SL500 blower motor

[rob300e]

Hey all, I have a 2000 SL500 whose blower motor went out. The indie said the strap broke and let the motor rub on the housing and burn out. I gave him a new motor with squirrel cage etc but the fan works intermittently. He is convinced from his reading online that the regulator is the culprit, but said there are several different to choose from.
There are 2 different choices, I think i bought the Behr motor but he doesn't think the regulator comes separate. Any ideas which regulator to get?
Many thanks in advance