need some advice. got a 97 pacearrow last yr. low miles. good shape. last winter used it couple wks.. in cold weather, furnaces in front and rear failed to ignite couple of times. i turned them off and reset thermostat and they would come on and heat fine. myself and girlfriend are retired and rving full time this yr.. the weather is getting colder and have been using both furnaces for a few wks.. the rear one works fine but, the front unit quit the other day. it just blows cold air. any suggestions. the thermostat control is in rear bedroom and has front and rear controls in one unit, controls fan, ac, heat, etc. thanks, mike