mikepricephoto

My A/C was diaged as needing the expansion valve replaced. It doesn't appear to be a difficult job but not a DIY. Has any other ML350 (166) owners had this repair done at an independent shop and what was the cost if you don't mind me asking- thanks!

SmokinJoe

I am a HVAC professional, a TXV is NOT a DIY job.
A shop that specializes in A/C should be fine. A dirty messy 1 man shop I'd avoid.
NOTE: get a price from your dealer, you may be surprised when comparing prices to competition.
Generally a TXV replacement involves a new valve, new refrigerant dryer / receiver, o-rings, recovery, evacuation, and recharge.

mikepricephoto

Thanks for your reply and professional advice- there any harm in not doing the repair as long as the a/c is blowing cold 90% of the time?

SmokinJoe

When does the a/c fail the 10% of the time? On hot start-up or running down the road at speed?
That doesn't sound like a bad TXV.
Did they reclaim and weigh in the proper refrigerant charge?
I don't want to diagnose via forums but if a TXV is clogged or failed it doesn't start to work unless there is moisture in the system (freezes). I've seem them overfeed, start cooling fine then die or just be dead period.
Inexperienced techs will just add refrigerant without observing the high side.
The sad part is by replacing the TXV they'll likely inadvertently solve the issue because the aforementioned would have to be done regardless.
That being said, I strongly caution against going to Walmart and buying a can of refrigerant.
Finally, to answer you question of damage, without going into detail, it's very possible to damage the compressor if the refrigerant flow is improper.

chassis

@SmokinJoe What is the risk of putting a can of Walmart refrigerant into the system?

SmokinJoe

LOL, blowing up the compressor internally, wrong refrigerant, hurting yourself.
Most kits don't have the hi-side hose and gauge and if there is a restriction you'll be operating WAY over the design head pressure. Most folks (even some certified auto mechanics) wouldn't even know what they reading on the gauges even if they had a full set.
Expensive car, have a pro do it the way I suggested.

chassis

Thanks @SmokinJoe . Are you an MB or auto tech?

SmokinJoe

You're welcome. No, I'm an Unlimited certified HVAC & Refrigeration Mechanical Contractor, Master Electrician and instructor since 1973. Please heed my advise, I can't tell you how many people have messed up their cars by trying internet DIY. I had my neighbor put 5 cans of the wrong refrigerant in the a/c of his Catamaran. Cost him $1400 just to get back to square one, only to find his water cooled condenser coil was fouled.

chassis

Thanks again, it’s good to have your experience on the site. R134A is the only automotive refrigerant in use these days, is this correct?