97 No Ac And No Air Flow
jamesbkimbler
08-13-2006, 04:13 PM
It was the AC control relay. Read on for more specifics.
1997 Pontiac Bonneville SE no super charger;The wifes car.
Over the last few weeks the wife has been complaining to me that there must be a ghost in her car because the A/C comes on and goes off without her touching the controls. Well this past weekend the A/C stoped working all together; i guess the ghost turned the A/C off and split for the summer. I assumed the blower motor had given up the ghost so i purchased and installed a new BM. The broblem was not the BM. So i turned to Automtive Forums for help. The threads relating to this problem all pointed the finger at the HVAC control module located inside the car on the passanger side near a fuse panel. This module was not to blame. Turned out that the AC CONTROL RELAY is where the ghost had resided. There is a fuse panel and a few relays under the hood on the firewall. The Relay was the the third from left; i tracked it down by tracing the purple wire from the blower motor connector. The relay has five pins. Pins 86 & 85 are energized when the air is turned on any setting: AC, Heat or Defrost. When the relay is deenergized (air is off) Pins 30 & 87a are closed. When the relay is energized (air is turned on) Pins 30 & 87a open and Pins 30 & 87 close. It is the Pins 30 & 87 that when this circuit is closed the blower motor runs.
1997 Pontiac Bonneville SE no super charger;The wifes car.
Over the last few weeks the wife has been complaining to me that there must be a ghost in her car because the A/C comes on and goes off without her touching the controls. Well this past weekend the A/C stoped working all together; i guess the ghost turned the A/C off and split for the summer. I assumed the blower motor had given up the ghost so i purchased and installed a new BM. The broblem was not the BM. So i turned to Automtive Forums for help. The threads relating to this problem all pointed the finger at the HVAC control module located inside the car on the passanger side near a fuse panel. This module was not to blame. Turned out that the AC CONTROL RELAY is where the ghost had resided. There is a fuse panel and a few relays under the hood on the firewall. The Relay was the the third from left; i tracked it down by tracing the purple wire from the blower motor connector. The relay has five pins. Pins 86 & 85 are energized when the air is turned on any setting: AC, Heat or Defrost. When the relay is deenergized (air is off) Pins 30 & 87a are closed. When the relay is energized (air is turned on) Pins 30 & 87a open and Pins 30 & 87 close. It is the Pins 30 & 87 that when this circuit is closed the blower motor runs.
markwb
08-16-2006, 08:54 PM
Nice write up. Glad you resolved your problem, they're not all that easy. That is the standard convention with the automotive double pole relays, contacts 30 & 87a are normally closed contacts & contacts 30 & 87 are normally open contacts with relay dropped out. When the relay picks up, contacts 87 & 87a change state, 30 is the common.
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