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Does the A/C conduit get hot or cold.... could be bad blending door module
It is strange actually if I turn off the a/c I get somewhat cold air, I mentioned somewhat is because it is not cold air at all but just colder than the air from outside. If I turn on the a/c, the air is warmer than when I have it off, and the air feels more like the air from outside. I checked with the scanner and the button is functioning correctly, as in closing and opening the magnetic clutch and calling for a/c correctly. So I am not sure what happened. I mean, even with a/c off with the colder air, it can't really be considered a/c, the temperature is set to LO, system airflow, direction, speed all set to auto when I test this, it immediately blast the blower motor to max.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
The Schrader-type valves on the high and low ports could be a source of leaks and it won't be visibly apparent. Low refrigerant can cause the evaporator to freeze up (literally). To much pressure can cause the compressor to turn off (safety issue). Sounds like time for a trip to Harbor Freight (or Canadian equivalent or Amazon) for a set of HVAC gauges. The proper way to diagnose an a/c problem is reading the high and low-side pressures.
The Schrader-type valves on the high and low ports could be a source of leaks and it won't be visibly apparent. Low refrigerant can cause the evaporator to freeze up (literally). To much pressure can cause the compressor to turn off (safety issue). Sounds like time for a trip to Harbor Freight (or Canadian equivalent or Amazon) for a set of HVAC gauges. The proper way to diagnose an a/c problem is reading the high and low-side pressures.
That turn knob is to recharge refrigerant. I think I am starting to know what happened, I recall messing with this last year curious what it is, maybe I left the cap loose and the refrigerant leaked out. Thanks both for your help.
Yes, that is where you recharge refrigerant I figured, I probably left the cap loose last time and it evaporated?
Do you think I still need the full set of professional hvac measuring tools or simply a recharge can with a meter, if so which one do you recommend? Or what is the oem part number by chance? Thank you : )
Last edited by W205C43PFL; May 7, 2025 at 07:19 PM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Those are just caps and the Schrader valves are beneath. Not sure which is the high side and which is the low side, but they are different sizes and the gauges can only connect to the correct line. Here are the caps on my C350 and SL400. On other cars, the caps are sometimes blue and red.
Those are just caps and the Schrader valves are beneath. Not sure which is the high side and which is the low side, but they are different sizes and the gauges can only connect to the correct line. Here are the caps on my C350 and SL400. On other cars, the caps are sometimes blue and red.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by W205C43PFL
One thing that is also still not clear to me is why is the air temperature coming from the vents lower when a/c is off opposed to when a/c is on.
Does the air get colder immediately? Or after a few minutes?
Also, futzing around with the caps doesn't hurt anything. I think they are there to keep dust and dirt out of the valve, not to hold pressure. You may do well to take the car to an A/C specialist if you don't want to mess with it. If any repairs are needed, you need to go to a shop anyway because they collect the refrigerant with special equipment. In the US, it's a violation of federal law to vent the refrigerant to the atmosphere. Plus, you don't want to inadvertantly breathe a lot of that stuff.
Does the air get colder immediately? Or after a few minutes?
Also, futzing around with the caps doesn't hurt anything. I think they are there to keep dust and dirt out of the valve, not to hold pressure. You may do well to take the car to an A/C specialist if you don't want to mess with it. If any repairs are needed, you need to go to a shop anyway because they collect the refrigerant with special equipment. In the US, it's a violation of federal law to vent the refrigerant to the atmosphere. Plus, you don't want to inadvertantly breathe a lot of that stuff.
Solid advice, I see, if it wasn't the cap then maybe I do have a leak just can't find it. Thank you I might have to bite the bullet and go somewhere to get it fixed. I really hate leaving the vehicle overnight or away from me though. Reason why I like to diy but this is something I shouldn't diy I guess.
So is it possible for the refrigerant to slowly leak if I left a cap loose? Or it can only leak through a crack in a hose or something
If the Schrader vavle is leaking, the cap only slows the leak, it won't stop the leak. I had to replace the valve on my 2000 Ford F150 last year because it had begun to leak. They are like the valve on a car tire or bicycle tire. The valves are replaceable. The problem is that you have to evacuate the system and capture the gas. The after repairs, you need to run a vacuum pump for quite a while to evacuate the system of any air that got in. Once that is done, you then add exactly the amount or R134a that is specified on the sticker in the engine compartment. If you don't want to invest in all the equipment you'll need, then taking to an A/C specialist is the way to go. AND, the problem may be something else. If you want to know for sure, you can get some dye to add into the system and then use a UV light to look for any leaks. Most auto parts stores or Walmart or Amazon have the dye leak detector kits.
If the Schrader vavle is leaking, the cap only slows the leak, it won't stop the leak. I had to replace the valve on my 2000 Ford F150 last year because it had begun to leak. They are like the valve on a car tire or bicycle tire. The valves are replaceable. The problem is that you have to evacuate the system and capture the gas. The after repairs, you need to run a vacuum pump for quite a while to evacuate the system of any air that got in. Once that is done, you then add exactly the amount or R134a that is specified on the sticker in the engine compartment. If you don't want to invest in all the equipment you'll need, then taking to an A/C specialist is the way to go. AND, the problem may be something else. If you want to know for sure, you can get some dye to add into the system and then use a UV light to look for any leaks. Most auto parts stores or Walmart or Amazon have the dye leak detector kits.
Thanks for the tip, guess I have some researching to do tonight.
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