'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
You can also measure the resistance across the ground connector and the blower motor connector with the regulator completely removed. If not high resistance, then it is bad.
Just got the new Behr regulator. Measures something like 12 Megaohms between blue & black.Ok, assuming Blue & Black are the connections to check - My regulator measures 6.5ohms. Not very high!