I will quote someone from another forum:

That's because later cars don't have a relay on the blower supply wire so newer IHKA won't send a signal to activate that relay in older cars. Also the AC compressor won't work since newer cars use 1 wire to communicate with engine ECU and older cars use 3 wires. To make blower work, you can remove pin 14 from the blue connector in IHKA and connect it to the wire that goes to pin 1. Pin 14 is responsible for activating this relay. After that, the blower should work, but most likely the air conditioning compressor will still not work.
However, there is a better solution. All you have to do to make everything work is to recode IHKA with DIS (it must be DIS, not NCS Expert etc.). I'm not sure if it will work with all IHKAs and cars but I have successfully fitted '99 IHKA to '96 car using this method.

The way my module failed is that I broke it. The buttons started falling out and were cracking. I tried gluing them, then I couldn't press them anymore. I took the IHKA module apart, and instantly regretted it. It was a huge mess. Took me a few hours to learn how to put it back together. Then I was playing around with it in the car while it was apart and was connecting it and touched something on the board that wasn't supposed to be touch, and I smelled something burned on the module lol....

So I got a couple of used modules, but they don't work. Basically the fan speed is not working. No matter how fast I set the fan, it doesn't blow any air.
I tried coding with NCS Expert and it coded fine, but it didn't fix the issue.