urbamworm

About a week ago I got in the car and it was blowing hot, I went in to a store and came back out and it worked fine. A good 5 days have passed and it has been working fine.

Today it was blowing hot again, I drove about 35 miles and it never worked, I shut it off and back on by the a/c button 5 or 6 times and no dice. Got out of car to get gas but it still didn't work after starting car back up like it did the week before. Drove another 40 miles or so with it not working and again hitting a/c button to off and on but no help. Went in to a store and came back out and it is blowing cold again.

It doesn't make sense to me to be a low Freon problem so I am thinking some kind of switch that is intermittently working? I am not an a/c guru but does this sound like an accurate problem? Trying to search on my phone but not finding what I need (same problem).

I looked up air conditioning cutoff switch or something like that on advance auto parts website, no clue where this switch is located or if this is the problem, so what do you guys think?

cij911

Have you checked the pressure of the system ? It is relatively easy and if the AC is low it could be causing the compressor to cut off. I tested my system last year (it was not really cold) and it was low on Freon.

urbamworm

I am traveling, haven't done any testing
But like I said, it has been working for a week perfect after the one mishap, that is why it just doesn't seem like Freon being low. Guess you never know but with the way it has acted up once a week ago then today and now perfect again at the moment it seems like something else.

I think I remember reading about a way to go in to controls of a/c in the car for a readout of how many bar of freon pressure or something like that. I will check on it once at my computer computer to see if I can look up that way just to be sure of the amount being correct.

need4spd

Not sure if it applies here but I had a similar problem on my ford truck and it turned out to be clutch adjustment on the ac compressor

Yacht Master

David, dose your car have a rest button on the A/C control head?
If so you can pull up the diagnostics for the Climate control system.

urbamworm

Hey Bob, will make a thread when I get home about last night but snagged Elliot's alternator today and it did the trick.

My My car is an 05 and I don't see a button like that. Assuming it is where there is a blank button to the left of the lower fan speed button?

urbamworm

Oh and just got out to go in another store and back in car again and it is still working perfect.

Yacht Master

Good deal on the alt
Ya I dont remember the trick for the newer cars that dont have the rest button, but there is a way to do it and also get fault codes in the AC too.

here is a little more info,

https://mbworld.org/forums/mercedes-...diag-mode.html

Denroll

Now that it is working, I recommend you stop going into stores, lol.

moosejaw

I use to have this prob in my C32 all the time until i got on the highway and it would finally turn on.
One day i read where someone turned their heater on full blast for a few minutes
I tried this and it did the trick. My AC came on full blast.

pimpjuice

Mine did this...it is a pain in the *** to fix. There is a heater control valve located under the hood cowl where the wiper motor and arms attach. I had to change mine out a few months ago. if you have huge hands be prepared to curse a lot and have battle scars. The part is relatively inexpensive, but it fixed me right up. Do all of your vents blow cold or just a few of them? Mine was intermittent like yours, I could have cold air in th eback seats but Hades hot in the front or just all hot. it was crazy. let me search a bit and see where the post is...its in here somewhere.

pimpjuice

Here ya go bro...this may or not be the culprit...if it is...here's the write-up

https://mbworld.org/forums/e-class-w211/250487-diy-installing-new-changeover-heater-control-valve.html

Shifter

Sounds like you need a proper diag via your local mb pros

urbamworm

Cool, I will check in to it. Got in the car this morning and it wasn't working again. I hit the "off" button then back on and it started working. Hadn't tried that yet when it wasn't working before, I was just hitting the "a/c" button and that didn't help.

It must be that dang valve. I have small hands so I guess that will help out. I haven't noticed different vents blowing different temps though, it was just hot.

Today it has done it twice more but by simply hitting off then off again to turn it back on it would start blowing cold.

NEED a/c right now, it is hot as a **** in south Florida.

urbamworm

Local in Key West?

Alps

i think pimpjuice has solved this for you, i had the same issue on mine, heater exchange control motor, some still call it the duovalve even tho its not that but performs the same function.

pimpjuice

I have star but im in northwest fl

Yacht Master

http://www.mercedestechstore.com/pdf...%208-30-02.pdf

I'll look around for the procedure to get in to the On Board Diagnostics. You can guess all day and throw big $$$$ at it and still never find the on /off problem.
There are 2 diag systems, one gives all the sensor values and the other gives fault codes.
You don't need star or a dealer to do this, it is so easy and finds the problem quick.

Shifter

My bad, thought you were in Jax

pimpjuice

Do a simple test of seeing if the different vents are all blowing hot air. If some are freezing cold and some are hot, 95% chance it the control valve. If they are ALL hot then that percentage drops considerably

BlackOmega

There's also a temperature sensor on the evaporator. Sometimes these things will freeze up and send the wrong signal to the computer. Other times the resistor itself fries and sends an irrational value to the computer and it thinks it's hotter or colder than it really is and hence your temperature output may be all over the place.

A quick easy test to see if your compressor is working properly, turn on the windshield defogger. This turns the A/C system on also. Locate the A/C compressor, on the W210's it's on the drivers side towards the bottom. If the compressor is locked and turning then it's on. If it clicks on then off then on then off, it's low on refrigerant (it's NOT Freon).

E55Greasemonkey

Our compressors don't have a clutch...they run all the time with variable output

EezyBake

I've been having issues with my rear vents blowing hot! the fronts work fine, but the rears blow hot, then I would put the rear temp up, then back down to low, then it would work sometimes. Im in AZ and this **** sucks bc the back of you just gets hot even though the front blows cold. Is there a proper name or pic for that valve under the wiper area that should be replaced?