Question: Runaway blower motor

[Bob Bewalda]

My 92 has decided to run the blower motor on high speed, with the ignition on or off ! I have to unplug the connection to the blower motor so the battery doesn't run down.
Any ideas ?;help

 

[gbrtng]

Manual or automatic air?

 

[Bob Bewalda]

Automatic Air/Heat

 

[gbrtng]

Looking at the 91 FSM, section 8A-66, there are several components that could have failed.
The most likely part is the blower control module which is on the top of the evaporator housing in the engine compartment, but it could also be the heater and AC programmer or the control head in the dash. The FSM has a diagnostic tree which could help you find the problem. Suggest you get an FSM for your 92 first.

 

[Bob Bewalda]

Thanks, I'll have to see if there are some photo's to show the location, as the wiring is part of the harness assembly, and hard to follow.

 

[vetteoz]

blower control module which is on the top of the evaporator housing in the engine compartment,

Common problem
Most likely Blower Control Module is faulty
Is basically a elec relay controlled by the HVAC head unit so when it fails it supplies power direct from batt to fan regardless of key position .
If the head unit itself was faulty blower would not run key OFF ; because there is no power to the head unit for it to operate the BCM

Also check the fuse in the holder mounted to the blower motor .If the fuse opens, the Blower can stay powered up,