Just some info for the more adventurous of us. I recently had the not unknown problem of a heater motor continuously running at full chat. That was due the a failure of one of the internal amplifier transistors, these are getting difficult to find and becoming expensive. RS Component can supply a suitable alternative,
Stock number 688 1502. On Semi MJ11015G PNP Darlington transistor. They come in packs of 2 and currently are priced at £5.78 plus VAT and postage. Brilliant service - next day delivery. These are a direct replacement and are slightly over spec when compared with the original and so should last longer.
Hope that's helpful.

Good to see that forum members don't mind getting a little more technical!

RS is a good source for replacement semiconductor components but they may not always be able to provide a direct replacement but you can then source a similar device with higher spacifications - as I believe you have just done!

I have my interior completely removed so I may be an opportune time for me to check the operation of my HIVAC system, (going by the state of the rest of my vehicle I will be very surprised if it works)!