Ibiza heating system porch 92

I'm restoring a 1992 Seat Ibiza. It has heating and air conditioning.
The heating isn't working, and when I contacted Seat, their workshop manuals don't mention it, but I'm sure it has it because it worked the first month I had it.
Could anyone help me?
I found a relay with a double coil under the radio, and it was black. I took it to Seat, and they lost it. Could that be the problem? It's a 1.5 90hp five-door model.