I know there have been a lot of threads relating to A/C operation & fan-related issues. But a search of The Forum shows threads posted everywhere. So I chose to post a new thread under the Interior Section for my A/C fan issue. I apologize in advance to anyone that I upset.

Anyway, yesterday Roberta & I drove up to a nearby winery and enjoyed a nice lunch & bottle of wine. The A/C seemed to work fine, but I continue to have intermittent fan operation. On the way home, the fan stopped working at all. If I turned off the A/C, reset the fan to OFF position, waited a few minutes, then turned the fan back on, ventilation worked. But only as ventilation. With the A/C ON, the fan won't run continuously. I still feel cold air out the vents, but it's only natural ventilation since the fan won't run continuously. Needless to say it's still hot here in SC and this HVAC fan issue is starting to get on my nerves.

I've replaced the blower resistor & cabin filter plus cleaned out the blower of debris falling in from the blocked drain under the windshield cowling. Car still has the original factory battery. Feedback on Forum says it could be the battery (5 years old) due to quirkiness of XFire controls. Some say it's the HVAC Control Module in the dash. I remember one thread that said it could be worn motor brushes.

Not interested in changing parts, which is all a dealer repair center would do. Looking for some logical checks I can perform to pinpoint the A/C fan problem.

Thanks,

 

here is the problem.

https://www.crossfireforum.org/forum...AC+fan+working

here is how to fix it


https://www.crossfireforum.org/forum...where-get.html

Mine quit a few days ago . so i did a search found the above .Anyway after reading the above I came to the conclusion that my resistor was bad,, so I called the dealer, the Park was well over $400,, so I call the Mercedes dealer, the part was just barely under $400, so I looked online for 2004 : MERCEDES-BENZ : SLK320 : 3.2L V6 : Heat & Air Conditioning
and I found it for 60 or $70, underneath the glovebox i removed first panel with two screws then I removed a plastic cover that covered the blower to the screws out that hold resistor,,note ,, leave the factory red wire there the one they come the resistor is not long enough. Put two wires in, two screws put the resistor back in,Turn everything on to test it, replacement panels, 20 min. later my AC work great,


Oh, I did find water and leaves in their so this is the cause of the Resistor going bad, on these car we need to figure out a way to close off that area so the leaves and water cannot enter there,, I know that it's the vent system but we need something like an intake so that the air can come back and enter the car and that no water or leaves can enter ,and close off under the windshield completely sealed it, I am working on that.
in one of the links there is a pic of the resistor,, and the one who is what you can buy it,, here is where i got mine http://www.google.com/url?sa=t&rct=j...lkZxTQ&cad=rja

I know you said you just change the resistor, is it possible you use the red lead and it came off because it's too short mine actually came off the test because is too short when the blower came on the blowers on rockers and it moves sometime, if I were you I would change the resistor again just to be sure because that's exactly what it sounds like, good luck Jim

 

The fan will not work at times when there is trouble with the AC system, it is a safety feature. Likewise the AC will not work when there is trouble with the fan to prevent freeze up of the coil in the system. I am at a loss on the HVAC side of things.

Does the fan work when you use the heater? If so the problem may lie in the AC system.
You changed the resistor last year, did you change it again?

 

Another thing to look for: It is not uncommon for the electrical connector at the resistor to be corroded or melted when the resistor is found to be bad. Many resistors go bad due to heat and will also melt the connector. Recheck the connector for any damage, look carefully at the contacts/pins for a good connection. Most manufacturers have replacement connectors with pig tails available for purchase, maybe even aftermarket.

James

 

My vote is the HVAC control head.

 

Fan works fine with heat. Leads me to believe the blower motor is okay. Blower motor resistor was changed out last year. I have another resistor, but haven't installed it yet.

 

Since the blower motor operates fine in heating mode, I don't suspect any issues with the wiring connections. But worth checking next weekend. Used the old RED wire since the aftermarket RED one was too short.