I have a mobile home with an Intertherm central HVAC system...all
electric. T-stat has two selector switches: mode (HEAT-OFF-COOL) and
blower (AUTO-ON)

I replaced the blower motor last summer..old one burned out after
blower wheel set screw came loose. After that, everything was working
fine...mode in "COOL" and blower in "AUTO".

Now, in the cold months, with the selector switch set to "HEAT" and the
fan control set in "AUTO", the heating elements come on but the blower
doesn't run. After about 5 seconds, the heating elements turn off then
about 5 seconds later the cycle repeats but still no blower. With the
blower selector in "ON", the heating elements cycle on and off
controlled by the T-stat while the blower runs constantly.

I really want auto-blower in both heat and cool mode.

Any suggestion?