Surge709

So I just bought a used 2004 Suburban Z71 and have had a few small issues. The rear vents have no air coming out of them no matter what setting the front controls are set in. Any suggestions as to how to trouble shoot?

Also, might be related, my rear view mirror won't display the temperature or travel direction while the onstar and auto-dimming features are working. Tried to find the fuses for this but no luck. Any suggestions?

Thank you!

Surge709

Any thoughts?

johntaps

If you can hear the fan running but no air, you've got a bad "mode" door motor. If the ac blower motor isn't running, it's either a bad fuse, bad blower motor, or bad blower motor resistor.

Surge709

Any thoughts on how to diagnose? I thought I went through all of the fuses but could be missing some... Does the fact that the compass on the rear view mirror is also out suggest bad wiring/a fuse.

This is a new (used) car for me so could have some demons

in2pro

re-check all the fuses, did the previous owner have any aftermarket items installed/removed, if so check the wiring around those items.
Check the under hood relays also...
Gain access to the rear fan assembly and check for voltage at the fan with the rear AC enabled... if you get voltage then you know the fan is most likely out...if no voltage then an open fuse or broken circuit exists....

Surge709

Thank you.

1) Where is the rear AC fan?
2) Is there such an occurrence that if the freon (or what ever is in the AC system) is low, it will auto-shut off?

in2pro

The rear fan is in the passenger side rear quarter panel.
Low Freon will prevent the compressor from coming on but not the fan...

Surge709

My rear AC blower won't turn on. I have a 2004 suburban with auto rear AC. Here is the strange part: the rear blower is getting ~2.5 volts in the power cable and ~1.3 volts in the black(ground). The resistor has both a 12 volt power and a good ground but the middle wire (input) is reading a very light .05 volts.... That seems wrong.

All of the fuses are fine and the system is turned on to full AC. Any thoughts?

Surge709

No ideas? I am stumped ...

kevinkpk

You need to read one of those to ground. I believe those are the power wires from the resistor block. Put + lead in one, - lead to a good frame ground such as the motor base. I don't know which color wire is high, so you might end up checking all of them for voltage.