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Ask Derek Werner Your Own Question
Derek Werner
Derek Werner, Cadillac Technician
Category: Cadillac
Satisfied Customers: 135
Experience:  ASE Master Technician, L1 Advanced Level Specialist
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I have only hot aire oming out of rear air ducts

Customer Question

i have only hot aire oming out of rear air ducts
Submitted: 9 months ago.
Category: Cadillac
Expert:  Derek Werner replied 9 months ago.

Hello and thanks for using JustAnswer!

I am Derek, an ASE master technician and will be happy to assist you with your Cadillac Escalade.

Are you referring to the rear air-conditioning system?

Customer: replied 9 months ago.
i have replaced both recir and temp actuators and the control module/resistor to no effect. i did relearn the system after replacing each part. i noticed the temp actuator doesn;t spin...even when being hand held...not in the housing mount when turning the temp.
Expert:  Derek Werner replied 9 months ago.

Does the temp switch to cold when you manually turn the temp door by hand? Sometimes the temp door will break internal in the rear A/C unit.

And for the actuator not moving. I am sorry to say if you replaced the module it will need to be reprogrammed at a dealership. Or a shop that can program GM vehicles. It will not work until the module gets programmed to the vehicle and the actuators relearned.

Expert:  Derek Werner replied 9 months ago.

When manually moving the temperature door you should be able to feel the door stop when turned back and forth. If it spins freely the door has likely broken.

Customer: replied 9 months ago.
i have not taken the entire shroud off. so if you are saying i have to do that to get to the doors no i haven't. unless you are saying i can stick a pencil or something in the hole and try to turn it manually.
i read that all i have to do is pull the fuse for the HVAC rear wait 30 secs put it back and turn on vehicle to reprogram. when i do that i can see both actuators moving back and forth. one just doesn't move with dial for temp.
Customer: replied 9 months ago.
it is true that when i turn the temp cold to hot that actuator should rotate correct? the fact that it is not is due to what? knowing i have replaced the resistor/ac module....only thing it could be is the actuator itself or the doors inside
Expert:  Derek Werner replied 9 months ago.

What I do to turn the temp door, is just remove the screws from the actuator and turn the actuator by hand to move the temp door. You will feel the door hit the stops turning back and forth.

You are correct about pulling the rear HVAC fuse for 30 seconds, turn on the vehicle and wait 2 minutes without moving the HVAC controls. This will recalibrate the actuators.

This is not considered reprogramming. The software inside the rear HVAC controller needs to be reflashed with a laptop software and requires special tools.

Expert:  Derek Werner replied 9 months ago.

Turning the temp door one direction will place the system into full cold and the other direction will blow hot air.

Expert:  Derek Werner replied 9 months ago.

You are correct the temp door actuator should move when turning the tempeture dial.

But the problem is it will not work until the software is reflashed for the rear HVAC module. This is due to the fact that you have replaced the module.

Customer: replied 9 months ago.
well i put the old module back in since the new one didn't do anything
Expert:  Derek Werner replied 9 months ago.

The old module could still be the problem.

Do you have a scan tool that can communicate with the rear HVAC system?

Customer: replied 9 months ago.
no. i have taken apart the temp actuator. there is no way i can move those gears manually. so i took the post out from the unit and am trying it in the housing now
Expert:  Derek Werner replied 9 months ago.

Ok, so one very important thing that needs to be checked before installing the HVAC actuators is checking they have not moved out of the proper range.

If you look at the back of the actuator do you notice the 2 lines and the 1 notch?

Expert:  Derek Werner replied 9 months ago.

ok sounds great let me know what you find. If the door is broken, it will set a fault code and always blow hot or cold air. and this will cause the actuator not to move.

Customer: replied 9 months ago.
i see three lines at the top and one at bottom
Customer: replied 9 months ago.
ok doing manually it got hot and cold
Customer: replied 9 months ago.
the notch on the knob i at the right most line on the actuator
Expert:  Derek Werner replied 9 months ago.

ok great that is good news that the door is not broken internally inside the heater box unit.

before the actuator is installed move the blend door by hand to the middle position.

Then you will need to put the actuator back together with the notch on the knob in the middle of the 2 lines at the top of the actuator. If that notch moves outside of those 2 lines it will set a fault code and not work correctly.

Expert:  Derek Werner replied 9 months ago.

After reinstalling the actuators in the correct position, try re calibrating the system with the old module. If there are no other problems the system should operate normally.

Customer: replied 9 months ago.
all put back together...doing the relearn now
Expert:  Derek Werner replied 9 months ago.

I hope it works!! Just be sure not to move any of the heater controls after re-installing the fuse for at least 2 minutes.

Customer: replied 9 months ago.
i am not optimistic since we didnt replace anything...
Expert:  Derek Werner replied 9 months ago.

Normally what happens is the notch will move past the 2 lines on top of the actuator then this causes the system to not work.

Inside the actuator is a position sensor that is used by the HVAC module and it needs to be in the proper position to work correctly.

Expert:  Derek Werner replied 9 months ago.

Well you have already replaced the actuators correct? The actuator is what normally fails.

Customer: replied 9 months ago.
i saw that little copper spring thing. ok doing the relearning...the actuator moved right then left during relearning
Customer: replied 9 months ago.
no still using all old stuff
Expert:  Derek Werner replied 9 months ago.

that is normal, just watch the actuator and make sure the notch does not move past the lines.

Customer: replied 9 months ago.
but the old one relearns and moves right then left..doesnt that prove it is ok?
Customer: replied 9 months ago.
the old actuator moved up to each left then right line exactly
Expert:  Derek Werner replied 9 months ago.

It could if it starts working. Unless the position sensor inside the actuator has failed. The only way to tell if it is reading correctly is with a scan tool.

Expert:  Derek Werner replied 9 months ago.

That's great! then you have installed it in the proper position.

Customer: replied 9 months ago.
ok now i am going to try the controls
Customer: replied 9 months ago.
still hot
Customer: replied 9 months ago.
no movement from actuator with temp control
Expert:  Derek Werner replied 9 months ago.

Have you tried using both the temp controls? There should be one up by the windshield and one at the rear seats.

Customer: replied 9 months ago.
Tried both; still hot.
Expert:  Derek Werner replied 9 months ago.

ok the actuator may still be out of alignment, sorry this is hard to explain.

Are there 2 notches on the nob?

And how many lines on the cover?

Customer: replied 9 months ago.
cover has 3 lines, knob has one knotch
Expert:  Derek Werner replied 9 months ago.

ok thanks there are a couple different configurations. You will need to align the notch with the middle mark on the cover.

When I am at work tomorrow I can take a picture of one to make it clearer if needed.

Expert:  Derek Werner replied 9 months ago.

If this is correct try using the new actuator.

Customer: replied 9 months ago.
that is what i did. i manually moved the doors using the actuator knob to the center. put the actuator back together with knotch in the center and installed actuator
Expert:  Derek Werner replied 9 months ago.

ok well at this point you have covered pretty much everything that can be done. Try using the new actuator, if this still does not work you will need to get that new module installed and reprogrammed. With a new module and the software programmed to the vehicle, it should work normally.

Customer: replied 9 months ago.
on the new actuator the notch is way over to the left..passed the line. is that okay...can i put it in that way
Customer: replied 9 months ago.
i dont want to open this one, cause i would like to take it back
Customer: replied 9 months ago.
when i hold either old or new actuator in my hand when i move the temp knob and neither move...doesn't that prove something
Expert:  Derek Werner replied 9 months ago.

No, unfortunately, you can not install it that way. The lines are there to keep the position sensor inside the actuator in the correct position. If it moves outside of that range it will not work.

Expert:  Derek Werner replied 9 months ago.

It proves there is a fault code stored in the system not allowing it to move.

If the new actuator has moved outside of the lines then it was not installed in the correct position when the system was calibrated.

Customer: replied 9 months ago.
ok i gently opened the new one. moved it to center. will install it and relearn now
Expert:  Derek Werner replied 9 months ago.

I was just going to suggest you try that. Like i said before just ensure when the system is calibrating it does not move outside of those lines. If it does you will need to try it again.

Customer: replied 9 months ago.
ok installed relearned. watched it again move left then right during relearning..it moved like the old one right up to the left line then right up to the right line. then tried the AC controls no cold still
Customer: replied 9 months ago.
no movement with temp control
Expert:  Derek Werner replied 9 months ago.

well darn, instead of just removing the fuses try removing the battery cables and touching them together for 1 minute. Reconnect the cables, turn the ignition switch on, do not move the HVAC controls, wait 5 minutes and try changing the temp.

Expert:  Derek Werner replied 9 months ago.

If disconnecting the battery cables does not help the module is the only other component that could be at fault.

The module will need to be replaced and reprogrammed to the vehicle.

Customer: replied 9 months ago.
that will take alot of time. my battery is hard to get to and had special connectors for amplifiers and such. maybe i can try that in the morning.
Customer: replied 9 months ago.
would you say the actuators (old ones) are fine since they are acting like the new one? and is most likely the module thingy?
Customer: replied 9 months ago.
can i just remove the neg?
Expert:  Derek Werner replied 9 months ago.

We have covered everything that can be done, and it seems you are doing everything right. Ohh ok just remove one cable and leave it disconnected for 30 minutes then.

I would suggest leaving the new one in when disconnecting the battery. Also ensure the new actuator has the same amount of pins as the old one. You may have a wrong part.

Expert:  Derek Werner replied 9 months ago.

yeah you are right it is most likely the module if it still does not move.

Expert:  Derek Werner replied 9 months ago.

I am going to call it a night! I will be back on tomorrow to check back in.

If you could kindly rate my service it would be very appreciated. I will continue to work with you even after rated, and get notifications about any other questions you may have. I only strive for 5 star excellent service, Thank you for being a great customer.

Derek W

Customer: replied 9 months ago.
ok but can i just remove the neg side of battery? or do i have to do both?
Expert:  Derek Werner replied 9 months ago.

No just remove the neg cable. I am glad you told me about the stereo system.

Customer: replied 9 months ago.
ok thanks
Expert:  Derek Werner replied 9 months ago.

If you touched the cables together and you have a capacitor it would not turn out well. Just leave the one cable off for 30 to 40 minutes.

Expert:  Derek Werner replied 9 months ago.

You might even want to wait even longer having the aftermarket stereo. The capacitors can hold voltage for a long time.

Expert:  Derek Werner replied 9 months ago.

Thanks for your patience have a good night.

Expert:  Derek Werner replied 9 months ago.

Hi,

I am checking back in. Have you had any luck getting the rear air conditioning to work on your Escalade?

Customer: replied 9 months ago.
well i guess i will have to scrap the caddy. it was nothing that you mentioned , mechanic says is is the entire rear evap. he says the outer shell where the doors attach and the actuator is cracked. and to buy a whole new system with everything salready mounted and installed would be cheaper than him removing all the inside components from old case and draining and replacing all fluids. if i can get him to do the just case for parts it is about 200$ parts 1200$ labor. if i can get on already put together parts about 500$ labor 600. either way...waste of time and money. not happy
Expert:  Derek Werner replied 9 months ago.

I mentioned the door could be broken. Sorry to hear it was the housing assembly. I was just trying to walk to through all of the steps to diagnose the actuator and check the doors. It is not that bad of a job to replace the unit. If you have the a/c system drained by a shop you can replace the housing assembly yourself if you are up to it.

Customer: replied 9 months ago.
well he says doors are fine it is the notches or holes that the doors mount to in the case are broke. well they are saying almost 1500. i would if it was the winter here....this is phoenix and it is 116 outside. working with no air in the back of the caddy for hours on end is not something i can commit to. it is just a shame for a 189$ case , it will cost 1200$-1400 to fix. if i just knew how to manually move the doors so it was cold all the time that would be fine for now.
Expert:  Derek Werner replied 9 months ago.

Yeah, i get that, way too hot in Pheonix. I lived there when I went to automotive school; know what you mean I never left AC.

You said when we were talking you moved the door by hand and got it to blow cold air. I would just move the actuator in the cold position, install it and leave the connector disconnected so it doesn't move.

Customer: replied 9 months ago.
yeah true, i have it down at an aamco getting a second opinion...i had an ac check coupon for there.
Customer: replied 9 months ago.
i also have my auto ride control go out...so looks like i need a new compressor and two air auto ride shocks for rear...those aren't cheap either
Expert:  Derek Werner replied 9 months ago.

That's an excellent idea on the second opinion.

The air ride is a common problem for GM vehicles. The compressor stops working, causing the rubber bladder on the rear shocks to tear.

At my shop, we buy shocks and compressor rebuild kits for a much lower price than the GM units. I just cant think of the name of the company right now. I will find out for you on Monday when I am back at work.

Customer: replied 9 months ago.
now all i have is those pesky steering wheel controls...they go out all the time...the lights..and the are soldered in to the switch so you have to replae the entire switch. i dont want to accidentally set off the air bag...shops want a bunch of money to replace those all but one is out.maybe i will just leave those. ok let me know. i have a wholesaler here in town i can get each part comp/shock/shock for about 359 each
Expert:  Derek Werner replied 9 months ago.

That is expensive, you can find a Dorman compressor for 200 dollars and then shocks for 350 on Amazon.

As for the steering wheel controls, all you need to do is disconnect the battery, and remove the steering wheel. You won't set off the airbag by accident by disconnecting the battery.