Originally Posted by Nutmeg
Have an 07 f-53 with an intermittent squeal in the dash heater. Comes with heater on in any of the right hand positions, dash/floor or def. With fan on or off. Does not change pitch or volume with changes in fan speed. Stops immediately when you put selector in the straight up off position. Frequency is irregular every couple of minutes for a few seconds to 10 or 12.
Dash AC is also acting up gets cool for about 15 minutes then starts blowing warm. No squeal in AC mode.
Anyone had this before? Guess's what to look at?
How bout this guess? Since the squirrel cage motor with heat makes sound it could very well be a contact between the spinning rotor and the statioary housing. Heat causes expansion, which would cause a rub long before a cold rotor. Most fans are very close clearance to maintain the H20 pressure rise across the fan. If the slightest wear occurs in the overhung shaft bearings, contact will happen with heat before cold.
As for the A/C thats a bit more complex, could be expansion valve not staying open, low on refrig. Should have someone hook up gauges and give a more defined guess. The rub situ above can be verified by removing the suction hose and housing and inspect the rotor in place.