1991 Buick Park Avenue air fans won't go off

RFINLEN

MEMBER
1991 BUICK PARK AVENUE
6 CYL
FWD
AUTOMATIC
160,000 MILES

Arrived home from work, I had been running A/C.
pushed off on weather control panel, turned off key and had in hand and air fan blowinh air on window and blowing air on feet continued to run.
Only way I could stop was to disconnect battery.
Friend next day said I probably have a "dead short"
in fan unit !
Me, I knowing nothing but care to avoid a 300/400 dollar bill at auto dealer.
thx in advance
roger finlen

1 Reply

ED ARMES

MECHANIC
129 POSTS

You cannot discount that the heater control uni t is bad. However once the key is turned off, no power should be going to the blower control switch.

There are 2 blower relays that could be involved.

One relay draws its power directly from the fuse block
( Fuse #5D-25amp.) This power from this relay goes directly into the heater controls assembly.

The other one takes its power out of the heater control assembly and is directly tied into the blower motor. It is the high speed relay. Does the fan work only on high mode when this happens?

It is possible one or the other of these relsys is stuck on. Other wise you may have 2 wires shorted across each other keeping the system hot.

Far fetched woul be the ignition switch failing and not canceling power to the accessories.