I was wondering if someone could shed some light on the HVAC system and to where my problem my reside. When the system is turned on, the passanger side blows either outside temp. air or , if the A/C is activated, it blows cold A/C. I can't get it to blow heat on the passanger side.

I understand that there is supposed to be a 5 or 6 degree temp. difference between the drivers and passanger side. What is suspect is that I can have heat on the drivers side and cold A/C on the pass side. A much bigger difference then 5 degrees.

So, do you think that my HVAC needs to be replaced? Also, I checked for error codes and there are none present.

Thanks in advance,

 

Are you sure you're not throwing any codes? Sometimes error codes won't display a message on the DIC unless they are severe. Did you Hold down "Options" and hit "Fuel" 3 times? The HVAC responded with "NO CODES" ??

I am far from a tech. I'm just experiencing HVAC problems myself. I followed the manual and one of the first steps to diagnosing the problem is taking a thermometer and placing it in the center vent and testing COLD (60F) and HOT (90F). I don't have the book in front of me or I would post more.

Goodluck.

 

Thanks for the reply. Yep, I am sure about the codes. None are present. I did hold down the options button and hit the fuel "4 times".

I have the shop manuals, but they are pretty confusing for a novice.

Revman

 

I recently experienced the same problem (amongst MANY other HVAC problems). First of all- when I would turn my car off- my blower motor would turn on about 20 seconds afterwords... Which led to my battery dying, and I went thru 3 batteries before one day I just happened to be standing by my car still when the motor came on- it would stay on until I started my car. It would also go to the highest level when the system was turned off if I was driving it. To make a long(er) story short(er) it ended up my blower motor control module (little black box right by the blowor motor itself) was bad. When I replaced it- I experienced the same problem you have. The p/s would not differ at all in any way despite what I put the controls on. Also- no matter what setting I put the control on, it would blow air out ALL the vents- the in dash vents, the lower vents for the feet, and even out the defog vent. I thought maybe the head unit was possibly bad. I still have my old head unit laying around in my garage that has the dim LED lights that I replaced. So I plugged it in, to see if it did anything. Unfortunately, all the same problems stayed. I then did a search and found that some people had experienced a leak in the vacuum line that feeds the system from battery acid leaking. I knew I had completely drained 3 batteries past the point of no return, so I ventured into checking under the battery tray. Once I got under there, I did not find much acid residue- only a little bit of whitish blue flakes. I found the vacuum line that came from inside and traced it to the inner fender. I looked real closely, and found 1 place that may have been leaking possibly. So I cut it there and put a small 1" piece of hose in place and taped it all up with electrical tape. I then saw another line going to the same spot inside the fender. So I followed that and it lead to a 2-way check valve that was plugged into the canister inside the fender. After taking off the check valve, I temporarily patched the lines going to it together, and tested the system- everything worked as it should. The vents changed from upper to lower, the dual zone worked, and everything. So I replaced the check valve from O'Reilleys. (It's off the shelf- don't bother asking the moron behind the counter to look it up for you because he won't find it). But after I replaced it everything works perfectly now. And I can once again enjoy my Vette in the hot Oklahoma summer time. Who would have thought a $3 part could cause such havock!

Hope this helps.

 

Wow, that is interesting. So it was this check valve that was causing your problem. Was the part number on the valve? We you able to tell if the valve was sticking once you located it.

Thanks for the info, I will start looking at these vacumm hoses and see if I can locate any leaks.

Thanks,
Revman

 

The part# for the one I bought is 47150. I think the brand name is "HELP!". Or maybe its "MOTORMITE" It was in a red box... It says "TWO WAY CHECK VALVE"

I got an e-mail from a member and I thought my reply may be helpful to others. Here it is:

I'm not sure if the vacuum line or valve is your problem, but it was mine. To get to the valve, you must first remove the battery. Then remove the 4 bolts holding the battery tray on the frame bracket. Then look at the firewall where a hole is for wires coming out of the inside of the car. With those wires, there will be a plastic black vacuum line coming out and it turns towards the p/s fender. Follow that line- it goes inside the fender right by the intake behind the front wheel. You will also notice another black plastic vacuum line going to the same spot. They both go to that check valve. The check valve itself is probably only like 1.5~2" long. It has fittings on the front and the back for the lines reffered to above, and 1 fitting on top that plugs into the canister that is mounted right there by the intake. You can pull down on the valve, and it should then come free of the canister. Then, pull it out, and you will see the 2 lines still hooked on 1 from the engine, and the other that goes to your vacuum relays behind the p/s under dash. Unplug them and replace that valve. You should be able to get it at any parts store. It was about $3.xx at O'Reilleys off the shelf.

 

Thank you very much for the information. I this definately give this a try. I will let you know how it goes.

Here is a picture of the Motormite 47150. Does this look like the valve you replaced?
http://www.partsamerica.com/PartDeta...rtNumber=47150

Revman

 

Great thread!! Great post by ChevyChad!!! This is one for the archives. If this goes wrong one day on my car.

 

Thanks for the info. Like Stock Man, this will be put in my archives.

 

So what you guys are really saying is that I need to get busy, tear my car apart, and see if this fixes the problem. I will try to get to it tonight.

Revman

 

Not to discount the above resolutions, but I think you should consider that the problem is the passenger airflow mixer door inside the dash that's stuck in the "cool" position.

The way the dual-zone plumbing works is there are 2 mixer doors (one for driver and the other for passenger ducts) above the blower unit that provide the dual-zone temperature variance. These doors are positioned based on the temperature setting to mix warm and cool air to deliver the right air temp to both sides. If you set the passenger temp **** in the middle, both doors are in the same position. But when you change the passenger **** to, say, be cooler than the temp setting, the passenger mixer door is biased to allow more cooler air to that side than the driver's mixer door.

It sounds like the passenger mixer door is stuck in the full cool position, so it only delivers "unheated" air, i.e. outside air or A/C cooled air.

Try reseting the unit. There are 3 fuses that you can pull to reset the HVAC system. When you put the fuses back in and turn the ignition to ON (don't start), the HVAC will go through an initialization routine and move all doors to their extreme open and closed positions to calibrate them. Remember the dual zone uses electric motors to move these doors, not vacuum like the manual HVAC unit. Let the unit finish it's calibration routine and then try the unit.

If that doesn't work, then I suspect the actuator motor for the passenger airflow door is stuck and needs to be replaced.

Good luck.

 

Thanks for the advice, guys. Since pulling 3 fuses was much easier than the other procedure, I decided to try that first. The 3 fuses I pulled were the 2 labeled with HVAC in them, the 3rd was the A/C use in the engine bay fuse box. Was that the correct 3 JC in XTC5,? If so, that did not seem to clear the problem, so next I will replace that check valve.

Stay tuned!
Revman

 

Any more ideas Guys?

I changed that check valve and inspected the vacuum hoses, but the problem still exists.

Does anyone know where the p/s mixer door is located. Maybe that is stuck. Also, how would I check the p/s actuator?

Thanks,
Revman

 

i had the same issue tried several fixes found out the low side shrader valve was leaking and i was .50 lbs of freon low now it works perfectly. For me it was worth $35 getting the system recycled and refilled .At-least its a possibility ruled out

 

So ready what u have stated would be the same problem as mine i have cold on drivers side hot on passenger side every thing works except getting cold air out passenger side.my ac unit is brand new every thing.an no codes.asking for input because im getting frustrated.thanks in advance.

 

A little confused...so are you having HOT on drivers and COLD on passengers side or vice versa ???????

 

15 year old thread and I liked a comment. LOL

 

I found that I could check the operation of both mixing door actuators by reaching up under the driver's side and putting a finger on the output shaft. With the ignition ON I turned the driver's temp **** slowly in both directions to feel the mechanism (you can't see it) move end to end (rotation). In the passenger's side I believe I removed the glove box for access to the mixing actuator to feel for rotation when the passenger's temp **** is turned. In this case there WAS some movement, but not end to end. I removed the actuator and replaced the cracked plastic gear inside. The reason these gears crack is because they are a tight fit on a metal shaft, normal temperature expansion of the metal shaft puts stress on the plastic gear's inside bore, forcing it to crack. I used emery cloth tape to polish the shaft to a loose fit in the gear, that was the end of my problem. Incidentally, my symptoms were the same as yours. In the picture below, the passenger actuator is the white tag forward of the middle of the aluminum radio/HVAC control mount. No way to get to it unless the car is torn apart as you see here. Several Corvette parts suppliers sell these gears.