i am posting here because im curious as to what the cause of this is. on Saturday i was driving and all of a sudden the ranger belt chirped real loud and stalled out. since then every time i idle with the heater on the truck squeals like its about to come off. if i turn it off at idle and wait til take of it does not do it. almost reminds me of trying to run the a/c with a bad a/c compressor. i dont know what it could be and id like to fix the issue because im not the kind of person to have anything half done on a truck . any input would be extremely helpful. thanks

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1995 ford ranger 2.5l ive owned it for about 2 weeks. not my first ranger however my first one with 8 spark plugs on a 4 cylinder. since buying it ive had to do some for to it. new plugs and wires and todays task is replacing the egr value tube and o 2 sensors. still learning more about this truck every day

If you suspect the serpenteen belt, remove it and hand test the idlers and other pulleys for binding, they all should turn freely with your fingers.

If you have a tensioner on your serpentine belt, it could be that either the tensioner is losing its ability to keep the belt properly tight, and the belt is slipping, or the belt itself could be damaged.
If the noise is worse when you rev up the engine, but quiet once the engine has reached a steady speed, it is likely the belt is slipping.
The heater blower motor adds electrical load, causing the alternator to have to work harder. If the noise can be influenced by the blower motor, then the alternator may be slipping, but the cause of the slippage could be tensioner, damaged belt, or liquid/grease/etc on the belt or pulleys.
tom

What setting are you running the heat on, many settings (such as face and floor) run the A/C compressor so the noise may be exactly what you think.

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Baby Girl: 2006 White Ranger XL with many memories. R.I.P. 1/26/15