Hey guys.Hopefully you can help.The heater-a/c on my 89 300e 3.0l doesent have as much output(flow) as it did.The temp is ok but not much air volume.It also doesent seem to change much from low speed to high speed.
Any input would be appreciated.Thanks.

Blower speed regultaor (voltage regulator) on the vehicle is a very common, I would even say most common, fault in the climate control system.
It is a relatively easy repair as long as you have basic auto knowledge and experience - If I remember right those regulators are freaking expensive. Over 200 bucks.

Do you know where on the vehicle it is & how to test it?Thanks

It's been a while.

It's under the wiper assembly with the blower motor. I don't know the resistance spec sorry. Search on this site for DIY manual -it's such a common repair there should be one.

Before looking to the blower motor , I would check the 3 prong plug coming through the firewall by the booster
This is power and regulator trigger voltage from the Control panel to vary the speeds . The red and blk are 12v. but the yellow should go from 2 to 7 volts for the trigger voltage to the regulator... if you do not have this , your problem is not the blower or regulator, but rather the control variable voltage feed to the regulator[ variable trigger voltage...]

Thanks arthur.Tomorrow ill check that.When should I get my 2-7 volts at the yellow wire?Is it when I change fan speeds?Also I am guessing I should have it plugged in when I test it??Why do they use a "trigger voltage along with a voltage reg.Just wondering,.Thanks again.

It is under the hood. Directly beneath the blower casing/housing. It can't been seen without removing the blower motor.

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1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k