Alright folks, let get the salutations out of the way real fast and in a hurry. My name is Garrin, I’m from southern Missouri. I have a 99 coupe (it’s triple black & super sexy). This is my first post (shameful, I know). I usually lurk in the shadows and give silent nods of approval to good advice, and keep to myself. I am very mechanically inclined, with a vast knowledge of pretty much most all late model GM vehicles. I will never ask for anyone to spoon-feed me answers that I am too lazy to research myself (just proper forum etiquette, c’mon now).

-Now that all that is out of the way, and my account is active…. Let’s get this problem aired out.

I have the Auto climate control (RPO CJ2)
Repeatedly retrieving codes B0361, B0363 & B0441 since I purchased the car, and the driver side temp control has always defaulted to hot (no matter what setting was selected).

I Pulled the left side temp actuator and the drive gear was broken (as expected). I epoxied the gear, reinstalled the unit and went on to initialize. It will do the initialization process and default back to hot. I removed the cover to further investigate the actuator and found that the potentiometers resistance remained constant (8.724ohms) throughout its full range of motion. – ORDERED REPLACEMENT ACTUATOR.

The replacement I received was a Dorman part. I followed the instructions for installation by removing both fuses that control the HVAC system (#18 & #27 in the pass side kick panel fuse box), then install the actuator and powered up the system. The actuator initialized, then reacted in the same manner as the actuator with the bad potentiometer, so upon further investigation I opened the Dorman actuator up and noticed that the Dorman unit was without the traditional gear driven potentiometer from the OEM unit, and that it received it’s resistance reading from a flat half-moon sweep potentiometer that will not be able to be manually indexed if the need arose.

-After replacing the bad OEM actuator with the Dorman unit (even though it has the same end result) I am left with only B0441.

If I understand the information available for this system… When the system initializes, the controller sends out a signal to the actuator that tells it to go find the full open(hot) & full closed(cool) positions available by the blend door and report that information back to the control unit in a resistance measurement of the potentiometer. The controller is hard programmed to know that those locations should be with in a certain range (6-249) and if the actuator is able to turn further than the controllers preconceived notions of where the stops should be (0-5 or 250-255), an out of range code will be set and the controller will default to its “fail safe”. Which sends the actuator to the depths of Hell and delivers you heat to keep you warm…. ALL SUMMER.

What I am getting at, is that I have watched both actuators try the initialization process, and can see the actuators turning past the expected stopping points (both ways) before failing and defaulting back to the full open(hot) position. This leads me to believe that I have either a bent or damaged blend door or blend door linkage. Or I received a junk Dorman part (not out of the realm of possibility). Or worst case scenario would be that if there was some type of internal damage to the air handler that allowed my blend doors to travel further than designed. ← HOPE NOT

Is there anyway to definitively confirm or rule out the blend door itself or its linkage being the culprit? I’m 6’1” 220lbs and upside down in the floorboard of a C5 is not a fun place to be, but I really don’t want to pull the dash out and repair the air handler AT ALL, if I don’t have to.

I have a couple hours tied up in this so far and the weather turned off pretty rough so I am taking a break to collect my thoughts... and yours.

I hope not only that one of you guys has some helpful information for me, but that my lesson on how this system works helps someone in my situation later on down the road.

 

What dorman part number did you buy? Should be 604-106 for the duel zone control. That's what I put in my 99 and they work great.

 

My part# is 604-111. Not sure the difference, but that's what rockauto.com claims is the correct part#.

 

We have another here trying to get that part number to work. It doesn't. Go to O'Riellys site and put your info in. Shows the number I gave you plus a 107 and it's for the standard system.

Was your original part 15-72971?

 

Thank you for that info. The original had a sticker that looked like it used to have the part number on it, but it wasn't clearly legible. I might be able to decipher it if I took some time to try, but since I was getting a Dorman, I honestly never gave it a second look.

However that still doesn't address the fact that both actuators spun past the predetermined stopping points that are marked on the actuators themselves, before coming to rest at the 'hard' stops of the blend doors travel.

<correct me, if I am wrong>
The system relies on the physical 'hard' stops in the blend doors movement path to stop the actuators travel and report that position back to the controller as the correct "range limits".

This information is the combination of several other threads that I have read as well as the gospel from ALLDATA & Mitchell OnDemand.

 

I don't remember if the original actuator had physical 'hard' stops, don't think it did. I had mine apart a year ago. I put that part number you have in the search on ebay and their vendors say it doesn't fit a 99 corvette. So there must be something different in the electronics.

I just checked several other places and they all said that your part does NOT fit a 99 Corvette.

 

I'll post some pics later, but the hard stop is the door itself. I happen to have a complete hvac box in my hands
The stops on the actuator don't come in contact with the pivot.

 

Go to the Dorman site, 604-106 IS the part number they make for your car.

Put in the correct part and then see if you have problems.

 

Not sure if it's just a typo on the RA application illustrated parts guide page, but the range of OE GM part numbers listed includes "89018375", and the correct (current) OE part number number is "89018365", for which the correct AC Delco direct equivalent part number is 15-72971. I agree with 92GA.

https://www.rockauto.com/catalog/mor...nid=509&jpid=4

FWIW, Dorman is a company that contracts with a wide variety of manufacturers that supply repair parts to them under their proprietary brand name.

 

With the blend door fully open to hot the passenger actuator looks like this. It lines up with marks on the housing.

 

Great class...I learn more here than I ever did in school...maybe that's why I'm here.

 

Me too. Working as it should.

 

Sorry for the lack of updates. We had some threats of harsh weather the last couple of days and I had to move the car into the corner of the garage where I couldn't open the doors to work on it. So I could get my truck out of the hail.

I will see what I can do about getting RockAuto.com to replace the actuator they sent me with the correct one.





I know that my blend door is able to turn further than those marking on the front of the actuator when it runs the initialization process. Which is what I have been trying to convey since the beginning.

The actuator (fresh out of the box) has no idea where the stopping points for cold & hot are. The controller doesn't really know where they are either. The controller knows "abouts" where they SHOULD be, and the markings on the actuators are there for troubleshooting purposes.

When the initialization process starts, the controller commands the actuator to rotate towards the hot setting until it bottoms out the blend door and can no longer move. The actuator then sends that locational information (as a resistance (ohm)) reading back to the controller. The controller then commands the actuator to rotate toward the cold setting until it bottoms out the blend door and can no longer move. The actuator then sends that locational information (as a resistance (ohm)) reading back to the controller.

The controller then evaluates the locational information and determines if one or both of the locations are acceptable and within the expected range. If they are, you get to make all the climate decisions and stay comfortable.... if they don't fall into that range, it will default to its fail-safe, which is the (even out of spec) max hot position.

Like I said I will be contacting RockAuto for the correct replacement actuator, but the main question is... is it a common issue to have overly excessive blend door travel? how much blend door travel is considered overly excessive? Remember that: when I reinstalled the OEM actuator (with bad potentiometer) after I epoxied the gear, it too rotated past the markings on the front of the actuator casing. Which, in a nutshell is what got me overly excited and worried that I have internal air handler damage. or blend door issues that will require complete dash and air handler removal.

When I say excessive blend door travel, it is rotating past the marking on the front of the actuator casing my a solid 1/16" to maybe 1/8".

 

I never paid any attention to where the actuators lined up after I installed mine. I know that it rotated the door all the way closed and a couple seconds later it rotated it all the way open. When I moved the temp control it either opened or closed the door, so I put it back together.

As long as the door itself isn't broke, it should work with the right actuator.

 

Recommendation/Instructions:
Air mix door mechanical linkage build variance or wear may cause a slight over travel condition of the door. Whenever battery power is interrupted from the HVAC control module, it will perform a recalibration of the actuators once reconnected. During recalibration, the HVAC control module will drive the actuators to their minimum and maximum travel extremes (5 and 250 counts). The module issues a travel command to 0 counts, but expects to see feedback slightly less as the door hits the cold stop in the case. The module will then calculate a travel range from this data and compare it to a calibrated range within the HVAC control module. If the actual travel range is not within the calibrated expected range, the actuator will be considered not calibrated and the DTC will set and the temp door bias toward warm is the DTC failure action.

An actual range below this limit suggests an obstruction (something stuck in the door limiting travel).

An actual range above this limit suggests an over travel condition (wear, damage foam seals, etc.).

The range fault code can only be detected following a check of the left air temperature actuator travel range. The left air temperature actuator travel range check can only be initiated by disrupting power to the HVAC control module (disconnecting the battery for 60 seconds) or with the scan tool.

If thorough diagnosis of the electrical system shows all electrical components to be ok, replacement of the HVAC control module with a 2001 or newer part number is required

If this has already been done, a reset/re-time the actuators internal feedback sensor to lag slightly behind the actual position can be performed. Open the actuator case and reset the output gear and sensor gear by only 1 gear tooth. This will allow a feedback of 4 counts when performing learn.