The AC/heater fan speed does not increase when it is set past the 4th bar (out of 7). The fan speed remains the same at levels 4, 5, 6 &7. I also hear a high pitch/squeaky whistle noise from the fan when it is at level 4.

Any ideas as to the cause of this problem and how to fix it.

Thanks in advance.

Other than electrical control problems (usually blower regulator), the volume of air is significantly reduced and accompanying hissing noises can often occur due to lack of maintenance of the cabin filters.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Are you referring to the filters behind the glove box? Are there any other filters?

Those are the ones. If you have a charcoal filter you also will get better airflow if you turn it off.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I replaced the filters behind the glove box and the noise is gone. But the fan is still maxed out at level 4.

How can I check the blower regulator to see if that is the problem? Is it easy to replace?

Also, how can I tell if there is a charcoal filter in my car? Where is it located?

I found & purchased a blower with regulator on e-bay for $250. It arrived today and I replaced it myself in less than 1 hour. Everything works perfectly now just in time for the anticipated hot summer.

Thanks for your advice.