hi gurus

I have another problem. I have a mercedes 190 E 1993, The heater seems to blow out warm air at its lowest setting and gradually cooler air as i increase the fan speed. dial seem to work correctly but i am unable to get sufficient hot air to make the ride confortable in cold conditions. i have tried flushing out the system by attaching a powered jet hose to the heater inlet but that has not solved the problem. there are no water leaks, just cant get enough hot air to heat up the car on cold days. any ideas??

dean

 

check the mono or duo valve

 

I agree check the mono or duo valve, however there is a relay that controls the outside air intake and mixture. I have the same issue on my 560SEL at highway speeds at fan speed low I get very little warm air. The repair shop I use said it is usually one of the relays inside the dash. I have not located and changed mine yet to see if that is the problem.

 

My 190 is a 1989 and like yours the heater is pretty useless except in a traffic jam with the fan on very low. Like you I have flushed the system and checked the valve operation. My conclusion is that the heater matrix is pretty much blocked up. My reasoning is that I fitted a new water pump about 4 years ago and had to use some barrs leaks in order to get the backplate joint to stop leaking. A new matrix is relatively cheap at about £45 from G and S, but fitting it this weather will break about every plastic clip you touch, especially on an old car. Wait till summer like i did last year, then you wont need the heater and probably wont be bothered about changingthe matrixeither. The water pump and this heater problem are the only things that have failed in the 15 years and 150K miles I have had the car, so it's not all bad.

 

Simple way to check heater core (matrix). Locate the feed supply and return to it. Once vehicle is completely warmed up and heat controls on fullif one hose is warm and the other cold the heater core is blocked or supply valve is bad, valve can be checked the same way.

 

apologies for my ignorance but where is the mono / duo valve located? can it be accesed from the engine compartment? i have an hayes manual and have found it pretty useless. info or image of system is appreciated.


dean
happy new year to all and thanks for replies.

 

replaced heater or duo valve still have problem... how does the heater valve work? what makes it shut?? the in/out hoses of the heater unit are hot ... what's going on?

help appreciated..
deam