| Re: 84 - Location of the blower relays |
Subject: Re: 84 - Location of the blower relays by rayquayle on 2008/8/31 8:31:33 Quote: when I reviewed the 84 manual, it was clear that if the resistor failed, the fan will run. Not so clear to me. The Relay has two states, energized and de-energized. In the de-energized state, the current flows through the resistor pack. Based on the Blower Switch position, the current goes through one, two or all three resistors, through the NC contacts of the Relay and on to the Blower Motor. This current is only there when the A/C is not in the OFF position and only with the ignition in RUN. So if a resistor were to open you'd lose that speed. If all the resistors opened, you'd lose all speeds except HI. If all the resistors shorted, you'd get HI speed from the Blower in all speed positions, but only with Ignition in RUN and the A/C set to anything but OFF. The Blower won't run at all times (Ignition or A/C OFF) with a Resistor Pack fault. In the energized state, the Blower gets current directly from the Battery through a Fusible Link. The Relay is energized by current through the A/C switch and the Blower Switch. Again current is only there when the Ignition is in RUN and the A/C is in an other than OFF mode. But if the Relay were to have its NO contacts stick closed, current would flow from the Battery through the fusible link, through the Relay's stuck closed NO contacts and on to the Blower Motor at all times. You'd have to disconnect something (Battery or Relay) to get it to stop. Quote: Check both, but I would bet the resistor is toast. They don't last forever!  Sure check both, but with no moving parts the Resistor Pack doesn't fail anywhere near as often as the Relay and when it does, it almost always results in lost non-HI speeds. I'd be very surprised if the Resistor Pack or any resistor within the pack is bad, given the original problem. Now once the Relay is replaced and the Blower Motor is not running at high speed all the time, he may find that one or more low speeds are not working. Then the Resistor Pack needs looking at.Here's the schematic from the '84 manual:  |
