W124 ac suddenly blows hot - Page 2 - PeachParts Mercedes-Benz Forum

nulu · #16 06-19-2021, 07:08 PM

check the power wire to the compressor it may have broken off the lug, pull on it , my 94 just broke 2 weeks ago , just resoldered new wire

speednjay · #17 06-19-2021, 09:16 PM

Quote:

Originally Posted by ah-kay

Have you tried to measure the pressure on low and high pressure ports? You can also try to block hot water flow by clamping the hose going into the car. Touch the expansion pipe under the hood, is it cold? It is not difficult to diagnose AC.

It is not unusual for AC to fail suddenly. I have a compressor failed on me all of a sudden when the metal valve inside the compressor broke and jammed the unit. Luckily the kilma relay will kill the AC when it senses the shaft is not turning. Your problem doesn't seem to be the compressor. Good luck.

I haven’t checked pressures yet. Apparently I loaned out my ac manifold to my dad and now he can’t find it. I’m gonna try to take it to a shop Monday. It’s so hot outside to spend time diagnosising things

Touching the ac hard lines .. one is lava hot and the other is ambient temp. Ac compressor seems to turn on as normal from the climate control panel. Is there a switch or something that would block that line? Comparing it to my other w124 the line near the master cylinder should be cold.

Sugar Bear · #18 06-19-2021, 10:25 PM

Sounds like a blockage maybe in the expansion valve. The compressor is making pressure creating the heat, that is good. The refrigerant probably isn't getting into the evaporator where it expands and gets cold.

Probably shouldn't run the compressor until gauges are on it and the pressures are known.

If the refrigerant system is opened, insist on a new receiver drier, reusing it isn't an option IMO.

Good luck!!!

speednjay · #19 06-19-2021, 11:12 PM

Expansion valve.. sounds like fun

speednjay · #20 06-23-2021, 07:33 PM

Wife took car into the ac shop and they said that the high pressure side service valve is leaking and system had very little refrigerant left. I wasn’t to put gauges on for myself so I don’t have pressure numbers. Something doesn’t add up because the compressor engages/disengages as normal. If true maybe possible faulty pressure switch? Again the ac was ice cold working perfectly then in an instant blows hot.

ah-kay · #21 06-23-2021, 07:43 PM

Compressor runs doesn't mean it has enough refrigerant. It only takes 2.6bar for the switch to come on. In all likelihood it is lack of refrigerant. Spray some soapy water on the port to check. Best is to use the A/C gauge. You took it to the shop and you didn't authorize the repair?

speednjay · #22 06-23-2021, 07:57 PM

Quote:

Originally Posted by ah-kay

Compressor runs doesn't mean it has enough refrigerant. It only takes 2.6bar for the switch to come on. In all likelihood it is lack of refrigerant. Spray some soapy water on the port to check. Best is to use the A/C gauge. You took it to the shop and you didn't authorize the repair?

I told wife to go get the lines evacuated because I had to work. I totally would’ve got the valve repaired and recharged. I’m not too sure why she didn’t make that decision. As long as the thing is empty I’m gonna freshen up some of the parts before the weather gets back into the 100s

speednjay · #23 06-25-2021, 05:45 PM

Anyone have a part for the high pressure side service valve?

Wife took car to get valve replaced and they say they can’t get it. If they somehow can it’ll cost a lot because Mercedes

ah-kay · #24 06-25-2021, 06:32 PM

Quote:

Originally Posted by speednjay

Anyone have a part for the high pressure side service valve?

Wife took car to get valve replaced and they say they can’t get it. If they somehow can it’ll cost a lot because Mercedes

The repair shop cannot get the high pressure hose or the schrader valve? The valve is easy to replace, can be done without discharging the refrigerant if they have the special tool. Otherwise just discharge or recover the refrigerant. The valve is similar to a bicycle tire valve. May be take it to another shop.

speednjay · #25 06-25-2021, 08:25 PM

Quote:

Originally Posted by ah-kay

The repair shop cannot get the high pressure hose or the schrader valve? The valve is easy to replace, can be done without discharging the refrigerant if they have the special tool. Otherwise just discharge or recover the refrigerant. The valve is similar to a bicycle tire valve. May be take it to another shop.

Ya they tried to pull that stunt. Then all of a sudden they found the part. Fortunately she pays attention when I explain how stuff works on the car and wouldn’t let them take her for a ride

speednjay · #26 06-28-2021, 11:22 PM

Ok so now I got a new problem. Sometimes the ac compressor doesn’t get triggered when the car starts. If I shut the car off then restart then compressor works. Never had a problem like this till after the shop recharged the ac.

lsmalley · #27 07-06-2021, 04:52 AM

Quote:

Originally Posted by speednjay

Ok so now I got a new problem. Sometimes the ac compressor doesn’t get triggered when the car starts. If I shut the car off then restart then compressor works. Never had a problem like this till after the shop recharged the ac.

Seems like you're spending a great deal of time with back and forth on the a/c with the socal temps being as they are. If you have the time, you should personally take the car back to the shop. If not, then if you want a copy of the FSM a/c chapter for your car send me a PM. I think we've all been there at some point, I know I have and it's not fun. I usually try to do a/c tuning in the winter and heater tuning in the spring to avoid not having either when I need them.

speednjay · #28 07-06-2021, 09:12 PM

Quote:

Originally Posted by lsmalley

Seems like you're spending a great deal of time with back and forth on the a/c with the socal temps being as they are. If you have the time, you should personally take the car back to the shop. If not, then if you want a copy of the FSM a/c chapter for your car send me a PM. I think we've all been there at some point, I know I have and it's not fun. I usually try to do a/c tuning in the winter and heater tuning in the spring to avoid not having either when I need them.

So far the ac is back to normal for whatever reason. That shop was scamming everyone there. My girl knows the mechanics of how the ac works in the car and kept calling them on their **** when they thought they could get away with invoicing nonsense. I’m tempted to buy my own ac recovery and charging machine. This is Bakersfield it’s 100+ degrees for like 8 months out of the year. The ac just has to work.

panama74 · #29 09-15-2021, 11:46 AM

First off I am new to the forum and have limited mechanical capabilities. The most mechanical thing I have done was replace the thermostat on my 2011 C-350 and replaced the motorcycle battery (under spare tire)on my 2015 GLK. My current problem is with the a/c on my 2011 c-350 it blows cool but not cold then for no reason starts to blow cold. Dealer stated they thought it was a control module (ECM) but weren't 100% sure and the cost was in the neighborhood of $700-$900 to replace but no guarantee that it would correct my problem. Does any one have any suggestions, or has this ever happened to anyone else?

Thanks
Bill