Gem Heater fan blowing, relay clicks, no heat

I have 2002, 12 volt heater, need trouble shooting guide to pinpoint problem. 15 amp and 10 amp fuses good. Element circuit in unit is not open. Gem manual states heater and radio are optional, no more info except part list. Unit is 0107-00587. Thank you in advance.

Not sure on the 02, but on my '14 there is a fuse mounted to the frame between the heater and the steering column, it was blown.

“Gem Heater fan blowing, relay clicks, no heat”:
from that description it sounds like the heating coils are broken since those sound like what should happen except the “no heat” and you know the heat is made from electricity flowing through heating elements and that is being turned on by the relay. So find the heater, disconnect one wire and measure the two connections on the heater for resistance. Should be only a few ohms. If open circuit the heater needs replacing.