99 Suburban Rear Air Issues... I'm Losing My Mind

[Bozz]

Hello GMTers. I'm going nutz tracking this rear A/C issue. 99 Burban. Rear blower quit several months back. Off and on I've looked at it from fuse box (interior), under hood fuse/relays, etc. I have replaced the resistors (front behind glovebox) as well as the resistor in the rear blower location. I most recently found a NOS blower motor and replaced it. I said I wasn't going to do this anymore but I've started replacing parts hoping for the best.

Concerning wiring, I have checked the orange wire at the driver's side kick panel and it was not burned as many report BUT I went ahead and bypassed that connector and spliced the orange wires together.

As of now...I can turn key on, turn Front Panel Controls on (in dash), turn Front roof passenger control to REAR CONTROLS, turn passenger controls in roof behind front seats on and ad I rotate the fan speed control knob to all 3 speeds, I can hear the 3 rear relays beside the rear blower motor faintly "tick". No blower in the rear at any time in any position whether controlled front front or passenger.

Like I said it quit several months back and the front blows fine. But one day it just quit...no burning magic smoke sign or smells.

If someone who has been through this ( I know many have, I've read a lot of posts) and had a few minutes can walk me through this. I found another "resistor" up under the headliner today...at least Rock Auto calls it a resistor. I pulled it, inspected for cold solder joints, etc and it looks good but ?

What am I missing? I'm to the point of wiring the rear blower to a fused switch up front and control it from there but I discovered that would not allow for floor/face control. So to get it right I've got to fix it right. I have all controls hanging and accessible so I can test what I am advised to test to determine this gremlin. I have a test light and multimeter at the ready.

Thanks in advance for reading and to those that may could wire one of these blindfolded, I anxiously await your reply.

Bozz in Kentucky

 

[SUBURBAN5]

So the rear is not receiving power at all?

 

[Bozz]

Well... like I said, I can hear faint ticks from rear relays as I operate the fan speed controls from the rear passenger position. But at the rear blower...no there is no power.

 

[GoToGuy]

Relays are remote switches basically. Like wall switch clicks but lights don't work if there's no power. Ok. From your description, You hear the relay click, it should send power to what needs it. When you switch fan on. ( click!) relay should have one hot to energize relay, and one hot out to power fan. You can have a relay function normally, but is there power for it to send out. Test every section for power continuity. And dont forget the grounds. Known good fan tested checked. Good power voltage all the way to fan plug, grounds? This isn't impossible, power is alot like water, needs somewhere to go, and path of least resistance.

 

[Bozz]

I have not checked those relays. I'll check them. I assumed the click was evidence that they are trying to do their job. In all my years I have never had to replace a faulty relay...guess I've just been lucky.