Quote:
Originally Posted by jgl1
1997 SL 600 (U.S. spec, 129.076)... climate control no longer responding to some commands... request for A/C results in compressor clutch engaging, blower speed is adjustable, as is temperature... but air no longer comes from the center or side dash vents as the vent flaps do not open.
The push button control unit (PBCU) is properly version coded and no fault codes are stored. With use of a M-B HHT in activation mode, vent flap functionality returns.
A fault code check of the instrument cluster reveals one stored fault: B1755, K2 communication, IC to PBCU (N22).
Continuity check of the K1 and K2 CAN lines between the PBCU (N22) and the instrument cluster reveals the lines are intact.
Is it safe to assume that the PBCU is faulty and warrants replacement since the heater box air flap elements are functional when the HHT is connected in activation mode?
Thanks.
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Jg........................
90% of vent problems on these R129's-especially when no center vents are not working. The vacuum distribution block has a leak. The block has this metal 1/8"-3/16" bearing as a plug when it is manufactured(it is visable). The bearing is near the screw hole where it attaches to the inside of the engine area-Well..... The heat from the engine. Heatsinks on the bolt which causes the vacuum distribution to split open right from the bearing. Check this out on post 29:
Just bought a 93 SL500 - Mercedes-Benz Forum
Try that before a replacement climate control..
All the best,
Martin