Help please!! 500SEC no heaters

[MikeT]

I am having a problem with the heaters, the dual valve has been replaced and is working fine, but still no heat, there is a small electric pump fitted just beneath the dual valve, if I disconnect the pump hot water seams to pass through the matrix giving me heat, but if the engine runs anywhere over 1500 rpm the heaters get cold again, so in traffic I have heat and once I start driving it gets cold, with the electric pump connected I have no heat at all, this is beginning to drive me crazy, thank god for the heated seats! I would greatly appreciate anyones thoughts on this matter. could it have something to do with the water pump which was replaced before i bought the car??

Mike
:?

 

[Arnie]

just a crazy thought... is it possible that the pump is fitted the wrong way round or that the power connector to it, if it has two wires, is the wrong way round? It seems that it may not be helping the water flow in the right direction.

 

[MikeT]

not a crazy thought, tried reversing power to electric pump , still no heat, at the moment it is dissconected so i have heat on idle only. dont no what to do next???????????

 

[Arnie]

Hi,

If it is an impeller-type pump (centrifugal), it may be that the pump itself is plumbed-in back to front.

With these pumps reversing the direction of rotation has little effect as they work by centrifugal action. (although they will be more efficient when rotating the correct way.

Does the pump fit the other way around?? Try it.

 

[NormanB]

This is a difficult one - you have my sympathies:

In no order of logicality here are my suggestions bearing in mind I am approaching this from a W124 perspective.

1. Collapsed heater hose internally.
2. Control panel bolloxed - I have read elsewhere that the temp sensor which is up near the rear view mirror on a W124 can get blocked up with stuff and a hoover out helps - do not know where yours is - sorry.
3. Air in system.
4. The 'new bits' you have fitted are duff (not unknown).
5, Climate control (if fitted) is interfering for some reason.

By the way I though the aux pump was only effective while the system was at idle anyway and once the engine got up to 1500rpm ish the flow from the engine driven waterpump was sufficient to feed the heater matrix.

Hope this helpful - but I guess it ain't :wink:

Let us know how you get on

NormanB

PS: I did a search on the American Merc site, nothing quite matches your symptoms but this is fairly close - I did not spend long and I am sure there is more to ferret out on that site - but I will leave that to you.
http://www.mercedesshop.com/shopforum/showthread.php3?s=&threadid=72007

Oh and this one too:
http://www.mercedesshop.com/shopfor...page=15&highlight=heater&pagenumber=1

 

[MikeT]

Thanks for the suggestions lads, will put up a new post once i get to the bottom of it.
Many thanks

 

[MikeT]

Still no heat, anyone have any suggestions??????????

 

[MikeT]

freezing in here!!!

 

[Mikesmerc]

Hi Mike
my brothers 190 has me baffled as well. Replaced heater matrix and worked for a week. Now back to square one, freezing again. Water valves,air dampers and fan working fine. I gave up.
I have a 560 sec could it be anything to do with the climate control, there must be a lot of sensors to determine cabin temp and air flow rate.
Sorry I couldnt be more helpful.
Regards
Mike

 

[MikeT]

is there any chance it could be the water pump, it was recentley replaced and I have been told it may not have enough fins which wouldnt create enough water flow???

 

[CLASSICCOUPE]

Check the value of the thermostat in the engine. See you PM Message. You may have a summer stat or one with the wrong operating temp fitted. Check against owners book or manual. Should be stamped on the side of stat. You may have the wrong one fitted. Any 380-560 SEC BUYING ADVICE OUT THERE PLEASE. DD