2005 A/C Switch Wiring
11-10-2015, 04:25 PM
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2005 A/C Switch Wiring
Does anybody have a diagram of the actual a/c switch for an AP2? (2005)
I've looked in a friends AP1 FSM (I assume would be close enough to determine what I need), I've checked Mitchell On Demand at work, as well as All Data.
I cannot find one!
I am away from my car and cannot use a DMM to test.
any wiring diagram I can find DOES NOT provide details for the actual a/c switch, just the general a/c system as a whole. I find this extremely odd.
But anyway, what I need to know is:
Does the actual A/C switch itself (HVAC Control switch on the dash) provide a GROUND to the rest of the circuit or POWER to the rest of the circuit? And if it's providing power, is it providing 5v or a full 12v?
Typically most manufacturers will have 12v going straight to the switch and then each selection "completes the circuit".
I've found in the past that some asian vehicles use ground to complete the circuit via the switch.
Please don't answer if you're just guessing, as that doesn't help me. I originally thought these switches provided a ground, but I'm not so sure after looking at the diagrams I can find.
All I can find for sure is that the ECM pin A27 blue/red "detects a/c switch signal" and has around 0v with a/c switch ON, and about 5v with the a/c switch off. Does this suggest the switch provides a ground? Who knows.
From additional research, it seems that A27 goes from A27 at the ECM through the a/c pressure switch (which if pressure is neither too high/low then the switch is closed and continuity is maintained to continue it's path). From the pressure switch, it goes to pin 12 (blue/white) on the Heater Control Panel. Pin 12 on this panel is actually listed as an "input".
Any light you guys can shed on this will be extremely helpful to me. I would like concrete evidence. Thanks in advance!
I've looked in a friends AP1 FSM (I assume would be close enough to determine what I need), I've checked Mitchell On Demand at work, as well as All Data.
I cannot find one!
I am away from my car and cannot use a DMM to test.
any wiring diagram I can find DOES NOT provide details for the actual a/c switch, just the general a/c system as a whole. I find this extremely odd.
But anyway, what I need to know is:
Does the actual A/C switch itself (HVAC Control switch on the dash) provide a GROUND to the rest of the circuit or POWER to the rest of the circuit? And if it's providing power, is it providing 5v or a full 12v?
Typically most manufacturers will have 12v going straight to the switch and then each selection "completes the circuit".
I've found in the past that some asian vehicles use ground to complete the circuit via the switch.
Please don't answer if you're just guessing, as that doesn't help me. I originally thought these switches provided a ground, but I'm not so sure after looking at the diagrams I can find.
All I can find for sure is that the ECM pin A27 blue/red "detects a/c switch signal" and has around 0v with a/c switch ON, and about 5v with the a/c switch off. Does this suggest the switch provides a ground? Who knows.
From additional research, it seems that A27 goes from A27 at the ECM through the a/c pressure switch (which if pressure is neither too high/low then the switch is closed and continuity is maintained to continue it's path). From the pressure switch, it goes to pin 12 (blue/white) on the Heater Control Panel. Pin 12 on this panel is actually listed as an "input".
Any light you guys can shed on this will be extremely helpful to me. I would like concrete evidence. Thanks in advance!
11-11-2015, 03:27 AM
#2
Registered User
Page 21-14 of my 2000-2007 service manual shows the "A/C compressor clutch relay" controlled by a switch labeled ACC that goes to ground.
Got the Service Manual? Same diagram? There are a bunch of pages on troubleshooting the system.
-- Chuck
Got the Service Manual? Same diagram? There are a bunch of pages on troubleshooting the system.
-- Chuck
11-12-2015, 05:35 AM
#3
Hi Jonathan_ed3,
Per my 2000-2006 FSM, the "heater control panel" controls several circuits, switching ground or power or both depending on the circuit: AC compressor clutch relay via the ECM, blower motor transistor, air mix control motor, mode control motor, recirculation control motor, lights, and gauge assembly.
Which circuit are you talking about?
The wiring diagram shows just enough internals of the ECM and the heater control panel for me to see that pin 27 of the ECM has a pullup to 5 V, and the heater control panel switches this pin to ground. In the ECM are shown a couple of transistors, apparently controlled by this signal, that ground the coils for the AC compressor clutch relay (ECM pin A17) and radiator fan relay (pin A20) to turn them on. What is not clear is how these transistors are driven--there must be an inverter in the ECM that is not shown.
Hope this helps.
Wayne
Per my 2000-2006 FSM, the "heater control panel" controls several circuits, switching ground or power or both depending on the circuit: AC compressor clutch relay via the ECM, blower motor transistor, air mix control motor, mode control motor, recirculation control motor, lights, and gauge assembly.
Which circuit are you talking about?
The wiring diagram shows just enough internals of the ECM and the heater control panel for me to see that pin 27 of the ECM has a pullup to 5 V, and the heater control panel switches this pin to ground. In the ECM are shown a couple of transistors, apparently controlled by this signal, that ground the coils for the AC compressor clutch relay (ECM pin A17) and radiator fan relay (pin A20) to turn them on. What is not clear is how these transistors are driven--there must be an inverter in the ECM that is not shown.
Hope this helps.
Wayne
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