I have a problem with my Mercedes-Benz, I can’t figure out …. I close the Hvac blend door and the car still blow cold air now in the winter,, I am in ny. I put enough anti freez in it….. the AC over the summer blow cold air for a little while after I add freeon I bleed the air out but it goes back to hot over the summer
One of the first things you will want to do is to feel the two heater hoses that connect to the heater core once the engine has had time to warm up to operating temperature. This will allow you to know a couple of things. If both hoses are hot, the thermostat is opening and the heater core is not clogged. If only one hose is hot, then the heater core is clogged. If neither of the hoses are hot, the thermostat is not opening.
This is assuming that the coolant level is full and there are no coolant leaks present.
COOLANT DRAIN, FLUSH & REFILL
Warning: Risk of death caused by vehicle slipping or toppling off of the lifting platform.
Warning: Risk of injury to skin and eyes caused by scalding from contact with hot coolant spray.
Risk of poisoning if coolant is swallowed.
- Open engine hood.
- Disconnect battery ground.
- Open cooling system cap at coolant expansion reservoir.
- Raise vehicle.
- Remove lower engine compartment paneling.
- Remove under ride guard.
- Remove air deflector shield.
- Push siphon hose onto radiator drain plug.
- Open radiator drain plug and drain coolant.
- Tighten radiator drain plug and disconnect drain hose from radiator drain plug.
- Push siphon hose onto crankcase drain plug.
- Open crankcase drain plug and drain coolant.
- Flush cooling system with clean, drinkable water.
- Tighten crankcase drain plug and disconnect drain hose from crankcase drain plug.
- Lower vehicle.
- Pour in coolant and bleed cooling system.
- Inspect cooling system for leaks.
- Install air baffle plate.
- Install under ride guard.
- Install lower engine compartment paneling.
- Connect battery ground cable.
- Perform basic programming.
- Read out and erase the fault memory using Star Diagnosis or equivalent.
- Close engine hood.
Hello . I check the hose both are hot and the heat is very low , but it change on it own,1minute it’s low heat then ice cold ,,, I noticed that when I am on the highway, the heat a little better,, I thought that the engine heat.coming Thur the vent…. the aux pump has anything to do with it … i Change it about 4 yers who… it seem fine … is there a second Hvac been door that I miss … I don’t understand the heating system… there no radiator cap , there no leak ,the blend door broke . I close it Thur the glove compartment,,the blower motor work ok, the resistor work ok..,,, the thermostat is ok going by the 2 hose being hot the heater core is not clog…. the heater control could that go bad,, that control the Hvac blend in the dash board… I press the subscribe button for you tube…..
This seems to be a Blend Door Motor problem that occurs when the seasons change. That would mean replacing the blend door motor/actuator. I see you stated that you closed it through the glove compartment which should allow it to work temporarily. Not certain why it isn’t for you.
If you have a HOT heater core and then blow air across it there should be HOT air coming out as long as the pathway(blend door) is not closed/blocked.
I researched this a bit and found that you need to turn the climate dial all the way to HOT, which will probably do nothing but allow you to manually move the white plastic lever to the opposite direction switching it from cold to hot. If you found the lever loose then the door or motor may be damaged and not allowing it to remain in the right position.
Found a good article on replacing the blend door motor here: https://www.benzworld.org/threads/diy-thread-collection.1417771/page-3#post-4763314 when reviewing the original article here: https://www.benzworld.org/threads/no-heat-cabin-heater-wont-get-warm.1674846/
To properly replace the Blend Door Actuator/Motor and /or its levers, the following procedure should be followed.
This procedure eliminates the breaking of the tabs on the passenger side air bag deployment door and also eliminates the removal of the air bag. Only the top half of the instrument panel needs to be removed.
Also before starting, make sure that you have your radio code.
1. Remove left and right “A” pillar trim panels.
2. Remove upper and lower covers on steering column (3 screws).
3. Remove Instrument Cluster.
4. Remove center section of instrument panel (with plastic pry tools).
5. Remove radio (with keys).
6. Remove glove box
7. Remove defroster vent strip (with plastic pry tools).
8. Remove items, 6-7-9 if so equipped (with plastic pry tools)
9. Remove side panels #128
Start by removing those screws indicated in red.
Pull the ends and the top of the lower portion of the instrument panel slightly away to reveal the two green screws.
The two screws are upward inside that cavity. Feel around inside and locate them by hand or use a small mirror.
Then remove the two screws indicated in green.
Those screws indicated in purple might or might not be there, depending on model year.
Then gently pull away the top portion of the instrument panel, all the time making sure that every screw has been removed.
After installing the new Blend Door Motor and before replacing the Instrument Panel, reattach the A/C-Heater Controller, start the truck and check the workings of the Blend Door in every temperature stage.
On re-installation, it might be easier to fit the upper dash if the end and middle A/C vent were removed. If so, remove them by unlocking them from the back side.
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