HVAC help needed

[bbgot]

Ok, I bought an 02 CC a few weeks ago, and I've been working my way through this forum when I stumbled across all the threads dealing with the transfer case switch problems.

I have noticed that vacuum is lost almost immediately after the truck is shut off. So, today I pulled the factory switch out of my truck (had the green stripe) and replaced it with a new switch. There wasn't alot of ATF in the vacuum lines, but they were wet inside. I played with the HVAC controls and found that there was vacuum hissing at the dash vent and floor vent positions only. Also, getting air out of the floor vents is not possible when turning the knob clockwise, but if I turn the knob all the way over to defrost then back counter-clockwise, the floor vents work.

I pulled the control unit out and took the vent selector switch apart and found a slight ATF film inside the switch. After cleaning, the vacuum leak is still present.

My question is, does anyone know of a place to buy only the vent selector switch, or am I going to have to buy an entire HVAC control unit?

[roadrunner]

Welcome to the forum. Can't speak to the vent selector switch availability question other than perhaps Rock Auto.com (several are listed there and you need to verify which one you have) but if you find ANY atf fluid ANYWHERE in ANY of the vacuum system components replace that T-case switch IMMEDIATELY IF NOT SOONER unless you have already just done it. Along the same lines of thought if fluid has leaked into the HVAC system you may discover other vacuum leakage points such as vacuum motors on the HVAC doors. Those diaphragms in those actuators are pretty thin and atf will destroy them rather quickly. Leaks in those actuators can cause vacuum leak noises to sound like they are elsewhere because they are pulling air through the switch and other hoses.

[bbgot]

Thanks for the reply.

Yes, I have replaced the switch. Its just damage control at this point. I'm going to pull the vacuum reservoir tomorrow and see it any fluid made it to there. I already checked the front axle actuator, and it was fine with no fluid.

I've also replaced a couple vacuum lines under the hood and there was no fluid in those either so I don't think the leak had progressed very far, even though the truck has 119k on it.

I just want to know if there's any way I can get out of replacing the whole HVAC control unit.

[bbgot]

I just remembered one thing I forgot to ask. I replaced the transfer case switch with a Dorman switch from O'Reillys. Is this part a quality piece, or do I need to go ahead and order the revised GM switch?

I wanted the GM part, but it was going to take a couple days to order and I needed to get the old switch out today since it's my only vehicle for the time being.

[HenryJ]

I don't know if the Dorman switch is good or bad. Is there a chance that the connector could have been clocked wrong on the Dorman switch?

[bbgot]

The connector is clocked right on the Dorman part, I checked the 4WD and everything functions fine with the new switch. My question is do you think the Dorman switch will be trouble-free (like the new GM switch is supposed to be) or just a temporary fix?

[HenryJ]

You're the guinea pig You'll be the one to tell us, I guess. You may be the first here to try one.

[okaussie]

I kind of had the same problem last year in my 02 CC. Got my HVAC control from Rock Auto for around $75. I have only been able to find one that has all the controls , not being able to purchase the HVAC control switch. I think due to the design of the head it would be next to impossible to swap out just the HVAC Control.

I buy lots of parts from them and they are very helpful and fast.

Bill

[bbgot]

Well, I found a new HVAC control unit on Ebay for about $40, so I'll give it a try. I just checked the vacuum reservoir and it was free of fluid, though the one-way valve before the reservoir did have some fluid in it.

I'm going to replace some more vacuum lines today as well as try to repair a dash trim piece I broke in the process of working in the dash yesterday.

[bbgot]

Well, I've been checking the vacuum lines that plug into the back of the HVAC control unit with a vacuum pump, and only two of them show any leakage. Again, there is very little ATF fluid in the system, so I think I may have gotten lucky that it didn't screw up much of the system.

Where are all the vacuum actuators located? I can see two behind the glove box, but there should be a couple more, shouldn't there? The only problem with the HVAC system is that air won't come out of the floor vents sometimes, and there is a hissing sound at the dash-only and floor-only vent positions, so I'm guessing the actuator that diverts air to the floor is going out?

[okaussie]

They are located behind the glovebox. There is a thread on the Hot Feet Fix which shows where most of the actuators are located. It is a Sticky...

Good luck. Mine was not near that bad..

Bill

[bbgot]

Well, I had some free time this morning to troubleshoot the system some more. I found that the recirculate door actuator directly behind the glove box and the defrost actuator next to the accelerator pedal were both faulty. Neither contained significant amounts of ATF, but were both slightly wet with fluid inside the diaphragms.

I ordered both actuators (AC Delco) for $30 shipped from Rock Auto. I was pleasantly suprised by how easily both of these actuators were to access and remove, from previous experiences with these sorts of things, I was expecting to have to remove most of the dash.

[bbgot]

Well, I got it all fixed yesterday. I removed all the actuators and the control unit and blew out the vacuum lines with compressed air. Then I hooked everything up to the new parts, and now everything works as it should with no vacuum leaks.

When this problem first appeared, I thought it would be an expensive fix, but it wasn't too bad.

New HVAC control (Ebay) $40
New t-case switch (Dorman) $18
(2) new vacuum acuators (RockAuto) $30
(2) cans of compressed air (Harbor Freight) $10
12 ft. of vacuum line $6

All together for about $100.

[HenryJ]

Well done.

[roadrunner]

Way to hang tough till fixed!

[F9K9]

Well done.

+1

[wnyred]

Is there only one switch in the transfer case? May seem like an odd question,but a friend that works in a transmission shop replaced a switch in my trans case. When mine failed,it would cycle the compressor on. Im trying to make sure that I don't need to replace something different.

[roadrunner]

There is one vacuum switch on the t-case for the front axle actuator and one electric switch as an integral part of the encoder motor for changing modes between 2-4hi and 4lo. I know of no others on the t-case. There are two others associated with that shift system but they are located on the dash (push button switch) and on the front axle actuator housing (position indicator switch) respectively. The only other electrical component in the t-case shift system is an electronic module located behind the right hand front kick panel. I have no clue why any of these would affect your ac compressor unit.

[HenryJ]

Is there only one switch in the transfer case? May seem like an odd question,but a friend that works in a transmission shop replaced a switch in my trans case. When mine failed,it would cycle the compressor on. Im trying to make sure that I don't need to replace something different.

I think you are confusing someone. Probably me. The transfer case is behind the transmission and has nothing to do with the air conditioning. Nothing on the transmission or transfercase will cycle the air conditioning compressor. If it does you have electrical problems much worse that can be diagnosed over the internet.

The Air conditioning compressor does have two switches. A high and a low pressure switch. Only the high is mounted directly to the compressor. This allows the system to be active and shuts it down when the pressure is too high. The other is the low and is located near or on the filter dryer / dehydrator. This switch activates the compressor when the pressure drops.

Check out the transfercase switch thread for information on that switch. It is a vacuum operated switch and there fore can not interact with the electrical switches for the air conditioning.

No what CAN happen is that when the trnasfercase vacuum switch fails. Fluid can be sucked into the controls for the HVAC. This will create problems with its vacuum operated doors. You may have that part confused with activating the compressor which it can not.

[wnyred]

Well that was what i was talking about. The faulty switch was trying to actuate the front axle,and there would be this whirring sound,real loud. That was how I realized there was a problem. My friend knew what it was relatively quick I thought he said thats what it was,maybe something trying to build compression is what he said. Anyway,that was months ago. It solved that whatever trying to cycle on and my four wheel drive works fine now. But believe my hvac controls are screwed because they hiss. My question was stupid i figured that out after i asked but then felt i had to explain. sorry lol. So basically all this vacuum line checking etc,is on my to do list.

[HenryJ]

Faulty seals in the transfercase vacuum switch leaking into the vacuum system and subsequently fouling the HVAC control is sadly an all too common occurrence.
Be sure to remove and clean the vacuum reservoir and all the slave cylinders where the fluid may accumulate. I really don't know if there is a good way to "clean" the hoses. Anything that would truly clean them , may do the same damage to them as the fluid that is already there. Replacement would be the best option in some cases.

Many have tried just replacing the HVAC control and found themselves back again replacing it when fluid in the system ruined another switch. Be thorough, and clean it out right.

This will be a very involved process. Don't be surprised that some have spent upward of $1600 on their repairs. Removal of the entire dash assembly may be part of the repairs needed.

Good luck to you.

[F9K9]

I hadn't heard of it before but, a large equipment mech recommended that I clean the ATF out of my wife's Cherokee's block and cooling system with Cascade and it really did the job. I have seen it recommended since then.

[HenryJ]

Soaking them in hot water with a little soap might just work. Great idea

[rlrnr53]

A local radiator shop reccommended using Dawn dishwashing soap when one of our graders ruptured a oil cooler. I didn't think it would work, but the inside of the radiator looked like new.

[roadrunner]

+1 on the dawn. Amazing stuff!

[F9K9]

Was that radiator mounted in the grader and you ran the Dawn with it running? I have visions of some Lucy episode with soap bubbles everywhere. Dawn would be better in this scenario but, in a running cooling system, you will want to use an automatic dishwasher soap.

[roadrunner]

Can't speak to the grader but I've used it in tractor and truck radiators and driven them with it in there. No bubbles with the system closed in all cases I encountered. Not disagreeing with your dishwasher soap idea just saying I've had good success with the dawn method.

[rlrnr53]

After replacing the oil cooler, we removed the thermostat filled it with water and Dawn, and started it and let it idle for about 15 minutes. There were a few bubbles but mostly just a grungy mix of oil, water and soap. It took about three treatments to get all the oil out. There were more bubbles the last treatment, but nothing excessive. We got more than a couple of strange looks when someone would see the Dawn sitting on the parts room shelf. This is the standard way the radiator shop cleaned cooling systems. The Dawn has very good grease cutters in it and doesn't make a lot of suds if you don't use too much.