Heater blower will not turn off

I have a 1998 Plymouth Voyager that my wife and daughter usually drive.
Last week they told me that the heater blower only worked on high and
had been that way for a while.

So ... replaced the blower resistor .. no problem, wires were in good
shape so did not have to touch those. NOW ... the blower runs
constantly at one reduced speed except when at the high setting. The
blower will not turn off at all.

Is this a blower relay problem? (I tapped on the relay but with no
success). It seems strange that this problem would happen in parallel
with the resistor problem but I can't see how they are connected.

Thanks for any advice.