The dual zone climate control in my 2000 convertible with 58,000 miles is having issues with setting the temperature. Of course it is not the well known dim display issue, no problems there! When I turn the Driver's temp set **** while the car is running, the EXT temp continues to display and SET temp will not display or change. But when I try it with the ignition on and the car not running, the EXT temp display changes to SET temp and it will change as it should. The car still heats or cools as it should to the temp it is set to, the fan speeds are good, and the air flow locations change as they should.

Previously, I was having an intermittent problem where I could only change the SET temp 1 degree up or down, then had to wait until EXT temp displayed again, and go back to SET for another 1 degree. But now it has turned into this and seems to be consistent. The battery is near new and is kept on a Battery Tender whenever it isn't driven for more than a week.

Also, the Off, Auto, and Front Defrost buttons occasionally don't work while it's running, but seem to be OK when it's not running. I did check for diagnostic codes, there weren't any. Because it acts differently when the car is running vs. key on and not running, I'm thinking it might possibly be voltage or amperage related? Were there other soldering issues in these units not related to the dim display problem that I could look into?

I haven't been able to find any posts dealing with anything like this on the forum, any ideas??

Or does anyone have a NOS or good used unit they want to sell?

 

Reads like your idea of trying a different control unit is a good one. I don’t know whether it matters, but 97, 98, & 99 originally had single year part numbers. 00 through at least 02 originally had a 10436062 unit. Spares have become quite hard to find. Perhaps someone local to you will volunteer a quick loan!

 

Thanks redzg! From what I have read so far, I think they are all interchangeable, but I'm not positive. Anyone in the Denver metro area with an extra that I could try or buy? I'll also have to ask other C5 owners at the car shows that are starting up this month.

 

My 99 doesn’t work the way I expect, so I’m slowly working at understanding the blower control. In addition to four different control module part numbers, there are at least three different fan motor part numbers — but between those control modules and fan motors all years use the same blower motor control module. One part number to spin them all.
Lends credit to the idea that the control modules should be pretty interchangeable.