I have two buicks a 93 and 94 roadmasters both batteries go dead over night or two. On the 93 i had to install a separate relay to bypass heater control it solved problem but is crued. On the 94 I actually can hear the blower fan go on and off with the keys out of the ignition. this must be a fairly common problem or i must be very lucky. Both cars have the automatic heat control. What could it be?
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1994 Buick Roadmaster Question: battery dying over night
Answer #1backyard tech November 27, 2009, 18:21Master
Customer Concern: Automatic system climate control. Blower motor stays running with the key off.
Tests/Procedures: 1. With the key off, check voltage at the Gray/Black wire.
2. If there is no voltage, replace the A/C power module.
Potential Causes: Air Conditiong (A/C) Power Module
Tech Tips: Had 0 volts on the Gray/Black wire.
Replybackyard tech, November 27, 2009, 18:22Master
Customer Concern: Blower motor runs all the time and kills the battery. Has automatic HVAC system.
Tests/Procedures: 1. At the blower control module located underhood in the a/c box center of dash.
2. With a voltmeter backprobed on Gray/Black wire with key off, and blower motor still running, see if that wire is at 0 volts.
Potential Causes: Blower Module
Tech Tips: Normally this wire, with a working blower motor, will vary from about 2 volts on low speed to about 8 volts on high speed. Then when the key is shut off, the wire should go dead and the blower should shut off. If the blower module is bad it is also good to replace the motor as it is what usually takes out the module
Replysonnyhooper, December 01, 2009, 07:25Rookie
replaced the blower motor resistor (module) and seems to work checked voltage at blower purple wire unplugged and it read .004 volts after being replaced before it was at 6-8 volts