2001 Saab 9-3SE Conv-Heating-Cooling Issue

I have a 2001 Saab 9-3 SE Convertible that has the folowing problems with the heating and cooling system. The problem is intermittent-randomly happens-no pattern that that I can determine. This past winter we would put the heater on heat and even though the car was warmed up, the heater would blow cold air. We might stop for a cup of coffee and surprise, surprise, we had heat again. Two hours later no heat. Never knew if we were going to be comfortable or freeze on a cold day. Now it is summer and new problem. It's 90 degrees plus and no cold air. Now an hour later, we have cold air. I have tried to find info on this problem. Some say it could be something called a blend box. No one provides detailed information as to how to troubleshoot it or exactly where to find the blend box. Photos would be helpful. Any help would be appreciated as my fear is driving into a reapir shop and driving out needing a loan from the bank to cover the repairs. I would prefer to do the work myself if at all possible. The car seemed like a fair deal when I purchased it until I had had to fix it and it always seems to be above average cost to repair. I would appreciate your help.
Thanks,
Bob

I think I can help you with pictures and a how to.... if you still need it. Send me a PM if you need it. If not, I hope you got it working!

yes i got it is working nice to see it.

Well, I thought it was fixed when we replaced the entire control panel (the one that has all the controls and read outs). We actually changed out the panel twice. It pops out easily from watching the shop replace it. Unfortunately-it does not work and it is a puzzle to all the local Saab experts as they have not seen this problem. It is Summer, temps are 90's, and the car does not blow cold air. Winter, it is in the 20's and no warm air. Lately what has been happening to avoid a blast of warm air is we have turned everything off. But every time we start the car, it automatically goes to blower on high speed and the readout says LO. We have been spending a lot of dollars and not getting any closer to a fix. If you have the solution, we would really appreciate the help. We don't have boatloads of money and we would prefer to keep the car another 2 or 3 years rather than sell it broke. Pics would help if you have a solution. Thanks.

There must be an association between no heat at times in the winter and no cold air in the summer. I would think a sensor or control. We replaced the panel that has the controls in the dash. What might be next? I am thinking this is not a unique problem to my car and someone must have experienced it before.
Local Saab shop was not able to fix problem. Thanks, it really hot driving this car that normally we really enjoy.

Let's run down the list of what has been done.
Took the car to Saab repair shop. They did not fix AC/Heater.
Replaced the control panel in the dash twice. Did not fix problem.
Ran diagnostics on car using code reader. No fault codes.
Pressed Auto and Off on the control panel at same time and no codes showed up. Only a zero when first pressed.
What do I do next? 100 degrees tomorrow and blowing hot air even when set at 60 degrees. Very frustrating. Must be an answer. Any good AC folks reading the forum.
Thanks!