300se heater problems
 

My 89 300se has just had the regulator replaced a couple of months ago and man, the ac blows now. Today I noticed it might be getting a little cool in the mornings the next few days and I checked the heat. Now, the air blows through the vents good, but the air is cool and not hot. Can this be the monovalve or the temperature sensor or maybe something else? Can anyone help?
Last winter I had the brushes replaced in the blower motor and the MB mechanic stated that the armature was in good shape.

Hydro-lock of mono heater valve is the most common problem.

heater problems
 

Hydro-lock of the monovalve...how does this happen and do you fix it by replacing the monovalve with the rebuild kits?

Scott

Scott
Release pressure in the cooling system by removing the cap, then reinstall
Remove the 4 screws fron the top of the watervalve, and pull out the insert by pulling up on the center of the magnet (the silver "knob" on top. (Oh, remove the wiring connector first).
Examine the part you just removed, on the underside. It's not the small central rubber seal that goes bad, but the diaphragm under the center seal. Pull out slightly on the center seal and look for any rips or holes in that larger rubber bellows or diaphragm.

Gilly

HEATER PROBLEMS
 

Is this normally what causes the heater to quit heating? Is there anything else that it might be? I did check the monovalve last winter and it seems fine at that point, but I do realize that age can cause these things to get brittle and rip or tear. Any suggestions?

300 SE HEATER PROBLEMS
 

Just wanted to let you know that I had the heater monovalve checked and it was indeed collapsed. I replaced it and voila, there is heat again. Thanks for all the help.

SCOTTFISH

glad to hear it was fixed. What was the cost of the part and which part did you replace?

Haasman

300 SE HEATER
 

I replaced the monovalve with the kit. I priced it online and the best price was $30 and come change at www.importec.com , but to get it in here by the next day, I would have had to pay bigger amounts on overnite shipping. I went to my local dealer and they had one for $44 and some change. My old monovalve diaphragm was completely busted. It is fixed. I did have a friend at a shop trouble shoot it and do the actual replacement. He charged me $40. That still was not bad considering it could have been something else that would have cost a lot more.