E280 (W124) Auto Est (96) Heating (duo valve)

[JensH]

Heating Update

Hi all,

Experimenting a little today, I have found out that when the AC is apparently on (i.e. 'EC' light OFF) I get what feels like fresh air through the centre vents and definitely no warm air.

Since my manual advises that AC on does heat the centre vents, it occurred to me that, at some point in the past, the 'EC' (AC on or off switch) may have been cross-wired, so that 'EC' on is, in fact, AC on, and vice-versa. This mistake is possible on any toggle switch isn't it?

Seems logical - does it make sense to others? Remember this is the car that had 24 volt indicator warning lamps fitted...

I still think I have a slight under-performance at max heat, which may need some specialist MB input, but I am going to work on the assumption that I am right and see what happens over the next few days.

Thanks for your help, everyone.

Jens

 

[television]

Center vents are cold air only I believe on a 124

 

[JensH]

Centre Vents

Center vents are cold air only I believe on a 124

Malcolm,

I've attached scan from p26 of my manual re "Air Conditioner" (three button control). As you can see, "Notes" says:
"Heated, unheated or cooled air comes from the centre nozzles depending on the temperature selector setting and outdoor temperature."
& goes on to say that in 'EC' mode only unheated air comes through them.

On p23, referencing the non-AC spec "Automatic heater control" (single button for recirculation), it confirms that only unheated air comes out of the centre vents (also attached).

So I think my logic is right for my particular symptoms: the 'EC' switch has been cross-wired and is working the wrong way round because each setting is actually doing the function of the other...

Thanks for your input, as always.

Jens

 

[JensH]

Bit of service history...

Malcolm,

I've attached scan from p26 of my manual re "Air Conditioner" (three button control). As you can see, "Notes" says:
"Heated, unheated or cooled air comes from the centre nozzles depending on the temperature selector setting and outdoor temperature."
& goes on to say that in 'EC' mode only unheated air comes through them.

On p23, referencing the non-AC spec "Automatic heater control" (single button for recirculation), it confirms that only unheated air comes out of the centre vents (also attached).

So I think my logic is right for my particular symptoms: the 'EC' switch has been cross-wired and is working the wrong way round because each setting is actually doing the function of the other...

Thanks for your input, as always.

Jens

And by the way this is from the works invoice history:
28/11/12 - Access and renew air conditioner compressor [Seiko, about £400 worth] after modification to hanging brackets, made up new pipe from evaporator to compressor and fitted as required. Carried out full air conditioning service. Check all operating pressures. Checked complete system for leaks with ultra violet lamp. Checked operation of complete system. Found interior vent temperature is -1º C.
04/06/13 [I bought in October] - After complete dash & console removal, removed coolant hoses, a/c pipes and complete heater box assembly. Replaced heater blower motor and flap rod kit. Refitted all removed parts and secured to spec. Refilled with new anti-freeze and bled system of all air. Carried out air condition service.

So with all that attention, I would have expected few issues, but all this intervention just makes me think that somewhere in those workshop processes the wiring to the switches got muddled...

The lack of high end heat might be that the duo-valve is simply past it. I can't really assess the cool end of the AC until the weather's a bit warmer.

So I think:
1 Crossed-wires 'EC' button;
2 Recon duo-valve might be needed;
3 Check for re-gas of AC.

Jens

p.s. Off to watch Arsenal under-perform v Man U in the wind and rain...

 

[television]

Malcolm,

I've attached scan from p26 of my manual re "Air Conditioner" (three button control). As you can see, "Notes" says:
"Heated, unheated or cooled air comes from the centre nozzles depending on the temperature selector setting and outdoor temperature."
& goes on to say that in 'EC' mode only unheated air comes through them.

On p23, referencing the non-AC spec "Automatic heater control" (single button for recirculation), it confirms that only unheated air comes out of the centre vents (also attached).

So I think my logic is right for my particular symptoms: the 'EC' switch has been cross-wired and is working the wrong way round because each setting is actually doing the function of the other...

Thanks for your input, as always.

Jens

That was the one that I had, guess it was too long ago, thank you

 

[Felix g]

good morning
TELEVISION .......There are a few different ways to check these duo valves, the 3 pin connector has a center pin live plus 12v, each outer pin is for each of the 2 valves. There should be 0 to 12 volt on the valve depending on the setting in the control panel, max heat =12volt.
i flushed 3 times the cooling system i cleaned the valves and cleaned the aux pump. when i checked the voltage pin 1 showed 13v and the 3rd 5 volts with the heating on both sides on max
now in order have a bit of heating in the car i left them valves unplugged.
what would be the cause?
regards
felix

 

[LostKiwi]

good morning
TELEVISION .......There are a few different ways to check these duo valves, the 3 pin connector has a center pin live plus 12v, each outer pin is for each of the 2 valves. There should be 0 to 12 volt on the valve depending on the setting in the control panel, max heat =12volt.
i flushed 3 times the cooling system i cleaned the valves and cleaned the aux pump. when i checked the voltage pin 1 showed 13v and the 3rd 5 volts with the heating on both sides on max
now in order have a bit of heating in the car i left them valves unplugged.
what would be the cause?
regards
felix

Sadly you won't get a reply from Malcolm (Television) as he passed way last August.
http://forums.mercedesclub.org.uk/index.php?threads/malcolm-end-of-an-era.163442/

 

[Felix g]

i fell sorry to hear that. from everyone's messages it seemed to be a great person!
i will try to find the answer to my problem somewere else!
thank you very much

 

[brianbrian]

If you have a leak in the system, you will be losing pressure, I would see to this first.