HVAC FAN is draining Battery with Ign. key off, Why?

50

Asked by Jul 23, 2013 at 06:42 PM about the 1992 Cadillac Eldorado Coupe FWD

Question type: Maintenance & Repair

HVAC keeps running after engine is stopped and Ignition is turned off and AC is
switched off.

4 Answers

80,285

Sounds like a bad blower motor relay or programmer. HTH. -Jim

50

Thanks Jim, It was the fan relay unit, next to fan motor on firewall, and the fan motor was shot. Replaced both, all is fine. 1st TankerSki

1 people found this helpful.
80,285

Very glad to hear that. Thanks for letting us know. -Jim

Paid an online tech to give me the answer in the manual, my stupidity. Thought he might have the answer to an issue not in the manual. My heater motor, 99 Eldorado, would not shut off even with the control module disconnected and the key off. Turned out that the 5 bolt motor has logic built into the motor and it was shorting out causing the motor to cycle up and down, but never shutting off. The motor is always hot and the control module excites the field to regulate function. An easy check to determine if your motor is the problem is to first check that you have full voltage to the red wire. Then check the center wire to ground with a multi meter. If it starts out around 10 volts and runs up and then back down you have a bad motor. This is done with the connector attached to the motor. To be absolutely certain disconnect the connector from the motor and then check for voltage from the center wire to ground. You should have none with the key off. If the above conditions are met you need a new 5 bolt motor. The three bolt units do not work the same. You need a motor and a lot of patience. They are not a lot of fun to replace. Also lots of luck finding a 5 bolt motor. They don't make them. Four Seasons shows a 5 bolt pattern on their 35121 motor, but when it arrives it only has three and will not replace the 5 bolt unit.

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