How many of you have had problems with the heater control not working properly? My moms car (91 SE) wont change from cold to hot... the knob turns, but hard... and the heat never gets hot. I manually switched the valve under the hood to turn the hot water on to the heater core, but still no heat... I hope the heater core isnt bad.

In my 5th gen, its picky... Sometimes it works, sometimes it dosent... sometimes the knob wont turn at all... and other times its fine...

What are your experiences with this? Ive heard of just changing the temperature control cable...?? is there one or two of these?