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A/C Pulley

2738 Views 10 Replies 4 Participants Last post by  TeflonVixen
I have a 99 E320 4Matic with 182k miles

Little background info, I had an A/C evac/recharge in April. About a month ago my blower motor or regulator went. Haven't figured out which one yet. Last week the idler pulley decided it wanted to snap in half as I was driving to dinner. In the process of it snapping it also shredded the serpentine belt. That was really fun. I fixed that this past Sunday however I am still hearing a rattling sound and another sound I can only describe as sucking air kind of.

I popped the hood and took a listen while it was running. I'm pretty sure the sound is coming from the A/C pulley. Since I have never taken a look at it prior to this, I am not sure whether or not the whole front should be spinning or not as it spins intermittently. Is it supposed to do this? Also, it appears pretty old and I'm sure the previous owner didn't replace it so I'm considering doing so. I guess I just wanted other opinions as I'm only a mechanic through this forum and youtube.


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I have a slightly different opinion. The MB A/C system is always engaged unless turned off by the EC switch or by failure of the system. This is different than many domestic systems which do cycle the compressor on/off.
Your serpentine belt failure may have damaged the electric connection for the clutch on the front of the compressor. I'd check this first.
The clutch can be purchased separately.
If you decide to replace the compressor, I agree with the previous post on brand.

Sent from phone.
My experience with the tensioner is documented. The bottom line was that the old tensioner was 1/2 of the new in terms of the effort required to rotate it to accept the belt.
All looked OK, but I was having belt slippage and the evidence was burned rubber smell.
If I recall coreectly, the old tensioner required 25Ft lbs to rotate it and the new was double that. A non-scientific report, but you get the gist. No problems since.
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