ticking noise thru radio ignition/plug wires?

[98trck]

sometimes I hear ticking noise thru radio, thought it was a plug wire.
been having problems with vent a/c fan not working correctly.
running slow, sometimes not at all.
one of the times it was acting up I turned off the fan.
and realized the ticking noise stopped.
turned the fan back on, ticking noise again was there.
turned fan speed up and the noise stopped.
wow what a relief its not the plug wires..
hope this will help other truck owners.
PETE