ml heater problem

[Dec]

Engine residual heat system is what mine is called, fuses in boot and engine bay.
I also have fuses for Automatic Heater Control, whatever that is?

We have differing cars but the thinking should be the same.
Your pump might be ok and it’s perhaps a faulty cabin thermostat that’s stopping the heating working or something else.

Dec

 

[danny4062]

Thanks dec you've been ca great help. I'll check the electrics in the morning and keep you posted. Really appreciate your help

 

[Dec]

If you get a couple of female bullet connectors (if the pins on the pump are round) you could wire the pump up directly to the car battery, that would prove if the pump is good or bad.

Dec

 

[danny4062]

I took the pump off and checked there is current at the wire and there is. The pump appears dead. Just trying to find a reasonably priced replacement. I can see pumps on the internet but although they are the same they have different connectors so may have to fabricate a way around it and get one of those. I dont fancy paying silly money for one. I tried the breakers but seems mercs are quite rare in yards.

 

[Dec]

There will be a part number somewhere on that pump, Google it as other models like W208/W210 probably use that very same pump.
Try… Three Pointed Parts

Dec

 

[danny4062]

Great found one. Should be here by early next week. In the mean time I have removed the impeller part of the pump which has allowed a little more water through and gives a little more warmth than ive had for the past few days. Hope to get it sorted before the bad weather comes. Thanks dec your a gent.

 

[danny4062]

Well. Ive changed the aux heater pump but still no joy. The inlet hose in the top and hose out of the aux pump are hot and the same temp except the top hose that leads to a Y piece just umder the expansion tank. I have again checked the blend motor which moves as I change the engine temp dial back and forth. Still no heat in the car??? Any advice is very much appreciated. Thanks in advance

 

[Dec]

All you can do now is to wire the pump up directly to the battery, if it runs, there should be heat in the cabin after 5 minutes.

Dec

 

[danny4062]

Is there any chance the heater core has a blockage. The top and bottom hose on the pump are the same temp. Its the one that goes to the Y piece thats just warm.

 

[Dec]

It could be blocked or some valve or relay somewhere not operating, you need to eliminate the pump as a suspect you should be able to feel the pump buzz at the plugged in end if it’s working properly.

If something is blocking the flow, the pump will still run but the coolant won’t circulate hence the warm tube further on from the pump.

Dec

 

[danny4062]

Do you know what valve or relay would need to be checked? My air con packed up just at the end of summer as well!!!

 

[Dec]

I just wouldn’t know enough about your car to advise on what’s what, when did you lose the heating, was it at the same time as the air con?

Dec

 

[danny4062]

I bought it in the summer so had no use of the heating. I ran the car through tje summer to around the end of august when the air con packed up. As it got a bit colder I tried the heating and realised it didnt work. Still have a niggly feeling that the heater core has an air lock. The aux pump is fine. Just the tube to the Y peice is cooler than the rest.

 

[Dec]

It might be best to put the car on STAR diagnostic to see if it shows up any electrical faults, might be related to the air con fault.
Depends where you are located, there might be a good independent near you.

Dec

 

[danny4062]

I have checked the hoses and I had it wrong. Both hoses are hot. The aux pump is working . The actuator is fine and connected. I did find mention of a white hose on the rear of the cabin sensor but I cant find anything. Any help is much appreciated.

 

[chrisjj1982]

Hi i got a 2003 ml270cdi and had no heat coming out this morning,I pulled over and popped the bonnet to check hoses and leaks and everything seemed fine.When i left work today the heater was all working as it should,I googled about this during the day and found out that you can reset the heater.What you need to do is start car get it up to temp then turn the temp to the coldest setting for 5mins then to hot and it should blow hot air out.might be worth a try.

 

[Philbask]

Air Lock !

 

[chrisjj1982]

could be air lock do you get any hissing when you remove the cap,also i think there is a pressure valve built into the cap,maybe worth trying a new cap.

 

[streethawk]

Hi i got a 2003 ml270cdi and had no heat coming out this morning,I pulled over and popped the bonnet to check hoses and leaks and everything seemed fine.When i left work today the heater was all working as it should,I googled about this during the day and found out that you can reset the heater.What you need to do is start car get it up to temp then turn the temp to the coldest setting for 5mins then to hot and it should blow hot air out.might be worth a try.

Duo valve maybe.

 

[bes1110]

Seized Duo valve, common fault.