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+--- Thread: Heater problems (/showthread.php?tid=4132)
Heater problems - jandamerc - 11-29-2012
Hi all,
I'm getting highly frustrated with this ignorant ass heater system mercedes put in these cars. Its cold out and wife and kid ride in this car and I cannot get the heat to stay warm. It is only warm at idle. I have rebuilt the monovalve. Checked all hoses for kinks and leaks. Bled the system of air. Thermostat is operating at correct temp. It also doesn't matter if the monovalve is plugged in or not. I know it defaults to full heat if unplugged. Was thinking aux. water pump but my problem is opposite of the symptoms for that.
The heat will only stay hot at idle, if you drive the car(or just sit and rev the engine for about 30 seconds) it goes ice cold. The only way to make it warm again is shut off the car and start it back up. But don't rev the engine past idle, you'll lose all heat. I'm almost ready to rip all that shit out and put in a regular old manual valve. If anyone has any info on what else can be done before I get to that point, please share.
Got another new piece of info. If I remove the radiator cap so the system can't build pressure I get full all heat and it never gets cold. Left the cap loose and went for drive for about 20 min. Never lost abit of heat. Got out put the cap back on properly and drove for about 5 minutes and lost all heat.
RE: Heater problems - Simpler=Better - 11-29-2012
Year/model? Sounds like a vacuum issue. Blocking off the vac line from under the hood will give you dedicated defroster, but worth a check. Also check your aux pump-they're almost always frozen.
For the winter I ran some cheapo heater hose to bypass the aux pump and monovalve. Cheap, barbaric, and effective.
RE: Heater problems - larsalan - 11-29-2012
'The only way to make it warm again is shut off the car and start it back up'
I had that happen on my car for a while. I think I found that the key/ignition tumbler was turning too far to the right. And thus setting some electric stuff to an off position. All I need to do was turn it back to the left like 1-2mm not actually turn the whole car off.
But, that may not be your problem. Maybe some stuff is stuck in the fluid? Like rust blocking up the heater core?
RE: Heater problems - jandamerc - 11-29-2012
(11-29-2012, 08:41 AM)Simpler=Better Year/model? Sounds like a vacuum issue. Blocking off the vac line from under the hood will give you dedicated defroster, but worth a check. Also check your aux pump-they're almost always frozen.
For the winter I ran some cheapo heater hose to bypass the aux pump and monovalve. Cheap, barbaric, and effective.
Thanx for your input but I'm trying to figure out how it could involve a vacuum issue. The a/c control panel is working correctly if thats what you mean. and I can change the temp from cold to hot with no problems as long as the engine has been left to idle.
Got some new info. Went for drive and pushed it pretty hard. when the engine reached about 4k rpm's it started blowing heat and then after about 30 seconds of normal driving it blows cold again.
It is acting exactly like it has an air blockage. but I swear I have probably wasted 7-8 gallons of deisel trying to bleed this thing.
RE: Heater problems - DeliveryValve - 11-29-2012
Usually no heat while driving indicates a monovalve issue. Since you rebuilt it and checked to see if the diaphragms are not ripped. You'll need to see if your getting power to it and that the power to it is activating it.
.
RE: Heater problems - jandamerc - 11-29-2012
(11-29-2012, 11:56 AM)DeliveryValve Usually no heat while driving indicates a monovalve issue. Since you rebuilt it and checked to see if the diaphragms are not ripped. You'll need to see if your getting power to it and that the power to it is activating it.
.
Sorry, should've mentioned that I've done that also and all is good.
Got another new piece of info. If I remove the radiator cap so the system can't build pressure I get full all heat and it never gets cold. Left the cap loose and went for drive for about 20 min. Never lost abit of heat. Got out put the cap back on properly and drove for about 5 minutes and lost all heat.
RE: Heater problems - Simpler=Better - 11-29-2012
Aux pump. Bypass the monovalve and aux pump with a long piece of heater hose and report back
RE: Heater problems - jandamerc - 11-29-2012
(11-29-2012, 12:54 PM)Simpler=Better Aux pump. Bypass the monovalve and aux pump with a long piece of heater hose and report back
Will try this weekend while I'm doing the valve adjustment and let you guys know. Thx help guys.
RE: Heater problems - DirtDiesel - 11-30-2012
i just recently took off tore apart cleaned out filth and put the aux pump back in (it was not even turning before and had power to it) it solved my issue
RE: Heater problems - Simpler=Better - 11-30-2012
(11-30-2012, 03:14 AM)DirtDiesel i just recently took off tore apart cleaned out filth and put the aux pump back in (it was not even turning before and had power to it) it solved my issue
Also, FUSE THE AUX PUMP. If it seizes it can draw enough power to damage the climate control unit. A cheap 1A fuse & holder inline at the pump is cheap insurance.
RE: Heater problems - jandamerc - 12-02-2012
O.K. I didn't mention that this was on a w126 300sd, so the aux water pump is a pain in the ass to get to and you've got to remove the monovalve assembly along with it. SO. I took all that out and tested the aux pump once I had it out. It functioned flawlessly and wasn't gummed up or anything. I wasn't about to put all that back in there being something in the mix didn't funtion properly and I couldn't figure out why so to fix my problem I went to the parts store and purchased the following:
2 ft. 5/8 heater hose
2 ft. 3/4 heater hose
2 5/8 90 deg. elbows
2 3/4 90 deg. elbows
1 3/4 T-fitting
1 5/8-3/4 fitting
1 box hose clamps
1 3/4 12v. 2 way heater valve- normaly closed
Total price. $58
Took about an hour and half and I totaly done away with everything that was originaly there and wired the new heater valve to the plug that originaly operated the monovalve.
Result: Blistering heat whenever I want it and cold air whenever I want. It works flawlessly.
RE: Heater problems - Simpler=Better - 12-03-2012
Glad to hear you got it working
Thanks for reporting back-lots of people fix their problem and disappear
RE: Heater problems - Mark_M - 01-06-2013
I take it that this is an on off deal and you don't have variable heat settings now?
RE: Heater problems - jandamerc - 01-25-2013
(01-06-2013, 07:10 PM)Mark_M I take it that this is an on off deal and you don't have variable heat settings now?
12v valve only opens fully when a full 12 volts is applied. The heater control sends variable voltage based on where you set it, aka the valve only opens fully when the heater set to maximum. It works the same as if it was the factory stuff only its simpler. Who really cares anyway though. Its not like people actually ride around with thier climate control set at one temperature. I guarentee almost everyone on the forum sets that shit to max when they first get in and then 10 min. later they turn it OFF. lol.
RE: Heater problems - Simpler=Better - 01-25-2013
(01-25-2013, 08:36 AM)jandamerc(01-06-2013, 07:10 PM)Mark_M I take it that this is an on off deal and you don't have variable heat settings now?
12v valve only opens fully when a full 12 volts is applied. The heater control sends variable voltage based on where you set it, aka the valve only opens fully when the heater set to maximum. It works the same as if it was the factory stuff only its simpler. Who really cares anyway though. Its not like people actually ride around with thier climate control set at one temperature. I guarentee almost everyone on the forum sets that shit to max when they first get in and then 10 min. later they turn it OFF. lol.
Yup
