Jeep GC 95 Climate Control Code Problem

Hi folks - hope someone can help...

I've searched the web high and low to see the cause of this problem,
but whilst I see a few people have suffered the same plight - I don't
see any description of the problem and what can be done to cure it.

I have a 1995 JGC that has been a wonder, since it's still looking
great and going strong with 240K on the clock. There are issues popping
up here and there, most which I can live with or fix.

But now with summer coming to CA I have one I must fix.

The fan of the climate control system no longer pumps any air through
unless on the high setting - so unless it is on high, the fan is not
working at all (regardless of a/c setting). When turned to something
other than high the code ER appears in the LED where the temp would
normally be.

Cannot find anything in the book - and I've check fuses etc...

This was an intermittent problem for a while - now it's a full time
one.

I don't want to go to a dealer and have them try and sell me a new back
axle...

Anyone any ideas?

Any help most highly appreciated - I want this car to keep on going,
she's not ready for retirement yet!

Thanks.