1990 Suburban 4x4 1/2 tonne. 350

Hi.

I'm pretty sure I need a new heater blower relay, but wanted to run it by someone else (who knows more than me) before buying one.

The facts :

When I switch the heater on from inside, the blower motor does nothing.
When I run a hot wire from the battery to the blower motor, it fires up.
I'm getting 12v at the red wire that goes into the relay.
I'm getting less than 1v coming out of the purple wire from the relay that plugs into the blower motor ....

What do you think? Relay? or something else that I've missed?

Thanks,

Ross.