PREFACE: Sorry for the wordy post, and for making a new post on an old subject, but I haven’t found an identical problem on the board. Nothing with a resolution posted, anyway.

Blinking Electronic Climate Control (ECC) display – the saga continues. I have come to the conclusion that disconnecting the battery can cause the ECC to discombobulate (technical term) and start flashing error codes. Often it will be the “Driver Air Mix Motor circuit open or shorted, or not calibrated” code. I recently had to disconnect the battery to replace the ignition switch and whaddya know, the ECC hated it. Last couple times this happened I used the “ignore until it goes away” maintenance policy with great success. This time, however, the ECC has become rather stubborn and I suspect it truly has a fault this time. I’m hoping someone much wiser than me can help narrow down the problem component. First a little background on why I disconnected the battery –

It was a dark and stormy night. We stopped in at Wendy’* and filled our gullets, and when we came back out, the ol’ girl refused to start. Turned the key on and everything lit up properly, but no power to the starter. Not even a solenoid click. Very puzzling. Turned out to be a broken little wire in the ignition switch that “reads” the security device on the ignition key. If that wire’* broken, the computer apparently won’t allow power to the starter. I don’t believe this had any impact on the ECC problem, other than the battery was disconnected to effect repairs to the ignition switch.

Ever since then, well over 2 months ago, the ECC has been flashing at me. I read the error code (it’* a 93 SSE with automatic temperature control, btw) and sure enough it’* an air mix door calibration problem (#40, I think). Like I said, I ignored it for a few weeks but it didn’t go away this time. I disconnected the battery and let sit for a couple hours. No change. It’* been several more weeks and the weather is getting cold enough that my wife’* complaining a bit. After reading other posts, I’ve been condemning the air mix actuator in the back of my mind, but after some testing last night, I’m not so sure. I took the glove box out and watched the operation of the air mix arm. I’m hoping someone will have some insight or experience with this and can tell me what component to change. Here’* what I’m experiencing:

(Assume the engine is warm)
1. When the car is started, the air mix door goes to full hot (to the right) and stays no matter what the temperature is set at.
2. After a few seconds the ECC display starts a-flashin’ and the air mix door goes to full cold and stays there regardless of temp setting. Motion seems to be smooth in either direction.
3. After the flashing is done it stays full cold (to the left). Occasionally, however, the air door will move and mix some warm air in. Sometimes it will move just a fraction, other times it will move to the correct position. But more often than not it stays cold after the flashing is done.
4. If, after the flashing is done, I run the temperature setting to 60 (as low as it will go), then run it up as high as it will go (90?), the door will move to the full hot position (as it should) and the blower (in “auto”) will blow at max. If I then set it at ~70, the air mix door will move to somewhere in the middle and the blower will reduce its speed like it normally would.
5. If, after the flashing is done, I don’t run the temp to 60 and just try to give it max heat, the door will typically just move a fraction and blow lukewarm air. It appears that I have to set it to 60 after flashage in order to make it work.
6. Sometimes if the car is shut off and restarted, the ECC will work properly (similar to a problem someone else had - See HEATER/AC PROBLEM posted by gomti – no problem resolution posted)

OK. So based on this data, I’ve ruled out a blower problem – that’* fairly new anyway and I have no problem with air volume. I suppose it could still be the air mix actuator, but it would consistently move the air door to full hot on engine start, and to full cold on ECC flashing. Seems to me it’* more of a controller problem, don’t you think? Problem is I’ve read many posts on ECC problems and have yet to read where changing the HVAC programmer solved the problem and I don’t want to just throw parts at the car.

Maybe the door just needs to be calibrated? How do I do that? Any suggestions are very welcome now! Again, sorry for the long dissertation.

That may have been long, but one of the best problem descriptions I've seen in a while.

I wish I had the info you are looking for, but alas, no FSMs yet. :(

If nobody else chimes in before I get home, I will look up the calibration info for you. It is basically set the ECC to full heat and move Airmix door actuator to full right. Then there is a system of temperature tests to run and get it calibrated.

The procedure may be quite different for the 93. I'll check my FSM'* tonight.

Good point. Thanks, Bill. I thought about that, but figured that the airmix actuator itself probably didn't change as much as the ECC and HVAC Programmer.

The 93 ECC has alot more on-board diagnostics, so you may be able to force it to relearn/calibrate airmix door position.

I'm a couple hours from getting out of here, though.

With ignition switch on, Press OFF and WARM buttons at the same time. The system will self-test. DTC'* will be displayed (there is a techinfo article on this).

Press fan down until it reads "02°C". You are now in diagnostic override, and can scroll UP through the functions.

Scroll up to override setting (temp) of 117°. This is the airmix valve (actuator) position. If it reads "00" the circuit is shorted. Replace the HVAC programmer. If it reads "--" the circuit is open, replace the HVAC programmer.

Full cold should read 98, full hot should read 01. You can adjust the temp up and down while in this mode and the actuator should respond. Use the ECC override to adjust the mix valve to the full hot position. If the airmix door is not full hot at this point, adjust the actuator until it is. Repeat the above procedure for the full cold position.
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As you can see, the venerable 1993 ECC'* on-board diagnsotics make this a rather simple procedure without the need for a Tech1 or Tech2.

FYI, Diagnostic mode "01°C" (get to it by fan down) will display blower PWM voltage, coolant temp, air delivery mode, inside temp, ambient (outside) temp, solar sensor status, ignition voltage, commanded air mix valve position, actual airmix position, and more.

Other functions in the Override mode "02°C" that you used above are that you can command the programmer to max heater or max AC, Air delivery mode to any vent position, AC clutch on or off, plower speed, air mix valve, and realtime ambient temp reading.

Get a Factory Service Manual from www.helminc.com or eBay in order to take full advantage of these diagnostics.

The Helm manuals are 1/2 price for cars earlier than 99, if I recall correctly. I've always bought them for each new car except one.

You should be able to work through this problem without the manual because there are many people here who are great about figuring things out. If you like to read and want to know HOW your car works, the Helm manuals are worth the $120 or so at full price.
BTW: Helm sent a corrected set of 3 manuals for my 98 Buick because there were errors on something in them. They just showed up at my door about a year after the news ones-they didn't send a note to verify address or IF I wanted new ones-they sent them.

It'* 99+ and the sale might be over.

Thanks to Billboost for correcting. It says 99-2001 now.

I could have sworn in the past there was a post somewhere that said the older manuals were on sale--I assumed it'* because many of those are on DVD/CD and covered by purchasing one CD at $300? or so. There was less demand for paper version so they were unloading stock.