Blower Issues in Auto Hi and Low
 

Hello All-

I am trying to restore the climate control in my 1977 300D. When I bought the car only the defrost worked (I really wished I would have done more homework on how much of a pain climate control issues are). Anyways, I looked at the dreaded servo and found that is was cracked and non functional. I also found that my amplifier looked scorched. I decided to buy the ACCII upgrade from Unwired Tools, along with a new auxiliary water pump (for the heater), totaling about $600.00:eek:. Thankfully, upon installing the digital servo, my vents came to life! Defrost blows very hot and very strong I could almost fly a kite off the vent. Auto Hi and Low temperature settings seems to be working, and I had verified the thumbwheel potentiometer had the minimum resistance range on full hot compared to full cold. Also, when I turn the thumbwheel to hot, the center vents close and the leg vents open, and vice versa on the cold setting. However, I am just not getting the gusto of the blower speed as compared to defrost. I have read posts and literature and it looks like Auto Hi has the ability to give max blower power, as does defrost, however, I probably get half that.

1. I know blower speed is a function of the ambient and in-car temperature settings. If one of these are not working, could it cause the blower to slow down so to speak? If so, can anyone lead me to some posts on how to test?

2. Is it the blower itself? The blower is strong on defrost so it works, but I know the blower is actuated by vacuum. Could a vacuum leak be the culprit? I have not yet tested the vacuum lines in my climate control...from what I hear it is a pain...

3. Could it be bad electrical connections in my climate control console or actuators? The back of my vertical pushbutton assembly has two wires that got hot enough to melt the plastic, possibly from a stuck servo. Maybe this needs to be replaced?

Sorry for the long post I just want to try and narrow my search before I blindly start looking for problems. I want a good working climate control for my car. I wanted to get the heat, vents, and AC all working properly. I got the heat now, the vents seem to work well, and it is only 4 months til June so I better get the AC and blower working by then!

Thanks :D

Peter
1977 300D 112K

I believe the vacuum control switch on the the blower is strictly on/off. Not enough vacuum and blower won't work. I don't think it could cause less than full blow.
I'd have to carry out a test to be sure, but my recollection is that the HI setting is not as high as defrost. (I may be wrong).

I think you are right on the vacuum being strictly on/off. Any other thoughts on this? In some of the literature I have read, I think the heat on auto-hi has a setting that is as fast as defrost. It is nowhere near close to that. Any other thoughts on this one?