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ACCII auto climate control / blower motor woes

Started by SuitGuy, 17 June 2023, 06:12 PM

SuitGuy

My auto climate control has never worked right. For the longest time, I could have the blower motor run with no issues. Only temperature control was not working. During a road trip this past winter, my fuse burnt up and the blower motor stopped. No biggie, just replace the fuse!
I've been eating through fuses like they're candy. The blower motor will run at different speeds depending on the selected setting (max in DEF, med/slow in BI-LEVEL, high in AUTO-HI, never on AUTO-LO, and off on OFF), so I'm not inclined to believe it's my blower motor creating a dead short. The fuse will generally burn up after about 10 minutes of use or sometimes when the ignition is turned off.
I'm not sure where to begin my diagnosis. My fear is it's a vacuum problem, as are most issues with ACCII. Could this be the AMP misbehaving?
Also, the fuses have not been failing like a normal fuse. They melt before the fuse breaks. I think that is more the fault of cheap Bakelite fuses, but figured I'd mention it here.
Kindly,
SuitGuy
Beige 1980 300SD

rumb

Just guessing but have you looked at the big blower resistor that is behind the firewall?  I think you get to it from the air vent maybe? Not sure.

https://forum.w116.org/test-drive/my-custom-1980-300sd-project-part-2/msg138588/#msg138588

post #97
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

SuitGuy

Thanks for the suggestion rumb, I'll check and see. I have the blower motor without the attached AMP, so I'm not sure if it will have the big resistor you and Squiggle mentioned. I'm beginning to suspect the AMP to be the culprit, given its age and dubious history.
Something I forgot to mention in the initial post--there is a strong electrical smell, not quite burning, that comes from the blower fan when running. I initially thought this was from the oil I used to lubricate the bearings, but it has persisted far too long (3+ months).
Beige 1980 300SD