What year is your car? Toddster has good knowledge on the HVAC system. If he don't chime in, send him a PM.

My ears where ringing......


It'* more than likely your airmix actuator. Typical broken gear syndrome after battery disconnect.

If you own a 1992 to 1999 the procedure is the same for replacing the actuator.

Do a search here for 'trailnuts' it'* a step by step write-up on replacing it.

Let me guess you have a 1996?


Here

Airmix actuator replacement procedure

I don't know what yr your car is, but the ECC shouldn't clear, if you turn off the ECC with the key ON, then disconnect the battery. But you are there so...

That blinking temp light indicates your ECC is going through a re-learning process. That includes the opening of the draft door by the actuator control arm. The actuator arm runs through a full test cycle each time. It fully opens, then closes to a point of partial flow. It "sees" how that works. Then next time you start up it does the same thing again, but takes into consideration how "well" the last try did. To get it "right", it can do it anywhere from a few times to 41 starts.

Many people get hosed with this testing cycle going on because the stinkin' plastic gear which holds the arm gets cracked or gunked up in a area it hasn't used in a long time. The arm gets stuck somewhere, and so does the door.

If your system operation is OK, you have run into cold weather, and you want to "train" it quickly, here'* what you can do. Start the car cold and put the (not auto) manual heat on. Take it for a 5 minute trip, bring it back and turn the key off. Do not turn off the ECC. Restart it and go for another similar ride. Repeat this until the engine is fully heated up. (And you're going to do it more times)

Now, the next time you do it, you will start down the street and you''ll notice when the light starts blinking, there is a sudden draft of real cold air. That'* the door cycling open. When it stops blinking you will notice it'* not quite as cold as the short draft. Each time you repeat this process, the system will be a bit warmer.

Again, this whole thing can take a few trips or a whole lot to get the heat running reasonable. that cold air burst is because the door is letting in more cold air than the heating unit can come close to handling.

A main contributor to the difficulty of this process, and lousy HVAC conditions in general, is the interior temperature sensor. Danthurs has a quick tech article on it.
https://www.gmforum.com/showthread.p...erature+sensor

A friend of mine has been a mechanic for 40 yrs, and is a fan of Bonnevilles and the 3800 (probably because he has made a $kazillion replacing gaskets and cleaning the door panel ground buses) He maintains that he has straightened out 10-15% of all bizarre ECC behavior by cleaning that sensor.

Some people have so much dust in the openings, no internal air gets directly to the sensor. It is more effected by the temperature of the plastic surrounds. Even that is skewed, because the tiny sensor itself is completely gunked.

The sensor is one of the two most important inputs for the ECC. Because of the programming in the ECC system, bogus readings can cause anything from wierd fan and vent behavior to never getting the right temperature from the climate control.

These ECC'* and the associated air flow systems behave in a virtually organic way. They are more like plants, than engineered devices and mechanicals. I don't know if sentiments have changed, but the majority of us who have them are just happy if they can get heat when it'* cold, and a/c when it'* hot. Precision "Climate Control" is very rare.

See how the "learn" goes. If you need a lot of starts and aren't getting decent results.. the actuator arm, which the guys mentioned above, is a likely culprit. It is sticking for some reason.

The one in my "98 SSEi, definitely has the stinkin' compromised gear. It is only replaceable and not repairable. Which means i either tear most of the dash apart for a clean replace, or I do a Helen Keller blind replace, by feel, from under the dash.

I did what used to be called a "redneck repair". If you just pull the glove box, there is hole in the back where you can see the arm operating. I could see it wasn't open/closed properly, so i took a longhandled, diagonal headed, crescent wrench... with the ECC operating at what should have been a decent heat level.. I shoved and jabbed the arm around 'til I got a hot flow.

Again I'll repeat, those arms get caught because of the full range use of the stinkin' plastic gear during the "learn". If you get snared by it, the object is to get the damaged part of the stinkin' plastic gear, out of a normal and satisfactory operating range. A "normal" range is less than the full 360* of the stinkin' plastic gear.

If the stinkin' plastic gear has broken completely or close to it... you may have to leave the wrench in place and adjust it by season. Then it'* called the White (Brown or Black etc, depending upon your ethnicity) Trash repair.

I jest, but the programming of the ECC is so overengineered, that if one area is screwed up, the ECC starts making assumptions which aren't true, and your HVAC system will develop weird habits.

One example is the "Mystery Fan". Should you have the bad fortune of changing to a 180* thermostat during a protracted period of extremely cold weather, ...and you have an excellent cooling system and a fast thermostat which prohibit the coolant temperature from ever going above 185* for more than a few minutes... when the fan should be blowing, the Mystery Fan will work at its own discretion. Sometimes blowing, some times not at all, sometimes suddenly starts blowing 15 minutes after it should have started.

This behavior is often attributed to the blower control module or the blower motor itself. And if not during this rare confluence of the events I mentioned, it probably is one of those.

What is happening in the scenario I outlined... the ECC is noting that it is very cold out and it is growing more tentative (actually restricted) about blowing extremely cold air past the heating coils, because the operating temperature of the coolant system doesn't spend enough time in the anticipated transfer temperature range of 195*. To over-simplify, the ECC doesn't want to blast you with what it assumes will be cold air instead of heat, plus hold the operating temperature of the car below minimal extended operating temperature requirements.

Two years ago, I froze my wife going to work for more than a week. I really wanted the 180* stat in the car, because the car was had a history of going through UIMs like some people change their underwear. I finally threw in the towel and swapped a 195* stat back in. The Mystery Fan disappeared fairly quickly.

So these things are funky. The good thing is there is usually a workaround.

It'* my understanding that if you can move the actuator with a screw driver than the gear inside is shot.

Think about it.......the air mix actuator is electrically moved. A signal from the A/C controller tells the actuator to move in either direction.

If the gear was not broke than the arm would only move when electronically moved.

Look at it this way.....no power...no gear movement unless you force the gear to move and would hear clicking noise forcing it'* movement.


I'm still thinking your needing a new air mix actuator.