How to install blower motor relays??

If you really want to do relays, then you will need one for each speed.
The resisted speeds still draw the same amps at the switch it's just that the resistor uses some of the amp so the motor runs slower.

This means that each wire off the back of the switch would need it own relay, and then the resistors would still function as they do now.
But the switch would be under way less of a load (like you are asking about)

I drew a diagram for someone on here just awhile back, so let me see if I can find it.


Here it is.
This was for a two speed blower, so if you have a 3 speed just add another relay for the third speed wired the exact same way.