Heater fans dont work

I knew the Heater Fans didnt work when I bought my 1995 P38 nine months ago. I was arrogant enough to think that I could fix them easily. However, after replacing the Fuseboard with a brand new one and changing all the relevent relays and fuses, also relacing the Hevac unit with a second hand one (from Emmotts) the fans still do not work.On one occasion a couple of weeks ago they started up and ran for about one minute then stopped.They havnt run since and I am running out of ideas.
The fact that the fans started up and ran for a minute suggests to me that the fan moters are ok.
The Display on the replacement Hevac unit works perfectly which makes me think that the Hevac is OK.
I read somewhere that the Hevac Unit and Fuseboard had to be linked to the BeCM with a T4. I didnt do this because of the cost of T4 services near me.Could this be the reason the Heater Fans are not responding to instructios from the Hevac?
Any Helpfull suggestions will be very welcome

No need to program the HEVAC to the BeCM - the only thing the BeCM cares about with regards to HEVAC is if you have the Climate Control or Manual version....

First thing to try is to disconnect the wiring plugs from the fan motors and make sure you are getting power to them, then run the fans from a 12V source to make sure the fans actually turn....

If the fans turn, but no power from the HEVAC time to recheck the fuses and relays and the interconnecting cabling....

get hold of RAVE for the schematics....

Had the same. Strip down the fans to the motors, vacuum out all the carbon dust from bushes and internals and hey presto works like a charm. Thought it was just luck but when i did the same on both fans any they both worked again it appeared to solve the problem. Worked for the last 18 months ever since. If bushes are knackered and really low get some cheapos and replace.

Edit; mine did exactly as yours did, ran up once then stopped. Heva was fine fuses and relays fine. Just removed motor bushes and hoovered the internals (lots of dust) and reassembled and tested on battery and was fine from there on out.