S124 Heater Problem

[Rob77]

Driving up to Scotland yesterday, I noticed the heater wasn't working on the driver's side but seems fine on the passenger side.

How's that? Does it have a separate heater matrix for each side or something?

 

[balge]

There is a dividing valve 'duovalve' which controls each side separately, they stick fairly regularly, may just need cleaning rather than replacement.
Its just in front of the brake reservoir.
cheers

 

[Rob77]

Don't duovalves stick in the hot position though?

 

[carat 3.6]

Don't duovalves stick in the hot position though?

They can stick open or closed. Be warned though the screws are very small on those, so be careful not to snap them if you take it apart.

 

[Rob77]

An update on this thread. The garage says it has cleaned the duo valve and it has made no difference.

I was also told a new one is over £450 from the dealer!

I've just had the whole underbody and suspension fixed up/replaced and don't now need a bill like that.

The existing duo valve has PGI-GF 001303884147 stamped on it. Does anyone have a part number or something I can use to find a good second hand item please?

 

[Druk]

Just a thought from a previous life. iirc there is a temp sender embedded in the heater matrix which has a bearing on the settings. Could that maybe be fault??? Or even the temp dial.

 

[Rob77]

Just a thought from a previous life. iirc there is a temp sender embedded in the heater matrix which has a bearing on the settings. Could that maybe be fault??? Or even the temp dial.

That was fast thanks! I do get heat at the passenger side so wouldn't that rule out the matrix or a sender?

The dial? That could be faulty, I'm not sure how I'd know though.

Possible eureka moment though: before this happened, the side of the centre console was hot against my leg and it isn't (or doesn't seem to be) now. That could suggest a dial/matrix issue - no?

 

[Druk]

The matrix is split left and right which is where the duo-valve sends it's water. There are two sensors.

NB...it's ten years since I had anything to do with 124's and memory's fading fast . So it could be bull**** I'm telling you. Better to confirm with carat 3.6 or dw124.

 

[Charles Morgan]

The multivalve diesel has a different duo valve to other W124s so is horribly expensive and difficult to find. Looking up the VIN of my 94 300D comes up with part number A0018303884 for the duo valve.

 

[Rob77]

So, might the previous heat at the driver's side, followed by none, suggest the thermostat at that side has failed.

That being the case, I should track down a new dual core matrix with built in thermostats (Nissens?)?

And while I'm at it, I should try and find a good used duo valve. That way all my options would be covered as the dial could be checked out when replacing the matrix?

Does that sound like a sensible plan?

 

[mejermy]

Suggest you pull the duovalve to establish whether it's just jammed with crud, has a u/s coil, or possibly has a broken plunger stem. I have a OM 605 and OM606, both of which have caused cabin heat problems. I obtained a used duovalve for the OM605, but simply had to swap plungers as one of the originals had broken at the stem. The OM606 required a complete change of duovalve for a used one, as a coil was u/s, but that fixed the problem. In both cases I waited ages until a used one appeared for sale (and, no, 2 didn't come along at the same time!!).
You may also wish to flush the matrix. I have pix of the matrix flush setup, aided by a 3 way garden hose connector, but the attachment icon won't work and allow me to attach them. PM me if you wish to receive.
Bon courage.

 

[Rob77]

Suggest you pull the duovalve to establish whether it's just jammed with crud, has a u/s coil, or possibly has a broken plunger stem. I have a OM 605 and OM606, both of which have caused cabin heat problems. I obtained a used duovalve for the OM605, but simply had to swap plungers as one of the originals had broken at the stem. The OM606 required a complete change of duovalve for a used one, as a coil was u/s, but that fixed the problem. In both cases I waited ages until a used one appeared for sale (and, no, 2 didn't come along at the same time!!).
You may also wish to flush the matrix. I have pix of the matrix flush setup, aided by a 3 way garden hose connector, but the attachment icon won't work and allow me to attach them. PM me if you wish to receive.
Bon courage.

Thank you, PM sent. My car's an OM606, does PGI-GF 001303884147 sound like a part number for me to track down or is that something else?

 

[Druk]

That's not a proper Merc part number which although not far out will be something like Charles posted in #9. PM me your vin and I'll get the correct No.

 

[Rob77]

That's not a proper Merc part number which although not far out will be something like Charles posted in #9. PM me your vin and I'll get the correct No.

Many thanks, pm sent.

 

[Charles Morgan]

What was the part number (keen to see if I was on the ball)?

 

[Druk]

What was the part number (keen to see if I was on the ball)?

Spot on Charles. A001 830 38 84. (btw.. patience laddie. Think I've got nothing better to do Christmas Day?...........You'd be right!

Perversely, in his PM, Rob mentions that his car has dealer fitted aircon [Diablo] (sic). If it had had factory aircon it would have had a mono-valve 830 40 84.

Contrary to perceived thinking; if that 38 84 part number is inputted to EPC part search it comes up as fitted to just about every 124 that was ever...etc etc. Maybe it's not diesel specific after all?



.

 

[Rob77]

Spot on Charles. A001 830 38 84. (btw.. patience laddie. Think I've got nothing better to do Christmas Day?...........You'd be right!

Perversely, in his PM, Rob mentions that his car has dealer fitted aircon [Diablo] (sic). If it had had factory aircon it would have had a mono-valve 830 40 84.

Contrary to perceived thinking; if that 38 84 part number is inputted to EPC part search it comes up as fitted to just about every 124 that was ever...etc etc. Maybe it's not diesel specific after all?

.

There's not a one for sale on eBay just now though, either in the UK or Germany. And strange I was quoted over £450 for a new one.

So, the hunt begins. I'd like to get the garage to fix this so to avoid faffing them about, maybe I should obtain a replacement duo valve and also both temp probes for the matrix. Do you have part numbers for the probes or are they just cheap things I can get from the dealer?

What do you think. They could replace the matrix first and if that didn't fix things then do the probes next.

I have no knowledge of any of this but I'm guessing it's matrix related at the moment.

 

[Druk]

The probe part number is on the PM.

 

[Rob77]

Just had another look on eBay.de and it seems that 65 84 is the most common one. I can't see any 38 84.

 

[Druk]

A001 830 65 84 is an incorrect part number according to the EPC