2006 EB Rear HVAC Inoperable / Fuse, Relay, Resistor Good

[2006Overlander]

Good evening!

I currently am battling no voltage to the rear auxiliary fan blower motor plug. All fuses and relays are intact leading up to the blower motor. All relays and fuses are intact inside of the forward pax side fuse box. I have checked the relay that is hidden in the Auxiliary Relay Box #2 located above and forward of the right rear pax wheel. I have power in there from pin #86 to #30 on the auxiliary fan blower relay.

The other relay ( I could be goofing the names up) that is located on the physical rear unit which is another blower relay? Is found to be intact and operable.

I can hear both actuators working as I have checked them being operable by changing the position of the vent and the temperature. As well as them being brand new. Didn’t know if that had anything tied into the blower system itself.

Still no Power to the plug itself. I have found on that plug that the wiring going into the plug had a small nick exposing the wiring. As well as the same on the relay just forward of the fan motor plug. Below pictures will be attached of each.

I have powered the new fan by directly hooking it up to 12v power and it works so it isn’t a crap fan.

Is there anywhere else in the vehicle I can inspect/test for anything related to the rear hvac ? Previous owner did mention that the rear fan was intermittent. Now it’s just not working.

I am currently standing in front of a wall that I can’t hop over with this issue. Any service manuals or wiring diagrams will be appreciated. As well as any and all help is appreciated.

 

[whtbronco]

Have you checked the center console rear hvac controls? I'm assuming you have them.

Here's some 2004 diagrams, likely the same for the 2006.

 

[2006Overlander]

The center console controls for the temp and location just fine. I can hear the actuators running. When I select the location of air and the temperature.
What exactly am I checking ? Am I checking continuity somewhere? These schematics seem to be incomplete or not really showing where the locations of these plugs/connectors are

 

[whtbronco]

Yeah those are the electrical diagrams, they basically show the circuits between the switches and the controlled device like the fan. I thought that's what you asked for. They note the connectors, but don't show them.

You can get a subscription to AllDataDIY and have access to all the diagrams you need/want along with instructions on how to remove/install/troubleshoot based on the original vehicle service manuals. Just a thought, it's what I have for my vehicles and to me it's invaluable.

Is this what you were looking for:

 

[2006Overlander]

Yes. Now how would I check the continuity between the resistor pins? I saw another post but I lost it

But I am now noting with chasing power I noticed the rear fan only gets power when the front AC is on. Is that normal op?

 

[whtbronco]

Yes. Now how would I check the continuity between the resistor pins? I saw another post but I lost it

I don't know how off hand to check continuity between the resistor pins. This should help:

https://www.carparts.com/blog/how-to-test-a-blower-motor-resistor/

The diagram below might help:


I can't tell exactly where this connector is, but maybe you'll come across it and this would help:




It is normal that the rear HVAC gets no power, no signal unless the front HVAC is on. The rear fan should get power with any setting that turns the front fan on.

 

[whtbronco]

Here's another:

 

[2006Overlander]

Thank you once again for the replies and continuous help. Now another boneheaded question as I am so flustered with this whole thing, when I'm pinning said connectors for the controls, I am going to have the truck running correct?

So with the Rear HVAC only having power with the front HVAC on as normal power would I be still getting a signal to Pin 2 on the Rear blower plug itself? I'll go ahead and check the resistor once more. Upon visual inspection it appears fine and not burnt.

I will report back with my findings and readings upon each pin of the resistor and the controls, if they are out of tolerance, I suspect it should be replaced.

 

[2006Overlander]

In my mind, if I'm getting power to the plug itself and the fan still not turning, I believe it could be a signal issue. But with the signal issue assumption, I am still getting power when selecting the fan speed on both controls.

At first I assumed the EATC being inoperable due to the first assumption of the rear not receiving power unless the Front HVAC was on, but with that being deemed normal op, I am lost once again.

Am I missing somewhere to diagnose? Should I be checking any where else?

So far as an update I have checked
All fuses related to the HVAC (Front & Rear)
All relays related to the HVAC (Front & Rear)
Connectors and plugs (No noticeable damage or burning/charring)
Fan operable (tested with straight 12v power)
Actuators operable (brand new and observed that they indeed turn and move)
Controls work (Turn actuators, plug receives power etc)

Like said in previous reply (#8), I will report back with resistance readings on said pins.

 

[whtbronco]

You should not need the truck running, but the ignition will certainly need to be set to on/run. That way you can turn on the front HVAC. You have verified the rear fan works and that you have power at the rear resistor. Sounds like you are debating if it's a signal issue or resistor issue and I agree with that. If you have rear HVAC controls in the back of the center console then you have 2 switches for the rear system. If the front switch is not set to position 1 then the rear switch will not function. I'm just thinking through the keyboard, you may already know all this.

I went and re-read your last 2 posts, I already have the above so I leave it, but it may be worthless at this point.

With everything you've tested and the results you have identified I'd say it has to be the resistor.

You can get a replacement Standard Motor Products brand rear resistor for $13 delivered. I would probably just swap it and then get back to the electrical testing if that doesn't resolve it. Testing the electrical system on modern vehicles always seems to drive me mad.