Hello All,

I've been experiencing some inexplicable problems with a couple of different systems in my vehicle. I'm hoping someone has heard of these problems before and can maybe give me some input on what my problem might be.

The vehicle in question is a 1997 model Oldsmobile Regency. (Just Regency, not a 98 Regency.)
It has the 3800 Series II 3.8 Liter 6 cylinder engine. The engine is coupled with a 4 speed automatic overdrive transaxle. It's a luxury model with power everything, leather interior, and dual climate control.

The first question I have might be transaxle related, but I'm not sure:

Sometimes, when I'm accelerating softly (between 1,500 and 2,000 RPM) and I am going between 35 and 60 MPH, the car kind of "surges." It feels like the car can't decide whether it wants to downshift or stay in the current gear. It's almost like the torque converter clutch disengages for the downshift, but the transaxle doesn't downshift, and then it re-engages. I could be wrong about that though, the transaxle may not even be the cause. It doens't feel like an engine misfire, or anything like that. I'm leaning more towards the transaxle having a problem because it does it most often when the car coasts down a hill and then starts up another hill with the cruise control engaged. If I maintain the same pressure on the gas pedal, the car continues to lurch somewhat until I either get to the top of the hill, or reach a certain speed. The only way to make the transaxle (or car, or engine) stop lurching is to either let off the gas slightly, or give it more gas. If I let off the gas, I stop gaining speed, or I start losing speed (depending on whether I'm on a significant hill or not.) If I give it more gas, the transaxle downshifts and I accelerate. But I have to deal with the lurching if I want to maintain, say 45 MPH, up a hill.

I found a bulletin on another web site, evidentally GM was notified of these vehicles having this problem. Here's what I found:

Component Description:
1. VEHICLE SPEED CONTROL
Bulletin Number: 050604058
Bulletin Date: SEP 2005

Vehicle: 1997 Oldsmobile Regency
Summary:
INTERMITTENT CHUGGLE OR FISHBITE ON LIGHT ACCELERATION OR AT HIGHWAY SPEEDS WITH NO DIAGNOSTIC TROUBLE CODES (DTCS). (NHTSA ITEM NUMBER - 10017568 )

Any ideas or clues as to the nature of this problem? I tied to look a vehicle speed sensor for this vehicle on Advance Auto Parts' web site, and they said there was no such part for my vehicle.

The second issue I'm at a loss to explain is related to the climate control system. This car is equipped with dual climate control (the driver and passenger can set different temperature settings for their respective sides of the vehicle.) The main control center is fully digital, I don't have any sliders for hot or cold. I tell the car what temperature I want it to maintain, and it is supposed to run either the air conditioning, OR the heater to maintain that temperature. The passenger door then has a knob that can adjust whether the passenger vents blow warmer or colder air, depending on their needs.

Well, when I turn on the system, I get either hot or cold air (whichever I have selected) on the driver side. However, the air will NOT come out of the middle vents, ONLY the defroster and heater vents. It doesn't matter what I choose on the air-flow selector, the air will only blow out the heater and defroster vents. However, if I leave the system on "Upper" for a long enough time, eventually the air will start blowing out the middle vents ... until I turn the car off, and then when I start it again, the air goes back to the heater and defroster vents. Now for another interesting twist ... the passenger side air vents behave much the same as the driver side vents do - except that you ONLY get heat on the passenger side. I'll get ice-cold air conditioning out of the driver side vents, and hot air out the passenger vents. This happens regardless of what selection the passenger temperature control is set to, or even if I disable the passenger side controls altogether.

With all that said, has anyone heard of, or experienced these problems with any GM vehicle before? I did some research and found that I can buy a replacement control center for my vehicle, but I also found this "vacuum modulator" and other different things that I guess are mounted behind the control panel. Do you think my actual control module is bad? Or maybe something else?

I apologize for writing a book here, but I wanted to provide as much information as I could about the problem. I thank everyone in advance just for taking the time to read this, and any replies or suggestions would be very much appreciated.

The second problem is a TSB for later vehicles. I couldn't find the TSB under 97 Regency, but I had recalled seeing the same type of problem for my Intrigue. It talks about how the one side will cool and the other will stay warm.



So, basically, the door actuators are worn out. I would check with the dealer to see if they have an improved climate control module for your vehicle.

TOC Admin
Brando

That makes sense to some degree ... I used the information you provided to attempt to locate a list of parts related to the HVAC system. (I'm not sure what HVAC is supposed to stand for.) I found several parts on ACDelco's web site, but nothing called an "HVAC controller." I don't really understand what these "door modulators" are. If I am interpreting all this correctly, then I am assuming the following:

There's an electronic control module (HVAC controller?), which is mounted in the dash board. This control module contains the buttons, knobs, and switches for turning on the heater, A/C, defroster, fan, etc.

I also have the passenger temperature control knob mounted in the armrest on the passenger side front door.

I then have some form of sensor (door TEMP actuators?) mounted in the two front doors.

These sensors report the temperature of that side of the vehicle to the main control module, which uses the data to determine how cold or hot the air needs to be to properly cool (or heat) the given side of the vehicle.

My door sensors are NOT bad ... but my control deck has a flaw that causes the unit to malfunction if it loses power. So, I need to replace my control deck, and that should, in theory, fix my problem(s).

Did I interpret your information correctly, or am I way off base? I found a remanufactured module on ACDelco's web site, the picture verified that it is indeed the right part (unless I'm totally off base.) If you'd like to check it out, the ACDelco part number is 15-72200. They call it "CONTROL,HTR & A/C(REMAN) With RPO A/C FRT AUTO/AUX CONT(CJ2)"

Thanks for your previous post, I think I'm a lot closer to understanding this problem. (At least, I hope I am.)

Hi Olds1897to2004, hello everyone,


HVAC = Heating, Ventilation, and Air Conditioning. I think Heating, Ventilation, And Cooling would be more accurate. But what do I know?


Should be doors, in the ducts, that mix air from the cooling coil and the heater core. They would modulate the cockpit temps to those levels set by the driver/passengers.

The motors that move the doors might be called door modulators.

Don't know if they are electric or vacuum operated, but a vacuum leak could cause the same symptoms you see in both problems.

Regards, Norm