Only hot air blowing on R.H.S W124 1993

[JonathanM]

I have only hot air available on the RHS of my 1993 W124 280E independent of where I set the temeprature thumbwheel. I am not sure if it is the valve for the RHS side that is at fault or the thumbwheel control unit for the RHS. I am also not sure how to get at these items easily and if they can be repaired or only replaced.. How can this problem be pinpointed ?

 

[television]

It will be the valve 53 in the link, there is an article in the DIY section on how to service and repair

http://www.detali.ru/cat/oem_mb2.as...GM=717.440&CT=F&cat=44Q&SID=83&SGR=180&SGN=04


Welcome to the forum

 

[JonathanM]

Thanks Malcolm for the info and the welcome. I had a look at the DIY section and I found the detailed duo valve prcedure for the 210. I am assuming it will be much the same unit in the 124 so just a matter of finding the thing in daylight tomorrow! I'll let you know how I get on.

 

[television]

Thanks Malcolm for the info and the welcome. I had a look at the DIY section and I found the detailed duo valve prcedure for the 210. I am assuming it will be much the same unit in the 124 so just a matter of finding the thing in daylight tomorrow! I'll let you know how I get on.

Yes it is the same more or less and the same principles apply

Good luck with it

 

[star]

Have you check the duo valve is being switch correctly from the control panel?? which can give you the same fault?

 

[JonathanM]

Hi Star, I haven't checked either, I'm a newbie, and that's the dilema I have, to pinpoint if it's the valve or the control switch. Is there a simple way to access the switch and check the voltage out or what should I do ? I can't see the duo-valve in the engine bay either, where should I look ? Thanks again.

 

[wireman]

Stick a DVM or small lamp across the coil terminals, the valve is just in front of the servo under the bonnet and next to the fuse box (kind of above the brake pedal), you do not need to take any bits off to get at it. If the coil has volts on it the valve will close and the heater will become cold. the coil has 3 wires common and one for each side. The lamp/DVM will indicate when the controller is demanding heat so turn it from hot to cold and look for a change of the lamps state. Since you have one good and one bad side comparing the two will help get you oriented as to what is happening.

The control switch is electronic, to access the assembly you take the panel off the centre console, it is held in place by 2 screws above the radio (take that out first) and 2 large nuts behind the control knobs.

The duovalve is where to start, anything else just gets awkward and is probably OK any way. the two heat thumbwheel controls are ordinary radio type volume controls and may benifit from a bit Televisions favorite non drying switch cleaner, you will need to extract the control unit to do this.

 

[JonathanM]

So back to the heat only on the RHS. I took down the duo valve assembly and the little valve on one side looked a bit 'green' on the side that works, the other one was fine, and there doesn't seem to be a blockage. The actuators in the upper half of the valve body are a little bit scuffed but not too bad. Switching on the side that works with the ignition on inside the car, I observed the actuator move outwards, but the other side appeared to do nothing, and there seems to be a much weaker magnetic field, but there is some magnetic field, and if you switch the ignition off with both dials in the cold position and then on again, both valves move outwards but only the good side remains in the outwards position with a continuous magnetic field. Using a small bulb from the glovebox courtesy light I tried to light it up using either side of each field coil at a time, but neither field coil would light it up (unless there is a break in the hook up wires I used). I then also took off the switch side inside the car, cleaned the switch a bit and it made no difference, so I am still a bit stumped. I think I need to get a DMM and measure exactly what voltage is going to each coil.

 

[G MAN]

would swapping them around prove anything here before it gets complicated?

 

[Parrot of Doom]

Yes, swap the pins over and if the fault is at the valve, the heat will remain on the same side of the car. If the fault is at the control unit in the car, the heat will move to the other side.

 

[JonathanM]

That's exactly what I have done now, and the fault is at the valve, as when I crossed the controls over the right side valve still did not work. Should I try to fix the valve or just replace with a used unit, any experiences here of trying to fix the valve itself ?

 

[G MAN]

Did you try swapping over the moving parts (plunger/piston type thing!) from memory they can be cleaned & lubed to work efficiently. I think there's a.. How To.. somewhere on here if you search.I'll be in Mayo ( & down to Galway) in a couple of weeks so if you're stuck for bits just ask.

 

[wireman]

From your commenet about the RHS coil seeming to lack magnetism, check the resistance of the coil it should be same as LHS. You may have a bad connection where the coil wire is joined to the connector.

 

[Bolide]

I believe the position of the plunger in a Duovalve isn't determined by an easily-measurable applied DC voltage. I believe a chopped DC voltage is sent to it and that the mark-space ratio determines the amount the solenoid opens against the return spring. So you won't see the control voltage on a DVM

But the DC resistance of the two sides of the (disconnected) Duovalve should be the same. If one side is o/c or s/c then the winding is fritzed

Nick Froome
www.w124.co.uk

 

[JonathanM]

I have decided to get a duo-valve from a breakers for €50 tested. A lot cheaper than a new one, and it seems the only viable fix having tried all suggestions.

 

[G MAN]

Sensible option & price. Where is the breakers BTW? May come in handy at the Irish MC Org convention whenever that happens!

 

[JonathanM]

Ask for Eric Norton, Norton Motors, Ballinalee, Co. Longford. 00353 (0)43 - 23034

 

[MotardMan]

Will you let us know if the problem is fixed please?

 

[JonathanM]

Yes, I will do, just waiting for the part delivery still.

 

[JonathanM]

The debacle continues. Eric sent the wrong part, he sent an earlier duo-valve that doesn't have a pump, and the housing and seating are different. He is a great guy on the phone but unfortunately extremely slow if you expect him to post stuff, took him 7 days to get round to it... and then it was the wrong part. I am now waiting on the right part, so hopefully before Christmas. The good news that I have is that tomorrow I am getting a complete new exhaust including cat, a job done on the front wings rust, and new brake shoes, so at least I won't sound like an aeroplane even if it is extremely hot in the cabin still