I'm having a problem with the wifes Montana...the temp control seems to have no effect...it just stays on full hot even if you turn the A/C on or dail it all the way down to cold...I picked up a Haynes manual but it has no info at all on where the heater control valve is located...does this sound like a control valve issue or a dash switch gone bad? The Haynes manual shows how to swap the dash control panel but nothing on where the cooling water is controlled...any help would be great...thanx in advance.