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Discussion Starter #1
Hi guys. Had my serpentine belt, idler pulley and tensioner pulley changed recently by Goodyear. Shortly afterwards, (2-3 weeks) I have developed a horrendous rattling coming from somewhere in front of engine ONLY when ac (or heater) is on. Also, clock and lights that read drive, park, reverse, etc. dim every now and then and go hack to full brightness for no reason at all. All new parts were from Napa, btw. I had 100k roughly on the clock so I had these things changed out as a preventative maintenance. Lastly, I can see the tensioner jump slightly when idling.
Thanks for any help. This is driving me bonkers as I don't want any more problems to continue to arise.
 

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Hey Danny:
I haven't seen this on my commander, but what you're describing is not uncommon for cars as they age. One of the peripherals that's part of the serpentine is failing. The tensioner "jumping" is the dead giveaway.
The fact that you are experiencing electrical symptoms would make me suspect first the alternator, though it's possible that the belt is slowing enough that you lose voltage, so it isn't certainly the alternator.

I would recommend you get a length of broom handle, or rubber hose and use it as a stethescope to try to find exactly where the sound is coming from. The rattle is most-likely a bearing going.

I would not assume that they belt replacement caused this. it's pretty hard to screw-up that procedure. The tension is set with the built-in tension on the tensioner, so they can't really over-tension.

Good luck; let us know what you find out!
 

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When you turn on heat, its possible for the AC to come on as well. If you're in recirculation mode or any of the defrost positions, the AC is automatically turned on. A failing AC system can definitely drag the motor down and even cause stalling of the engine (which also means the AC system could be suffering expensive damage). There is an electrical connector to the AC clutch (on the compressor, by the pulley on the serpentine belt), disconnect it, to disable the AC, see if you keep having the symptoms. If not, then likely your AC was at the root of it. If the symptoms continue, likely it is something else.

The electric disturbances would make you think its the alternator, but you should be getting an electric system warning light (the red battery light on the dash) if that was true. Just as likely, if a bad pulley or item on that accessory drive was dragging the engine and nearly stalling it, then that could cause the electrical disturbances as well. The AC clutch draws a lot of current, so again AC problems could be at the root of the electrical disturbances as well.
 

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Discussion Starter #4 (Edited)
Thanks guys. As soon as I get back home to my truck I will try to track this down like you've described. Earlier today I did get the alternator checked and they said that was fine. Also, no matter what setting I have it on.....ac, heater, defrost, mix, etc. the same thing happens: rattling only when blower is blowing. When it's OFF, the tensioner is very still and all is quiet. The second I turn the knob (blower), no matter the setting, the rattle starts and the tensioner starts acting up.
 

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Discussion Starter #5
Guys....thanks for all the help. Turns out it was the tensioner pulley. Yes, the brand new one from napa. The hose trick worked and I narrowed it to that. I hadn't thrown the old one away so I put it back on and no more rattle (although it was old and not smooth) I took the new pulley back to napa and exchanged it for the whole tensioner assembly (better safe than sorry) and now all is well. Appreciate the help!
 
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