W124 poor heating

[mabbs]

My W124 300D 1990 started with the worst heating I have ever known, including series Land Rovers. Heating became progressively worse with speed.

To date I have:
1. Flushed the entire system with radflush, replaced the coolant, to no avail;
2. Replaced the thermostat.

After having done this with the temp guage at 80-85 degrees I now have no heating whatsoever; suspecting an airlock I bleed, refilled with the top rad hose lose,and once done with the engine running I loosened the heater pipe in the battery corner to allow air to escape. All to no avail.

This must be therefore be a duo valve problem or the matrix is blocked. Having taken the former apart and seen some of the gunk and put it back together, still nothing.

What do I do? Any further diags I can do with my multimeter on the valve, or is it the matrix blocked?

Any suggestions would be much appreciated!

Rich

 

[mercedes13156]

No heating?

Try pulling the pollen filter out. It's above the passenger's feet in the front footwell. Unscrew the panel and pull the sliders apart, it should drop out. If it's black, throw it away. End of problem.

Let me know if it works. it did on my C220D.

 

[television]

Can you put your hands on the pipe either side of the duo valve when the heater is turned to hot and feel any temp difference

 

[Bolide]

I don't think there's a pollen filter in the footwell of the W124. There may be a filter on top of the fan in the engine compartment but not all W124s have one fitted. If the fan pushes a reasonable amount of air I wouldn't suspect that

The diesels do a great job of not generating heat. The later cars have a heat exchanger between the oil & water but the 603-engined cars don't have it

Assuming the thermostat is the correct one I'd try disconnecting the rubber pipe to the air sampler in the roof light assembly. This should push the system to full hot and roast you even at speed. If it doesn't I'd suspect the Duovalve or the heater matrix

My 250TD would warm up very nicely so it is possible to get heat in these cars

Nick Froome
www.w124.co.uk

 

[television]

Check item 140

http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=15S&SID=83&SGR=180&SGN=04

 

[mabbs]

Thanks for the suggestions guys.

Having just dismantled the duo valve that appears fine, have a resistance of 13 ohms. Current to the valve when the temp is selected right down is ~13 volts, as when higher, ie more than the car's interior at say 23 degrees or on defrost it goes to 0.87 volts. I imagine a small trickle of voltage is applied between these temps to control water flow from the heater matrix.

Also the small pump which takes coolant back to the block cuts in when temp is turned up.

This leads me to either the heater matrix or the pollen filter tomorrow evening.

Rich

 

[Telegraph-Hill]

Thanks for the suggestions guys.

This leads me to either the heater matrix or the pollen filter tomorrow evening.

Rich

The duo valves must click in operation. By removing the power the valves are constantly open and you may sweat inside the car If not there is a failure in the cooling system e.g. air. If yes it is the heater Electronics (the device with the poti for setting up the temperature. The power drivers or the potis are defective in most cases.

Greez,
Oli
The W124 has a pollen filter from 1992-1996 not the earlier models.

 

[mabbs]

All sorted

blocked heater matrix - filled with sludge. Refused to budge with steam cleaner on low setting attached to in/outlet. Poor maintenance. Change the coolant every two years - saves you a day and half job of ripping out the whole dash and heater/ac box!