RockCandy1013

I have a 2007 Merc R Class 320 CDI the heater will not work when the outside temp is under 35 deg.... The Air Conditioner wont work if its over 80 deg... any ideas? BTW its ben to Mercedes and the heat issue they think may be the heater core.... yet it blows heat just find over 35..... the car is awesome like new ….. but is a fair weather car at this point any help or suggestions would be greatly appreciated.

efzauner

HVAC is very complex. tons of sensors and controls. Dozens of pages in the service manual.
but: what wont work? there are many parts of HVAC.
Blower, ?
Hot/cold mixing?
hot coolant thru core? there are control valves!
AC compressor/refrigerant thru evaporator?
What exactly happens, shuts down when you exceed these temperatures? You are not describing much..

The common item may be the outside temperature sensor? . Did MB diagnose this?
Find where it is and see what happens when you cool or heat the sensor in a bath of water etc.

RockCandy1013

ok so yes I have taken it to Mercedes and they cant figure it out the issue even on their machines.... so the ac is goo the heater is good all is good unless its under 35 deg or over 75ish for A/C











Blower, ?...….blower is good


Hot/cold mixing?..... heat is good ...a/c is good again over 35 / and under 75


hot coolant thru core? possible at 1500 bucks to find out? …. maybe heater core... that may explain the heater to an extent but.....over 35 hotter then hell..... but does not explain the A/C


AC compressor/refrigerant thru evaporator? yes cold as ice until 75 to 80 deg reached them warm to Med hot


What exactly happens, shuts down when you exceed these temperatures? You are not describing much..... im sorry to be vague but this is what happens....


I am going to try the bath this weekend and also the pdf file test and update as I am done..... if there are other sensors in the car perhaps they need looked at also I just need to know where they are....locations of sensors would be great one last thing..... today I noticed when I had the heat on it blew nice until I made a left hand roundabout then it went warm to cool...… that's happened a couple of times..... so I tried the opposite.. and it got warmer..... hmmm blend door issue? but how would that explain the steady drive on highways when the ac turns off when the outside temp reaches 80...…. or in mornings when the heater dosent work at all till 35 deg... and in Colorado its been pretty damn cold at 6 am …...BRRR








Thank You for replying very much !!

efzauner

try the following
get a can of electronic cooling spray it is used to cool overheating parts. run your heating then spray it on the sensor.
Describe what happens. "stops working" is really insufficient. does the blower stop? does the blower continue but air cools down? Does entire system shut down instantly at 35F?

get a blow dryier.. do the same.. what happens at 85F?