of Benz's engineers. Now, the trouble is, I don't know whether what I am observing is correct operation or an anomoly. On defrost and high, the blower starts immediately, which is what I would expect. On low, automatic, and with the heat on any setting other than defrost, there is a delay between my pushing the button and the fan coming on. This delay, which seems quite regular, really confused my diagnostics. Does anyone among you know the logic behind the blower motor controls? Phil '85 300D, California style '84 300D, Euro model and blessedly simple ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] Blower control: How should it work?
operation or an anomoly. On defrost and high, the blower starts immediately, which is what I would expect. On low, automatic, and with the heat on any setting other than defrost, there is a delay between my pushing the button and the fan coming on. This delay, which seems quite regular, really confused my diagnostics. Exactly right. The system reacts gradually, so as to operate somewhat below the threshold of perception. Except in Defrost modes. It's intended to be set and forget, and to never blow a blast of cold air at you when what you want is warm. I love the system when it's working correctly. -- Jim ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
