Heat Blows Only Above 65MPH

[Fizzle]

So its Getting Cold Here In The Windy City And My Heat Doesn't Work Correctly. I Turned The Fan On Full Blast AAnd The Heat On "HI". The Air Just Comes Out Extremly Slow. But When I Get The Car Above 60-65mph The Its Like The Vents Have Opened Up And Out Comes The Air The Way its Suppsed To. I Live In The City, Nowhere Here is The Speed Limit 60mph, I'd Have To Drive To Indiana Just To Get Warm. Help Me PLEASE!!!

[Logic]

my c230 kompressor sport was doing something similar to that where the fan speeds didn't seem to work correctly. i don't know if this will fix your problem but it seemed that when i had my MAF sensor replaced it seem to be working fine after that... it could also be a vaccum issue also....just throwing some things out

[Markland556]

check the cabin air filter under the passanger side of the dash

[Proven Guilty]

i've never experienced this in the W202 yet, but i had this problem in my '90 chevy beretta in high school. replaced the heater core and thermostat, and all was well.

[V1Dreamer]

with your car on and heater on full blast. look in the engine bay, look for the lower radiator hose, not the main one. but the one that is a little smaller, about 1 1/2" in diameter.
follow that hose. it should take you up the passenger side of the engine bay and in through the dummy firewall.
there you will find it connected to your mono-valve. this is what controls the amount of heat going into your heater core.
so while your engine is running, take your mercedes benz special tool #5 (hammer or any blunt object) and give the mono-valve a few taps.
if you start getting heat out of the vents. you should change the mono-valve.

hope i was of assistance. let us know how it goes.

[V1Dreamer]

oh sorry, didnt read the part about the air not coming out of your vents. i thought it was just a heat problem.
but yea, check cabbin filters.

[Fizzle]

Dreamer, its air and heat. I'm mainly worried about the heat, I never use the ac. So if heat comes out of the vents who I tap the mono valve then I should replace it? How much do these run?Would the tapping test mean something is obstructing the flow?

[V1Dreamer]

yes your mono-valve controls how much coolant goes into your heater core.
the mono-valve is just a electrically controled piston. the internals of the monovalve are metal and plastic. the metal portion tends to rust, and the plastic tends to deteriorate.

but your concern about the volume of air coming out of your vents has nothing to do with the mono-valve.
the mono-valve only controls the temperature of the air.

[V1Dreamer]

im not sure how much they run, but im pretty sure they are under $100.

if you tap it and nothing happens, i suggest you take the electrical connector off the mono-valve and put 12v to it. you should hear and or feel it click.
if it does click, your problem is with whatever sends the 12v to the mono-valve.
if it does not click, replace it.

[Fizzle]

Ok So i Finally Go The Chance To Check And The Valve Was Ok. So i Then Checked The Cabin Filter And Noticed Another Compartment next To it And Opened It Up. It Was The Space For The Blower Motor, And It Was Not Blowing. So I Guess I Need A New One Or I'm Gonna Check The Voltage And My Current One. Do these Things Go Out Often?

[mbLova]

Originally posted by V1Dreamer
oh sorry, didnt read the part about the air not coming out of your vents. i thought it was just a heat problem.
but yea, check cabbin filters.

Maybe it's my body being whack, but I just got the car back from the stealership and turned the heat on. It seems like it's cold air to me. I switch on the defrost and BOOM I get really hot air. Maybe it seems cold as it's sunny outside and my car interior is black..
Any thoughts on this?

[strictlyspeakin]

Take a thermometer in with you. Maybe it is blowing at the temp you set if for, but it just seems cold?

[mbLova]

Originally posted by strictlyspeakin
Take a thermometer in with you. Maybe it is blowing at the temp you set if for, but it just seems cold?

Yeah it just turned out to be me.

[OzC36]

Fizzle,

If the blower motor is not blowing, ether the motor is stuffed or the blower motor regulator (Blower Motor Resistor/Regulator) has failed. Generally, it is more likely and fairly common for the blower motor regulator to fail rather than the motor itself.

I had to install a new regulator in my car recently for the same failure that you reported.

You can buy a new one on ebay or at Autohausaz dot com.

[Fizzle]

I started doing research on replacing my current one. As a college student i figured i'd do it myself. I took the panels off and exposed the motor. It was not turning by hand at first. I then twisted just a bit harder and a tiny twig fell out. I turned the heat on from the HVAC and it worked like a charm. I sprayed some wd-40 on it, closed it up, and haven't had a problem since. That was over a year ago.

[OzC36]

Heh! Heh!

I guess it pays to check the date-time group of the original posts!

Good to hear a simple fix to the problem.