FYI: 12V switched power sources
- Thread starter spressomon
- Start date
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Dusting off this old thread so someone can school me on this.
Background: I need to repair some of my HVAC buttons, so while researching that I've became interested in this odd "unsued" button situation on our 100-series. My truck has rear roof controls but no controls in back of center console. My understanding of my HVAC system was that the main front controls handled all the heat functions, while the rear AC was controlled by the rear roof controls, IF the rear system was on via the master "(fan) REAR" button.
I've found these related threads but still don't quite understand a couple things.
The A/C portion I can follow and it matches my truck, and my understanding, that the "(fan) REAR" button is the master on/off for the Rear AC:
But it also has this page:
My truck has a blank on the back of the center console, instead of the heater controls shown, and a blank button cover on the dash, instead of the REAR HEAT HI/LOW button. However, as noted in the other threads, when I remove the button cover, there is a "working" button and light. The button light follows the OFF/ON/ON function as noted. I also hear what sounds like a relay click somewhere on the left-hand side of the dash area.
Here's the EWD for the Rear Heat w/o Rear AC for reference. The rear heater switch is shown lower right, along with two different heater relays:
However, the "Rear Air Conditioning" page from the EWD shows the "Rear A/C Control Switch" (i.e. the rear roof controls) controlling the Rear Heater Relay, Rear Heather Power Transistor, and Rear Heater Blower Motor.
Further, the system outline says that rear roof control does in fact control the rear heater blower motor:
So, my two initial questions are:
Background: I need to repair some of my HVAC buttons, so while researching that I've became interested in this odd "unsued" button situation on our 100-series. My truck has rear roof controls but no controls in back of center console. My understanding of my HVAC system was that the main front controls handled all the heat functions, while the rear AC was controlled by the rear roof controls, IF the rear system was on via the master "(fan) REAR" button.
I've found these related threads but still don't quite understand a couple things.
- What is this blank below the head unit?
- Rear heater?
- Rear heater controls?! Am I missing something?
- New 100 series owner! Rear heat question
The A/C portion I can follow and it matches my truck, and my understanding, that the "(fan) REAR" button is the master on/off for the Rear AC:
But it also has this page:
My truck has a blank on the back of the center console, instead of the heater controls shown, and a blank button cover on the dash, instead of the REAR HEAT HI/LOW button. However, as noted in the other threads, when I remove the button cover, there is a "working" button and light. The button light follows the OFF/ON/ON function as noted. I also hear what sounds like a relay click somewhere on the left-hand side of the dash area.
Here's the EWD for the Rear Heat w/o Rear AC for reference. The rear heater switch is shown lower right, along with two different heater relays:
However, the "Rear Air Conditioning" page from the EWD shows the "Rear A/C Control Switch" (i.e. the rear roof controls) controlling the Rear Heater Relay, Rear Heather Power Transistor, and Rear Heater Blower Motor.
Further, the system outline says that rear roof control does in fact control the rear heater blower motor:
So, my two initial questions are:
- Is the rear heater fan motor only controlled by that rear roof switch?
- Does the uncovered rear heat HI/LO override or otherwise affect the operation of the rear heater blower fan?
- If the answer to #2 is no, then what relay is clicking when I push that button and where is it located?