Dear Forummers,
Need some help here.
My XK 4.2 NA (2007) aircon wasn't blowing cold air, and was told by the mechanic that I needed a new AC Compressor. So I checked out local sources but couldn't find any, and I decided to order from online sources after determining that the part number is C2C39502 (superseding C2C27255). The new Compressor arrived and I sent it to the workshop for replacement. When the existing Compressor was removed and compared with the new Compressor, we found out that the old compressor pulley's diameter is 120mm whilst the new was smaller at 115mm.
The mechanic isn't sure what to do. I'm not sure if this new compressor is right for my car. Has any forummer here changed their AC compressor before? ...and any used a smaller diameter pulley of 115mm?
Can the car's pulley tensioner tighten the belt sufficiently to run a smaller AC Compressor's pulley?
Perhaps, I can run the 115mm pulley but switch to a shorter belt (which should be around 16mm shorter based on the reduced circumference)?
Any suggestions and advice would be deeply appreciated.
Thanks in advance.

 

As long as you can actually get the shorter belt if needed it should be fine and if anything perform better at low RPM.

 

Thank you for the input. Let's see if i can find a 16mm shorter belt.
I'm hoping the tensioner will take-up the slack.
Will update once I find a solution for this.

 

My bet is it won't make a difference . It's 5/8" to us which shouldn't be a problem.

 

Always consider replacing the belt when replacing an alternator, compressor or water pump. Whatever, do check part numbers for the belt. If it is the same, then use the same belt. Otherwise, use the new part number belt.

 

I am going to question the premise that because the new compressor pulley is 5 mm shorter in diameter, therefore the belt should be 16 mm shorter. This might be true if the belt wrapped totally around the pulley. Since it actually does not do so, the change in the belt length would be proportionately less. For example if the belt wrapped around 50% of the pulley's diameter, then maybe the belt should be 8 mm shorter, etc. 8 mm is 1/3", and the belt tensioner should be able to take up that slack.

I also would encourage the OP to have a new serpentine belt installed.

 

Why didn't i think of that? The belt doesn't even wrap-over half the circumference of the Compressor's pulley. From technical visuals, it seems that the belt just slides over 45% of pulley's circumference in driving the compressor.
The original serpentine belt (Part #: C2C37063) is quoted at 2315mm in length (or generally known as 6PK2315). I reckon the tensioner should be able to take the slack. Else, i could just get a new slightly shorter 6PK2310 belt.
Thank you all for the great input.

 

 

Just an update for everyone:
Installed the new 115mm pulley AC Compressor last week, and everything is fine. Cold and no slack. The takeaway is any pulley size differences with just 5mm won't make a difference.