Climate control - Air flow and temp flaky

[edwinn]

1997 Riviera - 3.8 Liter, L36 - 141,052 miles

We went on a 435 + 435 mi round trip in the past week and the Ms complained of cold air coming in on the floor. She had the Pax (passenger) Temp control to Max hot, but that's not the way to correct it. I've know there was a slight issue with the Pax side for three years.

Yesterday I ran some tests sitting in a parking lot with OAT (outside temp) very cold.. maybe 15° F. There was no setting where air would come out the floor vents. Further the rectangular dash vents were blowing Hot air, while the circular 'panel' vents were blowing cold air. Please advise on what a Tech would look for in the case of: 1) air not coming frok the floor vents, instead coming out windshield vents even in bright sunny day, 2) Pax side noticeably colder that driver side.

I have 3-Vol GM service manuals and can track along pretty well.

Thanks,

-Ed

[Tech II]

What do you get for temps, when you set the temp for 90, and vent position, and the vehicle at normal operating temp(temp gauge is 190F)....dual is off....

Then change to heat position.....

[edwinn]

Originally Posted by Tech II

What do you get for temps, when you set the temp for 90, and vent position, and the vehicle at normal operating temp(temp gauge is 190F)....dual is off....

Then change to heat position.....

Ok thanks.. you're asking me to: 1) set target temperature to 90F, and turn Pax control to OFF (or center).. 2) change from Windshield, to Mid, to Floor airflow and note where output air is coming from? and what temp the airflow is?

What is: "then change to Heat Position?"

It will be in VENT position. I run VENT most of the time unless it needs dehumidification. (but do run AC now and then to keep it 'juiced up')


-Ed

[Tech II]

That sounds right....

[edwinn]

Originally Posted by Tech II

That sounds right....

Have run some tests when it was FRIGID cold the other day, and drove it around for a few hours yesterday.

Here is what was observed:

1) There is airflow out the WINDSHIELD vents at all times when Climate Control System is running, no matter what the mode or airflow selected,

2) after cold start-up, there is WARM air coming out the DRIVER windshield vents, but cool air coming out the Pax windshield vents.

So the issues are "airflow always out the windshield vents", and "imbalance between Dvr and Pax sides." I removed the Dvr closeout panel/cover and can see THREE actuator motors up there. Also got several printouts of the system from a local GM dealer parts dept.

Is there a HVAC checkout procedure/service that dealers run on the Riv? I see fifteen DTCs for the climate system in the shop manual, but my OBD2 cannot read them.. only engine codes.


-Ed

[edwinn]

Update on the airflow situation. I've removed the close-out panel underneath and can see the DRIVER side actuators.

Went to the dealer and got a diagram of the system. Which actuator motor controls the windshield DEFROST airflow? In the following images, there are three or four door/valves and two of them seem to be linked.




Also have the Shop manuals that give more detail. But they're not specific enough. Also what would be a good SECOND source for actuator motors? You can see the dealer price for them in the diagram!! Wow


Will have to test the system more in warmer weather. IIRC yesterday the airflow was split between floor and defrost, but the Pax side is definitely COLDER that the Drv side. Moving the Pax control to +3 or +4 makes it discharge warmer air. It's not balanced too well.. at all!!


-Ed

[edwinn]

The Riv is going in the shop next week for climate control diagnosis. The adviser guy says GM has discontinued Riviera CC parts, and says the sensors are NLA. The symptoms restated are:

• Air always coming out windshield vents regardless of setting,

• Imbalance in driver/passenger side air temp.. passenger side COLDER.

There's one other past symptom to report. If weather was fair (temp 70-80°F) one of the airflow actuators would `hunt´ meaning in would cycle back-and-forth at a 3-5 sec rate. That many be the control that failed.



-Ed

[edwinn]

Originally Posted by Tech II

What do you get for temps, when you set the temp for 90, and vent position, and the vehicle at normal operating temp....dual is off.

Yeah.. I'm going to run the above test again in a more formal way. With the motor at Norm Op Temp. Will being a spare floor mat along to kneel on pavement and observe the Mix door shaft positions or BOTH the L and R sides... and use a handheld IR Thermometer to record TEMP from several outlets. That should provide DATA.. not kind'a warm, cool or really hot.




So the plan is to go VENT position, set temp to COLD (60°F) then HOT (95°F) and measure IT temperatures at the discharge ports, and also maybe photos of Mix Door shafts.


With that kind of test, and observing Mix Door positions.... well we'll see.


-Ed