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Discussion Starter · #1 ·
Well just rolled over 100k a few days ago and it seems I have my first A/C failure. I've been lucky so far and haven't had any of the issues that the S550 A/C system seems to be plagued with. Yesterday on the way home from work it was finally warm enough that I wanted the A/C on, turned it on and nothing.... No sign of cold air, no slight rpm drop from the compressor engaging, no click sound of it turning on and just ambient temp air blowing through the vents.

Got home and popped the hood, had my gf sit in the car and cycle the A/C on and off to see if the compressor would try and engage and nada. The compressor pulley is being spun freely by the belt, not binding or making any odd noises that I could see or hear.

So I started with the simple thing, checked the fuse for the A/C in the fuse box a 10amp I believe and it was fine, swapped the A/C relay with the horn relay to make sure it wasn't blown and the horn still worked, so the relay is good.

The A/C worked flawlessly at the end of last summer and I don't think ive had it on since September, so I'm thinking its a sensor rather than the compressor has crapped out, since its not even engaging.

Any guys with A/C experience know which of the A/C sensors would cause the compressor not to engage? This is one area of the car I have no experience with.
 

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Discussion Starter · #3 ·
Low refrigerant in the system can also cause the compressor not to engage. Maybe a leak?
I read that, would R134 just evaporate if there was a leak? Cause I haven't had any leaks on the driveway since the last time I used it.

Was going to get the system pressure tested, but wanted to see if their were any cheap sensors to check first.
 

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I read that, would R134 just evaporate if there was a leak? Cause I haven't had any leaks on the driveway since the last time I used it.

Was going to get the system pressure tested, but wanted to see if their were any cheap sensors to check first.
Your refrigerant isn’t R134 unless your car is very early, all new cars are pretty much using yf1234 refrigerant, and that stuff is around $1k for a bottle.
 

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Discussion Starter · #6 ·
As KewlWinter said low refrigerant. But just to be sure it’s not dash controls, turn on defrost and see if the compressor engages.
I tried that as well, defrost was not making it engage either.

After a little research I came across something called the A/C clutch cycle switch? It seems if this goes bad the clutch will not engage. Possibility that this is it?
 

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Discussion Starter · #7 ·
Your refrigerant isn’t R134 unless your car is very early, all new cars are pretty much using yf1234 refrigerant, and that stuff is around $1k for a bottle.
There's no signs of any kind of fluid leak in the engine bay, and I checked the lines they all seemed fine. No cracks or tears that I could see, but I suppose only a pressure test will tell.
 

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Most times you won't see any evidence of a pinhole leak. That is why once they slap on the A/C gauges and see low pressure and no apparent evidence of leakage, either a dye or a sniffer is used to find it. Just hope if its a leak that it isn't in the evaporator.
 
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There's no signs of any kind of fluid leak in the engine bay, and I checked the lines they all seemed fine. No cracks or tears that I could see, but I suppose only a pressure test will tell.
The new refrigerant has a very small molecule and can leak in places you can not see by eye.......only reason I know that is having to attend a class for our new HVAC equipment here at the shop. The only evidence you may be able to see is a shinny spot “if” some of the compressor oil leaked also, the rest will evaporate.
 

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Your system is 5 years old. I don't know if/when your last A/C check-up was performed, but it is normal to have refrigerant losses over time. The first step to resolving your issue should be putting some gauges on the system to determine if that is the problem (KISS).
 
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Discussion Starter · #12 ·
The new refrigerant has a very small molecule and can leak in places you can not see by eye.......only reason I know that is having to attend a class for our new HVAC equipment here at the shop.
Good to know, thanks kent. I'll probably start with renting the pressure test kit and go from there.
 

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Good to know, thanks kent. I'll probably start with renting the pressure test kit and go from there.
Just put in an order for ACPro for $30 at Amazon. Even if you don't end up using it, you will sooner or later...and for $30...it ain't bad. ACPro has the best pressure gauge of all the handheld DIY refrigerants.
 

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Discussion Starter · #14 ·
Just put in an order for ACPro for $30 at Amazon. Even if you don't end up using it, you will sooner or later...and for $30...it ain't bad. ACPro has the best pressure gauge of all the handheld DIY refrigerants.
Will probably grab a bottle after I do the pressure test, I'd hate to try that and fill up the system just to have a leak or have another part that has failed.
 

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You n
Well just rolled over 100k a few days ago and it seems I have my first A/C failure. I've been lucky so far and haven't had any of the issues that the S550 A/C system seems to be plagued with. Yesterday on the way home from work it was finally warm enough that I wanted the A/C on, turned it on and nothing.... No sign of cold air, no slight rpm drop from the compressor engaging, no click sound of it turning on and just ambient temp air blowing through the vents.

Got home and popped the hood, had my gf sit in the car and cycle the A/C on and off to see if the compressor would try and engage and nada. The compressor pulley is being spun freely by the belt, not binding or making any odd noises that I could see or hear.

So I started with the simple thing, checked the fuse for the A/C in the fuse box a 10amp I believe and it was fine, swapped the A/C relay with the horn relay to make sure it wasn't blown and the horn still worked, so the relay is good.

The A/C worked flawlessly at the end of last summer and I don't think ive had it on since September, so I'm thinking its a sensor rather than the compressor has crapped out, since its not even engaging.

Any guys with A/C experience know which of the A/C sensors would cause the compressor not to engage? This is one area of the car I have no experience with.
You need to get a set of A/C gauges on the system to see if it has any pressure in it. My hunch is that it's empty, due to a leak. And you're not going to see a leak, as refrigerant is a gas at room temperature. If you have a big leak, you may see an oil stain around where the leak is. Speaking of that, it's probably worthwhile to inspect the condenser at the front of the car. Lots of times, they pick up a rock that pokes a hole in it. It's in front of the radiator and easy to check out. If you see an oil stain, you've found your leak! Do these few things and report back to us, please.
 

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Ford had a problem with the evaporators leaking in the dash I had mine replaced a year after I bought it also the system is a closed system and should not leak unless there’s a oring leaking or hole in condenser as someone stated etc good luck ?
 

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Well just rolled over 100k a few days ago and it seems I have my first A/C failure. I've been lucky so far and haven't had any of the issues that the S550 A/C system seems to be plagued with. Yesterday on the way home from work it was finally warm enough that I wanted the A/C on, turned it on and nothing.... No sign of cold air, no slight rpm drop from the compressor engaging, no click sound of it turning on and just ambient temp air blowing through the vents.

Got home and popped the hood, had my gf sit in the car and cycle the A/C on and off to see if the compressor would try and engage and nada. The compressor pulley is being spun freely by the belt, not binding or making any odd noises that I could see or hear.

So I started with the simple thing, checked the fuse for the A/C in the fuse box a 10amp I believe and it was fine, swapped the A/C relay with the horn relay to make sure it wasn't blown and the horn still worked, so the relay is good.

The A/C worked flawlessly at the end of last summer and I don't think ive had it on since September, so I'm thinking its a sensor rather than the compressor has crapped out, since its not even engaging.

Any guys with A/C experience know which of the A/C sensors would cause the compressor not to engage? This is one area of the car I have no experience with.
Could be mouse damage to the wiring
 
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